Phase II trial of AKT inhibitor MK-2206 in patients with advanced breast cancer who have tumors with PIK3CA or AKT mutations, and/or PTEN loss/PTEN mutation.

BACKGROUND: The PI3K/AKT pathway is activated through PIK3CA or AKT1 mutations and PTEN loss in breast cancer. We conducted a phase II trial with an allosteric AKT inhibitor MK-2206 in patients with advanced breast cancer who had tumors with PIK3CA/AKT1 mutations and/or PTEN loss/mutation. METHODS: The primary endpoint was objective response rate (ORR). Secondary endpoints were 6-month progression-free survival (6 m PFS), predictive and pharmacodynamic markers, safety, and tolerability. Patients had pre-treatment and on-treatment biopsies as well as collection of peripheral blood mononuclear cells (PBMC) and platelet-rich plasma (PRP). Next-generation sequencing, immunohistochemistry, and reverse phase protein arrays (RPPA) were performed. RESULTS: Twenty-seven patients received MK-2206. Eighteen patients were enrolled into the PIK3CA/AKT1 mutation arm (cohort A): 13 had PIK3CA mutations, four had AKT1 mutations, and one had a PIK3CA mutation as well as PTEN loss. ORR and 6 m PFS were both 5.6% (1/18), with one patient with HR+ breast cancer and a PIK3CA E542K mutation experiencing a partial response (on treatment for 36 weeks). Nine patients were enrolled on the PTEN loss/mutation arm (cohort B). ORR was 0% and 6 m PFS was 11% (1/9), observed in a patient with triple-negative breast cancer and PTEN loss. The study was stopped early due to futility. The most common adverse events were fatigue (48%) and rash (44%). On pre-treatment biopsy, PIK3CA and AKT1 mutation status was concordant with archival tissue testing. However, two patients with PTEN loss based on archival testing had PTEN expression on the pre-treatment biopsy. MK-2206 treatment was associated with a significant decline in pAKT S473 and pAKT T308 and PI3K activation score in PBMC and PRPs, but not in tumor biopsies. By IHC, there was no significant decrease in median pAKT S473 or Ki-67 staining, but a drop was observed in both responders. CONCLUSIONS: MK-2206 monotherapy had limited clinical activity in advanced breast cancer patients selected for PIK3CA/AKT1 or PTEN mutations or PTEN loss. This may, in part, be due to inadequate target inhibition at tolerable doses in heavily pre-treated patients with pathway activation, as well as tumor heterogeneity and evolution in markers such as PTEN conferring challenges in patient selection. TRIAL REGISTRATION: ClinicalTrials.gov, NCT01277757 . Registered 13 January 2011.

Selinexor (KPT-330) demonstrates anti-tumor efficacy in preclinical models of triple-negative breast cancer.

BACKGROUND: Selinexor (KPT-330) is an oral agent that has been shown to inhibit the nuclear exporter XPO1. Given the pressing need for novel therapies for triple-negative breast cancer (TNBC), we sought to determine the antitumor effects of selinexor in vitro and in vivo. METHODS: Twenty-six breast cancer cell lines of different breast cancer subtypes were treated with selinexor in vitro. Cell proliferation assays were used to measure the half-maximal inhibitory concentration (IC50) and to test the effects in combination with chemotherapy. In vivo efficacy was tested both as a single agent and in combination therapy in TNBC patient-derived xenografts (PDXs). RESULTS: Selinexor demonstrated growth inhibition in all 14 TNBC cell lines tested; TNBC cell lines were more sensitive to selinexor (median IC50 44 nM, range 11 to 550 nM) than were estrogen receptor (ER)-positive breast cancer cell lines (median IC50 > 1000 nM, range 40 to >1000 nM; P = 0.017). In multiple TNBC cell lines, selinexor was synergistic with paclitaxel, carboplatin, eribulin, and doxorubicin in vitro. Selinexor as a single agent reduced tumor growth in vivo in four of five different TNBC PDX models, with a median tumor growth inhibition ratio (T/C: treatment/control) of 42% (range 31 to 73%) and demonstrated greater antitumor efficacy in combination with paclitaxel or eribulin (average T/C ratios of 27% and 12%, respectively). CONCLUSIONS: Collectively, these findings strongly suggest that selinexor is a promising therapeutic agent for TNBC as a single agent and in combination with standard chemotherapy.

