Overall Survival with Ribociclib plus Letrozole in Advanced Breast Cancer.

BACKGROUND: In a previous analysis of this phase 3 trial, first-line ribociclib plus letrozole resulted in significantly longer progression-free survival than letrozole alone among postmenopausal patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. Whether overall survival would also be longer with ribociclib was not known. METHODS: Here we report the results of the protocol-specified final analysis of overall survival, a key secondary end point. Patients were randomly assigned in a 1:1 ratio to receive either ribociclib or placebo in combination with letrozole. Overall survival was assessed with the use of a stratified log-rank test and summarized with the use of Kaplan-Meier methods after 400 deaths had occurred. A hierarchical testing strategy was used for the analysis of progression-free survival and overall survival to ensure the validity of the findings. RESULTS: After a median follow-up of 6.6 years, 181 deaths had occurred among 334 patients (54.2%) in the ribociclib group and 219 among 334 (65.6%) in the placebo group. Ribociclib plus letrozole showed a significant overall survival benefit as compared with placebo plus letrozole. Median overall survival was 63.9 months (95% confidence interval [CI], 52.4 to 71.0) with ribociclib plus letrozole and 51.4 months (95% CI, 47.2 to 59.7) with placebo plus letrozole (hazard ratio for death, 0.76; 95% CI, 0.63 to 0.93; two-sided P = 0.008). No new safety signals were observed. CONCLUSIONS: First-line therapy with ribociclib plus letrozole showed a significant overall survival benefit as compared with placebo plus letrozole in patients with HR-positive, HER2-negative advanced breast cancer. Median overall survival was more than 12 months longer with ribociclib than with placebo. (Funded by Novartis; MONALEESA-2 ClinicalTrials.gov number, NCT01958021.).

Author Correction: HER kinase inhibition in patients with HER2- and HER3-mutant cancers.

The 'Competing interests' statement of this Article has been updated; please see the accompanying Amendment. The original Article has not been corrected online.

Adjuvant platinum versus capecitabine for residual, invasive, triple-negative breast cancer: Patient-reported outcomes in ECOG-ACRIN EA1131.

BACKGROUND: Patient-reported outcomes (PROs) are a better tool for evaluating the experiences of patients who have symptomatic, treatment-associated adverse events (AEs) compared with clinician-rated AEs. The authors present PROs assessing health-related quality of life (HRQoL) and treatment-related neurotoxicity for adjuvant capecitabine versus platinum on the Eastern Cooperative Oncology Group-American College of Radiology Imaging Network (ECOG-ACRIN) EA1131 trial (ClinicalTrials.gov identifier NCT02445391). METHODS: Participants completed the National Comprehensive Cancer Network Functional Assessment of Cancer Therapy-Breast Cancer Symptom Index (NFBSI-16) and the Functional Assessment of Cancer Therapy-Gynecologic Oncology Group neurotoxicity subscale (platinum arm only) at baseline, cycle 3 day 1 (C3D1), 6 months, and 15 months. Because of early termination, power was insufficient to test the hypothesis that HRQoL, as assessed by the NFBSI-16 treatment side-effect (TSE) subscale, would be better at 6 and 15 months in the capecitabine arm; all analyses were exploratory. Means were compared by using t-tests or the Wilcoxon rank-sum test, and proportions were compared by using the χ2 test. RESULTS: Two hundred ninety-six of 330 eligible patients provided PROs. The mean NFBSI-16 TSE subscale score was lower for the platinum arm at baseline (p = .02; absolute difference, 0.6 points) and for the capecitabine arm at C3D1 (p = .04; absolute difference, 0.5 points), but it did not differ at other times. The mean change in TSE subscale scores differed between the arms from baseline to C3D1 (platinum arm, 0.15; capecitabine arm, -0.72; p = .03), but not from baseline to later time points. The mean decline in Functional Assessment of Cancer Therapy-Gynecologic Oncology Group neurotoxicity subscale scores exceeded the minimal meaningful change (1.38 points) from baseline to each subsequent time point (all p < .05). CONCLUSIONS: Despite the similar frequency of clinician-rated AEs, PROs identified greater on-treatment symptom burden with capecitabine and complemented clinician-rated AEs by characterizing patients' experiences during chemotherapy.

A randomized phase III double-blind placebo-controlled trial of first-line chemotherapy and trastuzumab with or without bevacizumab for patients with HER2/neu-positive metastatic breast cancer: a trial of the ECOG-ACRIN Cancer Research Group (E1105).