A functional genetic approach identifies the PI3K pathway as a major determinant of trastuzumab resistance in breast cancer.

A large-scale RNA interference screen to discover genes involved in trastuzumab resistance in breast cancer identified only PTEN as a modulator of drug sensitivity. Oncogenic mutants of PIK3CA (activator of the same pathway and frequently mutated in breast cancer) also conferred resistance to trastuzumab in cell culture. In a cohort of 55 breast cancer patients, activation of the PI3K pathway, as judged by the presence of oncogenic PIK3CA mutations or low PTEN expression, was associated with poor prognosis after trastuzumab therapy, and the combined analysis of PTEN and PIK3CA identified twice as many patients at increased risk for progression compared to PTEN alone. Thus, assessment of PI3K pathway activation may provide a biomarker to identify patients unlikely to respond to trastuzumab-based therapy.

Peroxiredoxin-1 protects estrogen receptor α from oxidative stress-induced suppression and is a protein biomarker of favorable prognosis in breast cancer.

INTRODUCTION: Peroxiredoxin-1 (PRDX1) is a multifunctional protein, acting as a hydrogen peroxide (H2O2) scavenger, molecular chaperone and immune modulator. Although differential PRDX1 expression has been described in many tumors, the potential role of PRDX1 in breast cancer remains highly ambiguous. Using a comprehensive antibody-based proteomics approach, we interrogated PRDX1 protein as a putative biomarker in estrogen receptor (ER)-positive breast cancer. METHODS: An anti-PRDX1 antibody was validated in breast cancer cell lines using immunoblotting, immunohistochemistry and reverse phase protein array (RPPA) technology. PRDX1 protein expression was evaluated in two independent breast cancer cohorts, represented on a screening RPPA (n = 712) and a validation tissue microarray (n = 498). In vitro assays were performed exploring the functional contribution of PRDX1, with oxidative stress conditions mimicked via treatment with H2O2, peroxynitrite, or adenanthin, a PRDX1/2 inhibitor. RESULTS: In ER-positive cases, high PRDX1 protein expression is a biomarker of improved prognosis across both cohorts. In the validation cohort, high PRDX1 expression was an independent predictor of improved relapse-free survival (hazard ratio (HR) = 0.62, 95% confidence interval (CI) = 0.40 to 0.96, P = 0.032), breast cancer-specific survival (HR = 0.44, 95% CI = 0.24 to 0.79, P = 0.006) and overall survival (HR = 0.61, 95% CI = 0.44 to 0.85, P = 0.004). RPPA screening of cancer signaling proteins showed that ERα protein was upregulated in PRDX1 high tumors. Exogenous H2O2 treatment decreased ERα protein levels in ER-positive cells. PRDX1 knockdown further sensitized cells to H2O2- and peroxynitrite-mediated effects, whilst PRDX1 overexpression protected against this response. Inhibition of PRDX1/2 antioxidant activity with adenanthin dramatically reduced ERα levels in breast cancer cells. CONCLUSIONS: PRDX1 is shown to be an independent predictor of improved outcomes in ER-positive breast cancer. Through its antioxidant function, PRDX1 may prevent oxidative stress-mediated ERα loss, thereby potentially contributing to maintenance of an ER-positive phenotype in mammary tumors. These results for the first time imply a close connection between biological activity of PRDX1 and regulation of estrogen-mediated signaling in breast cancer.

Implications of functional proteomics in breast cancer.

Breast cancer is one of the major public health problems of the Western world. Recent advances in genomics and gene expression-profiling approaches have enriched our understanding of this heterogeneous disease. However, progress in functional proteomics in breast cancer research has been relatively slow. Allied with genomics, the functional proteomics approach will be important in improving diagnosis through better classification of breast cancer and in predicting prognosis and response to different therapies, including chemotherapy, hormonal therapy, and targeted therapy. In this review, we will present functional proteomic approaches with a focus on the recent clinical implications of utilizing the reverse-phase protein array platform in breast cancer research.