BACKGROUND: In 2008, bevacizumab received accelerated Food and Drug Administration (FDA) approval for use in human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC). Based on the pre-clinical and preliminary clinical activity of the trastuzumab and bevacizumab combination, ECOG-ACRIN E1105 trial was developed to determine if the addition of bevacizumab to a chemotherapy and trastuzumab combination for first-line therapy would improve progression-free survival (PFS) in patients with HER2-positive MBC. FINDINGS: 96 patients were randomized to receive standard first-line chemotherapy and trastuzumab with or without bevacizumab between November 2007 and October 2009, and 93 began protocol therapy. Induction therapy was given for 24 weeks, followed by maintenance trastuzumab with or without bevacizumab. 60% (56/93) began carboplatin and 74% (69/93) completed 6 cycles of induction therapy. Primary endpoint was PFS. Median PFS was 11.1 and 13.8 months for placebo and bevacizumab arms, respectively (hazard ratio [HR] 95%, Confidence Interval [Cl] for bevacizumab vs. placebo: 0.73 [0.43-1.23], p = 0.24), and at a median follow-up of 70.7 months, median survival was 49.1 and 63 months (HR [95% Cl] for OS: 1.09 [0.61-1.97], p = 0.75). The most common toxicities across both arms were neutropenia and hypertension, with left ventricular systolic dysfunction, fatigue, and sensory neuropathy reported more frequently with bevacizumab. CONCLUSIONS: In this trial, the addition of bevacizumab did not improve outcomes in patients with metastatic HER2-positive breast cancer. Although the trial was underpowered due to smaller than anticipated sample size, these findings corroborated other clinical trials during this time. CLINICAL TRIAL INFORMATION: NCT00520975.

HER kinase inhibition in patients with HER2- and HER3-mutant cancers.

Somatic mutations of ERBB2 and ERBB3 (which encode HER2 and HER3, respectively) are found in a wide range of cancers. Preclinical modelling suggests that a subset of these mutations lead to constitutive HER2 activation, but most remain biologically uncharacterized. Here we define the biological and therapeutic importance of known oncogenic HER2 and HER3 mutations and variants of unknown biological importance by conducting a multi-histology, genomically selected, 'basket' trial using the pan-HER kinase inhibitor neratinib (SUMMIT; clinicaltrials.gov identifier NCT01953926). Efficacy in HER2-mutant cancers varied as a function of both tumour type and mutant allele to a degree not predicted by preclinical models, with the greatest activity seen in breast, cervical and biliary cancers and with tumours that contain kinase domain missense mutations. This study demonstrates how a molecularly driven clinical trial can be used to refine our biological understanding of both characterized and new genomic alterations with potential broad applicability for advancing the paradigm of genome-driven oncology.

Targeting CXCR4 abrogates resistance to trastuzumab by blocking cell cycle progression and synergizes with docetaxel in breast cancer treatment.

BACKGROUND: Although trastuzumab and other HER2-targeted therapies have significantly improved survival in patients with HER2 overexpressed or amplified (HER2+) breast cancer, a significant proportion of patients do not respond or eventually develop clinical resistance. Strategies to reverse trastuzumab resistance remain a high clinical priority. We were the first to report the role of CXCR4 in trastuzumab resistance. The present study aims to explore the therapeutic potential of targeting CXCR4 and better understand the associated mechanisms. METHODS: Immunofluorescent staining, confocal microscopy analysis, and immunoblotting were used to analyze CXCR4 expression. BrdU incorporation assays and flow cytometry were used to analyze dynamic CXCR4 expression. Three-dimensional co-culture (tumor cells/breast cancer-associated fibroblasts/human peripheral blood mononuclear cells) or antibody-dependent cellular cytotoxicity assay was used to mimic human tumor microenvironment, which is necessary for testing therapeutic effects of CXCR4 inhibitor or trastuzumab. The FDA-approved CXCR4 antagonist AMD3100, trastuzumab, and docetaxel chemotherapy were used to evaluate therapeutic efficacy in vitro and in vivo. Reverse phase protein array and immunoblotting were used to discern the associated molecular mechanisms. RESULTS: Using a panel of cell lines and patient breast cancer samples, we confirmed CXCR4 drives trastuzumab resistance in HER2+ breast cancer and further demonstrated the increased CXCR4 expression in trastuzumab-resistant cells is associated with cell cycle progression with a peak in the G2/M phases. Blocking CXCR4 with AMD3100 inhibits cell proliferation by downregulating mediators of G2-M transition, leading to G2/M arrest and abnormal mitosis. Using a panel of trastuzumab-resistant cell lines and an in vivo established trastuzumab-resistant xenograft mouse model, we demonstrated that targeting CXCR4 with AMD3100 suppresses tumor growth in vitro and in vivo, and synergizes with docetaxel. CONCLUSIONS: Our findings support CXCR4 as a novel therapeutic target and a predictive biomarker for trastuzumab resistance in HER2+ breast cancer.

Obesity and metabolic syndrome are associated with short-term endocrine therapy resistance in early ER + breast cancer.

PURPOSE: Increased body mass index (BMI) and metabolic syndrome (MS) are associated with increased breast cancer recurrence risk. Whether this is due to intrinsic tumor biology or modifiable factors of the obese state remains incompletely understood. METHODS: Oncotype DX Recurrence Scores of 751 patients were stratified by BMI to assess association with tumor-intrinsic recurrence risk. Cellular proliferation by Ki67 after 10-21 days of presurgical letrozole treatment was used to stratify endocrine therapy response (sensitive-ln(Ki67) < 1; intermediate-ln(Ki67)1-2; resistant-ln(Ki67) > = 2). BMI at the time of surgery and MS variables were collected retrospectively for 143 patients to analyze association between therapy response and BMI/MS. Additionally, PI3K pathway signaling was evaluated by immunohistochemistry of phosphorylated Akt and S6. RESULTS: There was no significant association between BMI and recurrence score (p = 0.99), and risk score distribution was similar across BMI groups. However, BMI was associated with short-term endocrine therapy resistance, with a significant enrichment of intermediate and resistant tumors in patients with obesity (55%, p = 0.0392). Similarly, the relative risk of an endocrine therapy-resistant tumor was 1.4-fold greater for patients with MS (p = 0.0197). In evaluating PI3K pathway mediators, we found patients with 3 or more MS criteria had more tumors with pAkt scores above the median (p = 0.0436). There were no significant differences in S6 activation. CONCLUSION: Our findings suggest the association between obesity/metabolic syndrome and breast cancer recurrence is better reflected by response to treatment than tumor-intrinsic properties, suggesting interventions to reverse obesity and/or MS may improve outcomes for breast cancer recurrence.

The oral selective estrogen receptor degrader GDC-0810 (ARN-810) in postmenopausal women with hormone receptor-positive HER2-negative (HR + /HER2 -) advanced/metastatic breast cancer.

PURPOSE: GDC-0810 (ARN-810) is a novel, non-steroidal, orally bioavailable, selective estrogen receptor degrader (SERD) that potentially inhibits ligand-dependent and ligand-independent estrogen receptor (ER)-mediated signaling. METHODS: A phase Ia/Ib/IIa dose escalation, combination treatment with palbociclib or a luteinizing hormone-releasing hormone, and expansion study determined the safety, pharmacokinetics, and recommended phase 2 dose (RP2D) of GDC-0810 in postmenopausal women with ER + (HER2 -) locally advanced or metastatic breast cancer (MBC). Baseline plasma ctDNA samples were analyzed to determine the ESR1 mutation status. RESULTS: Patients (N = 152) received GDC-0810 100-800 mg once daily (QD) or 300-400 mg twice daily, in dose escalation, expansion, as single agent or combination treatment. Common adverse events regardless of attribution to study drug were diarrhea, nausea, fatigue, vomiting, and constipation. There was one dose-limiting toxicity during dose escalation. The maximum tolerated dose was not reached. GDC-0810 600 mg QD taken with food was the RP2D. Pharmacokinetics were predictable. FES reduction (> 90%) highlighting pharmacodynamic engagement of ER was observed. Outcomes for the overall population and for patients with tumors harboring ESR1 mutations included partial responses (4% overall; 4% ESR1), stable disease (39% overall; 42% ESR1), non-complete response/non-progressive disease (13% overall; 12% ESR1), progressive disease (40% overall; 38% ESR1), and missing/unevaluable (5% overall; 5% ESR1). Clinical benefit (responses or SD, lasting ≥ 24 weeks) was observed in patients in dose escalation (n = 16, 39%) and expansion (n = 24, 22%). CONCLUSION: GDC-0810 was safe and tolerable with preliminary anti-tumor activity in heavily pretreated patients with ER + advanced/MBC, with/without ESR1 mutations, highlighting the potential for oral SERDs. Clinical Trial and registration date April 4, 2013. NCT01823835 .

Combined Dusp4 and p53 loss with Dbf4 amplification drives tumorigenesis via cell cycle restriction and replication stress escape in breast cancer.