Prospective evaluation of the conversion rate in the receptor status between primary breast cancer and metastasis: results from the GEICAM 2009-03 ConvertHER study.

The objective of this study was to determine the conversion rate of human epidermal growth factor receptor 2 (HER2), estrogen receptor (ER) and progesterone receptor (PR) between primary tumors and metastatic lesions in advanced breast cancer. Patients with suspected diagnosis of locally recurrent or metastatic breast cancer, either at first relapse or after successive disease progressions, who had an appropriately preserved sample from a primary tumor and were scheduled for a biopsy of the recurrent lesion, were included. Blinded determinations of receptor status on paired samples were performed by immunohistochemistry and fluorescence in situ hybridization at a central laboratory and compared with those performed locally. Overall, 196 patients were included and 184 patients were considered evaluable. Reasons for non-evaluability included the inability to perform biopsy (n = 4) or biopsy results showing normal tissue (n = 3), benign disease (n = 3) or a second neoplasia (n = 2). Conversion rates determined at local level were higher than those determined centrally (HER2: 16 vs. 3 %, ER: 21 vs. 13 %, PR: 35 vs. 28 %, respectively). There was substantial agreement regarding the expression of HER2 in primary tumors and metastases, and ER at metastases, between local and central laboratories. PR at any site and ER at primary site showed moderate agreement. Oncologists altered their treatment plans in 31 % of patients whose tumor subtype had changed. These results reinforce the recommendation for performing confirmatory biopsies of metastases, not only to avoid misdiagnosis of breast cancer relapse, but also to optimize treatment (clinicaltrials.gov identifier: NCT01377363).

Advances and future directions in the targeting of HER2-positive breast cancer: implications for the future.

OPINION STATEMENT: The natural history of HER2-positive breast cancer significantly changed in the past 15 years. Form being the most aggressive type of breast cancer, it became treatable with important cure rates. However, with new and successful drugs, resistance emerges. Progress in research and drug development continues to make available effective anti-HER2 therapies. Our challenge today is to use these tools correctly by looking at the data that support the indications of each compound and to continue clinical trial participation.

Residual tumor thickness at the tumor-normal tissue interface predicts the recurrence-free survival in patients with liver metastasis of breast cancer.

Tumor response to neoadjuvant therapy is a significant predictive indicator of recurrence-free survival. We measured tumor response using residual tumor thickness at the tumor-normal tissue interface (TNI) and evaluated its association with outcome in patients with liver metastasis of breast cancer. We included 48 patients who underwent neoadjuvant therapy followed by partial liver resection at MD Anderson Cancer Center between 1997 and 2010. The hematoxylin-eosin-stained tumor sections were evaluated for both pathologic response and the residual tumor thickness at the TNI by 3 pathologists who were blinded to the clinical information, treatment regimen, and patient outcome. The residual tumor thickness at the TNI was correlated with recurrence-free survival using Kaplan-Meier method and log-rank test. Cox proportional hazard model was used to identify predictors of recurrence-free survival. All patients were women with a median age of 43 years. The median duration of follow-up was 52.1 months. Residual tumor thickness less than or equal to 3 mm at the TNI correlated with major pathologic response and was associated with longer recurrence-free survival in both univariate and multivariate analyses. Residual tumor thickness at the TNI predicts recurrence-free survival and provides an objective outcome end point in patients who underwent neoadjuvant therapy and liver resection of metastatic breast cancer. We suggest using both the pathologic response and the residual tumor thickness at the TNI to measure tumor response to therapy to improve accuracy.

Genotype in BRCA-associated breast cancers.