AIM: Deregulated signaling pathways are a hallmark feature of oncogenesis and driver of tumor progression. Dual specificity protein phosphatase 4 (DUSP4) is a critical negative regulator of the mitogen-activated protein kinase (MAPK) pathway and is often deleted or epigenetically silenced in tumors. DUSP4 alterations lead to hyperactivation of MAPK signaling in many cancers, including breast cancer, which often harbor mutations in cell cycle checkpoint genes, particularly in TP53. METHODS: Using a genetically engineered mouse model, we generated mammary-specific Dusp4-deleted primary epithelial cells to investigate the necessary conditions in which DUSP4 loss may drive breast cancer oncogenesis. RESULTS: We found that Dusp4 loss alone is insufficient in mediating tumorigenesis, but alternatively converges with loss in Trp53 and MYC amplification to induce tumorigenesis primarily through chromosome 5 amplification, which specifically upregulates Dbf4, a cell cycle gene that promotes cellular replication by mediating cell cycle checkpoint escape. CONCLUSIONS: This study identifies a novel mechanism for breast tumorigenesis implicating Dusp4 loss and p53 mutations in cellular acquisition of Dbf4 upregulation as a driver of cellular replication and cell cycle checkpoint escape.

Phase 2 study of buparlisib (BKM120), a pan-class I PI3K inhibitor, in patients with metastatic triple-negative breast cancer.

BACKGROUND: Treatment options for triple-negative breast cancer remain limited. Activation of the PI3K pathway via loss of PTEN and/or INPP4B is common. Buparlisib is an orally bioavailable, pan-class I PI3K inhibitor. We evaluated the safety and efficacy of buparlisib in patients with metastatic triple-negative breast cancer. METHODS: This was a single-arm phase 2 study enrolling patients with triple-negative metastatic breast cancer. Patients were treated with buparlisib at a starting dose of 100 mg daily. The primary endpoint was clinical benefit, defined as confirmed complete response (CR), partial response (PR), or stable disease (SD) for ≥ 4 months, per RECIST 1.1. Secondary endpoints included progression-free survival (PFS), overall survival (OS), and toxicity. A subset of patients underwent pre- and on-treatment tumor tissue biopsies for correlative studies. RESULTS: Fifty patients were enrolled. Median number of cycles was 2 (range 1-10). The clinical benefit rate was 12% (6 patients, all SD ≥ 4 months). Median PFS was 1.8 months (95% confidence interval [CI] 1.6-2.3). Median OS was 11.2 months (95% CI 6.2-25). The most frequent adverse events were fatigue (58% all grades, 8% grade 3), nausea (34% all grades, none grade 3), hyperglycemia (34% all grades, 4% grade 3), and anorexia (30% all grades, 2% grade 3). Eighteen percent of patients experienced depression (12% grade 1, 6% grade 2) and anxiety (10% grade 1, 8% grade 2). Alterations in PIK3CA/AKT1/PTEN were present in 6/27 patients with available targeted DNA sequencing (MSK-IMPACT), 3 of whom achieved SD as best overall response though none with clinical benefit ≥ 4 months. Of five patients with paired baseline and on-treatment biopsies, reverse phase protein arrays (RPPA) analysis demonstrated reduction of S6 phosphorylation in 2 of 3 patients who achieved SD, and in none of the patients with progressive disease. CONCLUSIONS: Buparlisib was associated with prolonged SD in a very small subset of patients with triple-negative breast cancer; however, no confirmed objective responses were observed. Downmodulation of key nodes in the PI3K pathway was observed in patients who achieved SD. PI3K pathway inhibition alone may be insufficient as a therapeutic strategy for triple-negative breast cancer. TRIAL REGISTRATION: NCT01790932 . Registered on 13 February 2013; NCT01629615 . Registered on 27 June 2012.

The H1047R PIK3CA oncogene induces a senescence-like state, pleiotropy and acute HSP90 dependency in HER2+ mammary epithelial cells.

In pre-clinical models, co-existence of Human Epidermal Growth Factor Receptor-2 (HER2)-amplification and PI3K catalytic subunit (PIK3CA) mutations results in aggressive, anti-HER2 therapy-resistant breast tumors. This is not always reflected in clinical setting. We speculated that the complex interaction between the HER2 and PIK3CA oncogenes is responsible for such inconsistency. We performed series of biochemical, molecular and cellular assays on genetically engineered isogenic mammary epithelial cell lines and breast cancer cells expressing both oncogenes. In vitro observations were validated in xenografts models. We showed that H1047R, one of the most common PIK3CA mutations, is responsible for endowing a senescence-like state in mammary epithelial cells overexpressing HER2. Instead of imposing a permanent growth arrest characteristic of oncogene-induced senescence, the proteome secreted by the mutant cells promotes stem cell enrichment, angiogenesis, epithelial-to-mesenchymal transition, altered immune surveillance and acute vulnerability toward HSP90 inhibition. We inferred that the pleiotropism, as observed here, conferred by the mutated oncogene, depending on the host microenvironment, contributes to conflicting pre-clinical and clinical characteristics of HER2+, mutated PIK3CA-bearing tumor cells. We also came up with a plausible model for evolution of breast tumors from mammary epithelial cells harboring these two molecular lesions.