Women with BRCA1 or 2 mutations are at high risk for breast cancer. For BRCA1, a trend of increasing risk has been associated with increasing downstream (3') location for mutations compared to the upstream (5') mutations in the gene. For BRCA2, an increased risk of breast cancer has been associated with mutations outside of the ovarian cancer cluster region (OCCR). We sought to determine the mutation position in BRCA-associated breast cancers and whether or not there was a genotype-phenotype correlation. Breast cancer patients with BRCA1/2 mutations were identified by a search of a prospectively maintained data base. Mutation site, patient, and tumor characteristics were determined through retrospective review. One hundred and sixty-four patients with BRCA1-associated breast cancer and 109 patients with BRCA2-associated breast cancer were identified. Among patients with BRCA1-associated cancers, 86 (52%) had mutations in the 5' half of the gene. Among patients with BRCA2-associated breast cancers, 40 (37%) had OCCR mutations. Although BRCA1-associated tumors were more likely to be ER/PR- than BRCA2-associated cancers (p < 0.0001), there was no difference in the tumor characteristics among BRCA1 or BRCA2-associated cancers based on mutation location. In this single-institution study, over half of BRCA1-associated and over a third of BRCA2-associated breast cancers were associated with putative lower risk mutations. Although we cannot exclude the possibility that mutations in these regions confer a lower relative risk for breast cancer, vigilance in cancer screening and prevention remains necessary. Further studies in genotype/phenotype correlation are needed to individualize prevention strategies.

Bisphosphonates and pathologic complete response to taxane- and anthracycline-based neoadjuvant chemotherapy in patients with breast cancer.

BACKGROUND: Several studies have suggested that bisphosphonates have an antitumor effect. In the current study, the authors sought to evaluate whether the use of bisphosphonates increased the rate of pathological complete response (pCR) in patients with breast cancer. METHODS: The authors identified 1449 patients with breast cancer who were receiving taxane- and anthracycline-based neoadjuvant chemotherapy between 1995 and 2007 at The University of Texas MD Anderson Cancer Center. Patients who received bisphosphonates for osteopenia or osteoporosis while receiving chemotherapy were also identified. The primary outcome was the percentage of patients achieving a pCR. Groups were compared using the chi-square test. A multivariable logistic regression model was fit to examine the relation between the use of bisphosphonates and pCR. An exploratory survival analysis using the Kaplan-Meier method was performed; groups were compared using the log-rank test. RESULTS: Of the 1449 patients included, 39 (2.7%) received bisphosphonates. Those receiving bisphosphonates were older (P < .001) and less likely to be obese (P = .04). The pCR rate was 25.4% in the bisphosphonate group and 16% in the nonbisphosphonate group (P = .11). In the multivariable model, patients treated with bisphosphonates tended to have higher rates of pCR (odds ratio, 2.18; 95% confidence interval, 0.90-5.24); however, the difference was not found to be statistically significant. With a median follow-up of 55 months (range, 3 months-145 months), no differences in disease recurrence or survival were observed. CONCLUSIONS: The use of bisphosphonates at the time of neoadjuvant chemotherapy was not found to be associated with a statistically significant increase in the rates of pCR. The observed estimates suggest a positive effect; however, the small percentage of patients receiving bisphosphonates likely affected the power to detect a statistically significant difference.

A phase 1 study of weekly everolimus (RAD001) in combination with docetaxel in patients with metastatic breast cancer.

BACKGROUND: Inhibition of mammalian target of rapamycin with everolimus may improve the efficacy of taxanes. Everolimus and docetaxel are both metabolized by CYP3A4, which could result in a pharmacokinetic (PK) interaction. METHODS: Fifteen patients with metastatic breast cancer were treated with docetaxel (doses of 40-75 mg/m(2) intravenously on day 1 of a 21-day cycle) in combination with everolimus (doses ranging from 20 to 50 mg orally on days 1 and 8 of a 21-day cycle) in a phase 1 trial using the continuous reassessment method to determine maximum tolerated dose. The first 2 patients developed a dose-limiting toxicity (neutropenic infection), prompting a mandatory dose reduction and PK evaluation of both everolimus and docetaxel for patients enrolled in subsequent dosing cohorts. RESULTS: Fifteen patients were treated. Dose-limiting toxicity included grade 3 mucositis (n = 1), prolonged grade 4 neutropenia (n = 1), and grade 3 infection/febrile neutropenia (n = 3). Day 8 of everolimus was commonly held for neutropenia despite a dose reduction in docetaxel to 40 mg/m(2). Eleven patients underwent complete PK evaluation for everolimus, and 9 patients underwent complete PK evaluation for both everolimus and docetaxel. Widely variable changes in clearance were seen for both drugs, and the study was terminated because of lack of efficacy and concerns regarding toxicity seen with the combination. CONCLUSIONS: Weekly everolimus in combination with docetaxel every 3 weeks was associated with excessive neutropenia and variable clearance of both drugs, making combination therapy unpredictable, even at low doses of both drugs.

Hormone receptor status influences the locoregional benefit of trastuzumab in patients with nonmetastatic breast cancer.

BACKGROUND: Previous studies have shown that hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) status influence the outcome of locoregional treatments. However, the interrelationship of these factors with trastuzumab is unclear. In this study, the role of HR and HER2 status on the locoregional benefit of trastuzumab treatment was investigated in patients with nonmetastatic breast cancer. METHODS: Locoregional outcomes of 5683 women treated at The University of Texas MD Anderson Cancer Center from 2000 to 2008 for invasive breast cancer were analyzed using Kaplan-Meier and Cox regression methods to compare 6 subgroups: HR-positive (HR+)/HER2-negative (HER2-), HR-/HER2- (triple-negative), HR+/HER2+ with or without trastuzumab, and HR-/HER2+ with or without trastuzumab. RESULTS: Overall, locoregional recurrence (LRR) was 5% at 5 years among patients with HER2+ disease. Patients with HR+/HER2+ disease treated with trastuzumab had half the rate of LRR as patients who did not receive trastuzumab, whereas patients with HR-/HER2+ disease had similar rates of LRR regardless of trastuzumab treatment. On Cox regression analysis comparing LRR risk to the cohort with HR+/HER2- disease, only the HR+/HER2+ cohort treated with trastuzumab had similar LRR risk (hazard ratio = 1.24, 95% confidence interval = 0.56-2.73, P = .591). All other subgroups, including the HR+/HER2+ cohort who did not receive trastuzumab, had significantly worse outcomes. LRR risk was highest among patients with triple-negative disease (hazard ratio = 4.73, 95% confidence interval = 3.42-6.54, P < .001). CONCLUSIONS: Among patients with HR+/HER2+ disease, treatment with trastuzumab reduces LRR risk to the more favorable outcome of patients with HR+/HER2- disease. In contrast, the increased LRR risk among patients with HR-/HER2+ disease remains despite treatment with trastuzumab. Additional locoregional strategies are needed in this subgroup of patients.

Triple-negative breast cancer in Hispanic patients: high prevalence, poor prognosis, and association with menopausal status, body mass index, and parity.

BACKGROUND: Triple-negative breast cancer (TNBC) is defined as breast cancer that is negative for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. TNBC represents 15% of all invasive breast cancers, but some studies have suggested that its prevalence differs between races. To the authors' knowledge, no previous studies have determined the prevalence of TNBC and its risk factors among Hispanic women. METHODS: The authors identified 2074 Hispanic women with breast cancer who attended the National Cancer Institute in Mexico City from 1998 to 2008. All histopathologic and immunohistochemical diagnoses were rereviewed by a breast cancer pathologist. The prevalence of TNBC, its association with clinicopathologic characteristics, and its prognostic impact were determined. RESULTS: The median patient age at diagnosis (±standard deviation) was 50 ± 12 years. The overall prevalence of TNBC was 23.1%. Younger age (P < .001), premenopausal status (P = .002), increased parity (P = .029), hormonal contraceptive use (P = .04) high histologic grade (P < .001), and advanced disease (P < .001) were associated independently with TNBC. Postmenopausal patients who had a body mass index (BMI) <25 kg/m(2) (P = .027) or <30 kg/m(2) (P < .001) were more likely to have TNBC. In multivariate analysis, patients with TNBC had a higher risk of locoregional recurrence (LRR), lower disease-free survival (DFS) (hazard ratio, 1.62; 95% confidence interval, 1.13-2.32; P = .009), and a lower cancer-specific survival (CSS) rate (hazard ratio, 1.66; 95% confidence interval, 1.20-2.30; P = .002) than patients with non-TNBC. CONCLUSIONS: The median age at diagnosis of Hispanic women with breast cancer was 11 years younger than the average age reported in the United States. The prevalence of TNBC in this study population was higher than that reported in white women with breast cancer. TNBC was associated with a higher risk of LRR and with lower DFS and CSS than those in patients with non-TNBC.