Elacestrant (RAD1901) exhibits anti-tumor activity in multiple ER+ breast cancer models resistant to CDK4/6 inhibitors.

BACKGROUND: Addition of CDK4/6 inhibitors (CDK4/6i) to endocrine therapy significantly increased progression-free survival, leading to their approval and incorporation into the metastatic breast cancer treatment paradigm. With these inhibitors being routinely used for patients with advanced estrogen receptor-positive (ER+) breast cancer, resistance to these agents and its impact on subsequent therapy needs to be understood. Considering the central role of ER in driving the growth of ER+ breast cancers, and thus endocrine agents being a mainstay in the treatment paradigm, the effects of prior CDK4/6i exposure on ER signaling and the relevance of ER-targeted therapy are important to investigate. The objective of this study was to evaluate the anti-tumor activity of elacestrant, a novel oral selective estrogen receptor degrader (SERD), in preclinical models of CDK4/6i resistance. METHODS: Elacestrant was evaluated as a single agent, and in combination with alpelisib or everolimus, in multiple in vitro models and patient-derived xenografts that represent acquired and "de novo" CDK4/6i resistance. RESULTS: Elacestrant demonstrated growth inhibition in cells resistant to all three approved CDK4/6i (palbociclib, abemaciclib, ribociclib) in both ESR1 wild-type and mutant backgrounds. Furthermore, we demonstrated that elacestrant, as a single agent and in combination, inhibited growth of patient-derived xenografts that have been derived from a patient previously treated with a CDK4/6i or exhibit de novo resistance to CDK4/6i. While the resistant lines demonstrate distinct alterations in cell cycle modulators, this did not affect elacestrant's anti-tumor activity. In fact, we observe that elacestrant downregulates several key cell cycle players and halts cell cycle progression in vitro and in vivo. CONCLUSIONS: We demonstrate that breast cancer tumor cells continue to rely on ER signaling to drive tumor growth despite exposure to CDK4/6i inhibitors. Importantly, elacestrant can inhibit this ER-dependent growth despite previously reported mechanisms of CDK4/6i resistance observed such as Rb loss, CDK6 overexpression, upregulated cyclinE1 and E2F1, among others. These data provide a scientific rationale for the evaluation of elacestrant in a post-CDK4/6i patient population. Additionally, elacestrant may also serve as an endocrine backbone for rational combinations to combat resistance.

Exploring Biomarkers of Phosphoinositide 3-Kinase Pathway Activation in the Treatment of Hormone Receptor Positive, Human Epidermal Growth Receptor 2 Negative Advanced Breast Cancer.

Resistance to endocrine therapy (ET) is common in patients with hormone receptor positive (HR+) advanced breast cancer (ABC). Consequently, new targeted treatment options are needed in the post-ET setting, with validated biomarkers to inform treatment decisions. Hyperactivation of the phosphoinositide 3-kinase (PI3K) signaling pathway is common in ABC and is implicated in resistance to ET. The most frequent mechanism of PI3K pathway activation is activating mutations or amplification of PIK3CA, which encodes the α-isoform of the catalytic subunit of PI3K. Combining buparlisib, a pan-PI3K-targeted agent, with ET demonstrated modest clinical benefits in patients with aromatase inhibitor-resistant, HR+, human epidermal growth receptor 2 negative (HER2-) ABC in two phase III trials. Importantly, greater efficacy gains were observed in individuals with PIK3CA-mutated disease versus PIK3CA-wild-type tumors. Although the challenging safety profile did not support widespread use of this treatment combination, isoform-selective PI3K inhibitors may improve tolerability. In early clinical trials, promising disease control benefits were demonstrated with the PI3K isoform-selective inhibitors alpelisib and taselisib in patients with PIK3CA-mutated HR+, HER2- ABC. Ongoing biomarker-guided phase II/III studies may provide further opportunities to identify patients most likely to benefit from treatment with PI3K inhibitors and provide insight into optimizing the therapeutic index of PI3K inhibitors. Challenges facing the implementation of routine PIK3CA mutation testing must be addressed promptly so robust and reproducible genotyping can be obtained with liquid and tumor biopsies in a timely and cost-effective manner. IMPLICATIONS FOR PRACTICE: The development of phosphoinositide 3-kinase (PI3K) inhibitors, especially those that selectively target isoforms, may be an effective strategy for overcoming endocrine therapy resistance in hormone receptor positive, human epidermal growth receptor 2 negative advanced breast cancer. Early-phase studies have confirmed that patients with PIK3CA mutations respond best to PI3Kα-isoform inhibition. Ongoing phase III trials will provide further data regarding the efficacy and safety of PI3K inhibitors in patients with different biomarker profiles.

Ribociclib as First-Line Therapy for HR-Positive, Advanced Breast Cancer.

BACKGROUND: The inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) could potentially overcome or delay resistance to endocrine therapy in advanced breast cancer that is positive for hormone receptor (HR) and negative for human epidermal growth factor receptor 2 (HER2). METHODS: In this randomized, placebo-controlled, phase 3 trial, we evaluated the efficacy and safety of the selective CDK4/6 inhibitor ribociclib combined with letrozole for first-line treatment in 668 postmenopausal women with HR-positive, HER2-negative recurrent or metastatic breast cancer who had not received previous systemic therapy for advanced disease. We randomly assigned the patients to receive either ribociclib (600 mg per day on a 3-weeks-on, 1-week-off schedule) plus letrozole (2.5 mg per day) or placebo plus letrozole. The primary end point was investigator-assessed progression-free survival. Secondary end points included overall survival, overall response rate, and safety. A preplanned interim analysis was performed on January 29, 2016, after 243 patients had disease progression or died. Prespecified criteria for superiority required a hazard ratio of 0.56 or less with P<1.29×10-5. RESULTS: The duration of progression-free survival was significantly longer in the ribociclib group than in the placebo group (hazard ratio, 0.56; 95% CI, 0.43 to 0.72; P=3.29×10-6 for superiority). The median duration of follow-up was 15.3 months. After 18 months, the progression-free survival rate was 63.0% (95% confidence interval [CI], 54.6 to 70.3) in the ribociclib group and 42.2% (95% CI, 34.8 to 49.5) in the placebo group. In patients with measurable disease at baseline, the overall response rate was 52.7% and 37.1%, respectively (P<0.001). Common grade 3 or 4 adverse events that were reported in more than 10% of the patients in either group were neutropenia (59.3% in the ribociclib group vs. 0.9% in the placebo group) and leukopenia (21.0% vs. 0.6%); the rates of discontinuation because of adverse events were 7.5% and 2.1%, respectively. CONCLUSIONS: Among patients receiving initial systemic treatment for HR-positive, HER2-negative advanced breast cancer, the duration of progression-free survival was significantly longer among those receiving ribociclib plus letrozole than among those receiving placebo plus letrozole, with a higher rate of myelosuppression in the ribociclib group. (Funded by Novartis Pharmaceuticals; ClinicalTrials.gov number, NCT01958021 .).

The PI3K/AKT Pathway as a Target for Cancer Treatment.

Anticancer targeted therapies are designed to exploit a particular vulnerability in the tumor, which in most cases results from its dependence on an oncogene and/or loss of a tumor suppressor. Genes in the phosphoinositide 3-kinase (PI3K)/AKT pathway are the most frequently altered in human cancers. Aberrant activation of this pathway, as a result of these somatic alterations, is associated with cellular transformation, tumorigenesis, cancer progression, and drug resistance. Several drugs targeting PI3K/ATK are currently in clinical trials, alone or in combination, in both solid tumors and hematologic malignancies. These drugs are the focus of this review.

Ribociclib plus letrozole versus letrozole alone in patients with de novo HR+, HER2- advanced breast cancer in the randomized MONALEESA-2 trial.

PURPOSE: Determine the efficacy and safety of first-line ribociclib plus letrozole in patients with de novo advanced breast cancer. METHODS: Postmenopausal women with HR+ , HER2- advanced breast cancer and no prior systemic therapy for advanced disease were enrolled in the Phase III MONALEESA-2 trial (NCT01958021). Patients were randomized to ribociclib (600 mg/day; 3 weeks-on/1 week-off) plus letrozole (2.5 mg/day; continuous) or placebo plus letrozole until disease progression, unacceptable toxicity, death, or treatment discontinuation. The primary endpoint was investigator-assessed progression-free survival; predefined subgroup analysis evaluated progression-free survival in patients with de novo advanced breast cancer. Secondary endpoints included safety and overall response rate. RESULTS: Six hundred and sixty-eight patients were enrolled, of whom 227 patients (34%; ribociclib plus letrozole vs placebo plus letrozole arm: n = 114 vs. n = 113) presented with de novo advanced breast cancer. Median progression-free survival was not reached in the ribociclib plus letrozole arm versus 16.4 months in the placebo plus letrozole arm in patients with de novo advanced breast cancer (hazard ratio 0.45, 95% confidence interval 0.27-0.75). The most common Grade 3/4 adverse events were neutropenia and leukopenia; incidence rates were similar to those observed in the full MONALEESA-2 population. Ribociclib dose interruptions and reductions in patients with de novo disease occurred at similar frequencies to the overall study population. CONCLUSIONS: Ribociclib plus letrozole improved progression-free survival vs placebo plus letrozole and was well tolerated in postmenopausal women with HR+, HER2- de novo advanced breast cancer.

TGF-ß signaling promotes tumor vasculature by enhancing the pericyte-endothelium association.

BACKGROUND: The breast cancer microenvironment promotes tumor vascularization through the complex interactions involving tumor-associated fibroblasts (TAFs). Emerging data indicate that TAFs increase production and signaling by TGF-ß cytokines, while the role of TGF-ß signaling in the regulation of tumor blood vessels is not fully understood. The current study presents evidence that TAFs enhance the organization of tumor blood capillaries, and TGF-ß signaling plays an important role in this response. METHODS: Tumor vascularization was studied in xenograft models of breast carcinoma cells, alone and in combination with fibroblasts. TGF-ß signaling in breast cancer cells was modulated by expression of kinase-inactive TGFBR1-K232R (dnTGFBR1) or constitutive-active TGFBR1-T204D (caTGFBR1) receptor mutants. The architecture of tumor blood capillaries was assessed by immune-histochemical analysis of endothelium and pericytes. The role of TGF-ß-Smad signaling in fibronectin expression was examined using adenoviral transduction of signaling components. RESULTS: Our studies revealed that TAFs significantly increase the lumen size of blood microvessels. Inactivation of TGF-ß signaling in tumor cells by dnTGFBR1 reduced the microvessel density and lumen sizes, decreasing tumor growth. In contrast, caTGFBR1-tumors exhibited greater vessel density and lumen sizes. Tumors with inactive dnTGFBR1 showed lower amounts of TAFs, while caTGFBR1 increased amounts of TAFs compared to the control. Inspection of pericytes and endothelial cells in tumor vasculature revealed that TAFs enhanced vessel coverage by pericytes, vascular cells supporting capillaries. This effect was impaired in dnTGFBR1-tumors, whereas active caTGFBR1 enhanced the association of pericytes with endothelium. Accordingly, dnTGFBR1-tumors exhibited the presence of hemorrhages, a sign of fragile blood vessels. Biochemical analysis showed that TGFBR1-SMAD signaling up-regulates fibronectin, a prominent regulator of endothelium-pericyte interactions. CONCLUSIONS: The current study indicates that tumor-fibroblast crosstalk enhances tumor vascularization by increasing the pericyte-endothelium association via a mechanism involving the TGFß-fibronectin axis. The tumor-fibroblast model represents a useful system for dissecting the complex interactions governing tumor angiogenesis and developing new approaches to therapeutic targeting tumor vasculature.

The Attenuation Distribution Across the Long Axis of Breast Cancer Liver Metastases at CT: A Quantitative Biomarker for Predicting Overall Survival.

OBJECTIVE: The objective of our study was to compare attenuation distribution across the long-axis (ADLA) measurements, Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, and Choi criteria for predicting overall survival (OS) in patients with metastatic breast cancer treated with bevacizumab. MATERIALS AND METHODS: We obtained HIPAA-compliant data from a prospective, multisite, phase 3 trial of bevacizumab for the treatment of metastatic breast cancer. For patients with one or more liver metastases measuring 15 mm or larger at baseline, we evaluated up to two target liver lesions using RECIST, Choi criteria, and ADLA measurements, with the latter defined as the SD of the CT attenuation values of each pixel along the tumor long-axis diameter. The optimal percentage change threshold for defining an ADLA response was computed by cross-validation analysis in a Cox model. The log-rank test was applied to evaluate RECIST, Choi criteria, and ADLA for discriminating patients with superior OS. The predictive accuracies of all three techniques were compared using Brier scores and areas under the ROC curve (AUC). All analyses were performed separately using best overall response (BOR) and response at the first follow-up time point (FU1). RESULTS: One hundred sixty-four patients met the inclusion criteria. A 25% decrease in the ADLA measurement from baseline was the optimal ADLA response threshold for BOR and FU1. RECIST, Choi criteria, and ADLA successfully identified patients with superior OS when using BOR (RECIST, p = 0.02; Choi and ADLA, p < 0.001), but only Choi criteria and ADLA measurements were successful when using FU1 (RECIST, p = 0.43; Choi and ADLA, p < 0.001). In a direct comparison, ADLA measurements outperformed both RECIST and Choi criteria using BOR (95% CI for Brier score differences, ADLA-RECIST [-0.58 to -0.08] and ADLA-Choi [-0.55 to -0.06]; 95% CI for AUC differences, ADLA-RECIST [0.16-0.33] and ADLA-Choi [0.17-0.36]) as well as using FU1 (95% CI for Brier score differences, ADLA-RECIST [-0.77 to -0.08] and ADLA-Choi [-0.58 to -0.03]; 95% CI for AUC differences, ADLA-RECIST [0.22-0.39] and ADLA-Choi [0.01-0.22]). CONCLUSION: ADLA measurements may be a useful noninvasive indicator of cancer treatment response. Because ADLA measurements may be extracted relatively easily using existing radiologist workflows, further investigation of the ADLA technique is warranted.

Systematic Prioritization of Druggable Mutations in ∼5000 Genomes Across 16 Cancer Types Using a Structural Genomics-based Approach.

A massive amount of somatic mutations has been cataloged in large-scale projects such as The Cancer Genome Atlas (TCGA) and the International Cancer Genome Consortium projects. The majority of the somatic mutations found in tumor genomes are neutral 'passenger' rather than damaging "driver" mutations. Now, understanding their biological consequences and prioritizing them for druggable targets are urgently needed. Thanks to the rapid advances in structural genomics technologies (e.g. X-ray), large-scale protein structural data has now been made available, providing critical information for deciphering functional roles of mutations in cancer and prioritizing those alterations that may mediate drug binding at the atom resolution and, as such, be druggable targets. We hypothesized that mutations at protein-ligand binding-site residues are likely to be druggable targets. Thus, to prioritize druggable mutations, we developed SGDriver, a structural genomics-based method incorporating the somatic missense mutations into protein-ligand binding-site residues using a Bayes inference statistical framework. We applied SGDriver to 746,631 missense mutations observed in 4997 tumor-normal pairs across 16 cancer types from The Cancer Genome Atlas. SGDriver detected 14,471 potential druggable mutations in 2091 proteins (including 1,516 recurrently mutated proteins) across 3558 cancer genomes (71.2%), and further identified 298 proteins harboring mutations that were significantly enriched at protein-ligand binding-site residues (adjusted p value < 0.05). The identified proteins are significantly enriched in both oncoproteins and tumor suppressors. The follow-up drug-target network analysis suggested 98 known and 126 repurposed druggable anticancer targets (e.g. SPOP and NR3C1). Furthermore, our integrative analysis indicated that 13% of patients might benefit from current targeted therapy, and this -proportion would increase to 31% when considering drug repositioning. This study provides a testable strategy for prioritizing druggable mutations in precision cancer medicine.

HER2 missense mutations have distinct effects on oncogenic signaling and migration.

Recurrent human epidermal growth factor receptor 2 (HER2) missense mutations have been reported in human cancers. These mutations occur primarily in the absence of HER2 gene amplification such that most HER2-mutant tumors are classified as "negative" by FISH or immunohistochemistry assays. It remains unclear whether nonamplified HER2 missense mutations are oncogenic and whether they are targets for HER2-directed therapies that are currently approved for the treatment of HER2 gene-amplified breast cancers. Here we functionally characterize HER2 kinase and extracellular domain mutations through gene editing of the endogenous loci in HER2 nonamplified human breast epithelial cells. In in vitro and in vivo assays, the majority of HER2 missense mutations do not impart detectable oncogenic changes. However, the HER2 V777L mutation increased biochemical pathway activation and, in the context of a PIK3CA mutation, enhanced migratory features in vitro. However, the V777L mutation did not alter in vivo tumorigenicity or sensitivity to HER2-directed therapies in proliferation assays. Our results suggest the oncogenicity and potential targeting of HER2 missense mutations should be considered in the context of cooperating genetic alterations and provide previously unidentified insights into functional analysis of HER2 mutations and strategies to target them.