Triple-negative breast cancer is not a contraindication for breast conservation.

BACKGROUND: Triple-negative breast cancer (TNBC) is an aggressive subtype shown to have a high risk of locoregional recurrence (LRR). The purpose of this study was to determine the impact of operation type on LRR in TNBC patients. METHODS: A total of 1325 patients with TNBC who underwent breast-conserving therapy (BCT) or mastectomy from 1980 to the present were identified. Clinical and pathological factors were compared by the chi-square test. LRR-free survival (LRRFS), distant metastasis-free survival, and overall survival were estimated by the Kaplan-Meier method. Multivariate analysis was performed by the Cox proportional hazard models. RESULTS: BCT was performed in 651 patients (49%) and mastectomy in 674 (51%). The mastectomy group had larger tumors, a higher incidence of lymphovascular invasion, and higher pathologic N stage (all P < 0.001). At 62-month median follow-up, LRR was seen in 170 (26%) in the BCT group and 203 (30%) in the mastectomy group. Five-year LRRFS rates were higher in the BCT group (76% vs. 71%, P = 0.032), as was distant metastasis-free survival (68% vs. 54%, P < 0.0001) and overall survival (74% vs. 63%, P < 0.0001). On multivariate analysis, T stage (hazard ratio [HR] 1.37, P = 0.006), high nuclear grade (HR 1.92, P = 0.002), lymphovascular invasion (HR 1.93, P < 0.0001), close/positive margins (HR 1.89, P < 0.0001), and use of non-anthracycline or taxane-based adjuvant chemotherapy (HR 2.01, P < 0.0001) increased the LRR risk, while age >50 years was protective (HR 0.73, P = 0.007). Operation type (mastectomy vs. BCT, HR 1.07, P = 0.55) was not statistically significant. CONCLUSIONS: BCT is not associated with increased LRR rates compared to mastectomy. TNBC should not be considered a contraindication for breast conservation.

Genomic, Transcriptomic, and Proteomic Profiling of Metastatic Breast Cancer.

PURPOSE: Metastatic breast cancer (MBC) is not curable and there is a growing interest in personalized therapy options. Here we report molecular profiling of MBC focusing on molecular evolution in actionable alterations. EXPERIMENTAL DESIGN: Sixty-two patients with MBC were included. An analysis of DNA, RNA, and functional proteomics was done, and matched primary and metastatic tumors were compared when feasible. RESULTS: Targeted exome sequencing of 41 tumors identified common alterations in TP53 (21; 51%) and PIK3CA (20; 49%), as well as alterations in several emerging biomarkers such as NF1 mutations/deletions (6; 15%), PTEN mutations (4; 10%), and ARID1A mutations/deletions (6; 15%). Among 27 hormone receptor-positive patients, we identified MDM2 amplifications (3; 11%), FGFR1 amplifications (5; 19%), ATM mutations (2; 7%), and ESR1 mutations (4; 15%). In 10 patients with matched primary and metastatic tumors that underwent targeted exome sequencing, discordances in actionable alterations were common, including NF1 loss in 3 patients, loss of PIK3CA mutation in 1 patient, and acquired ESR1 mutations in 3 patients. RNA sequencing in matched samples confirmed loss of NF1 expression with genomic NF1 loss. Among 33 patients with matched primary and metastatic samples that underwent RNA profiling, 14 actionable genes were differentially expressed, including antibody-drug conjugate targets LIV-1 and B7-H3. CONCLUSIONS: Molecular profiling in MBC reveals multiple common as well as less frequent but potentially actionable alterations. Genomic and transcriptional profiling demonstrates intertumoral heterogeneity and potential evolution of actionable targets with tumor progression. Further work is needed to optimize testing and integrated analysis for treatment selection.

Oxidative Phosphorylation Is a Metabolic Vulnerability in Chemotherapy-Resistant Triple-Negative Breast Cancer.

Oxidative phosphorylation (OXPHOS) is an active metabolic pathway in many cancers. RNA from pretreatment biopsies from patients with triple-negative breast cancer (TNBC) who received neoadjuvant chemotherapy demonstrated that the top canonical pathway associated with worse outcome was higher expression of OXPHOS signature. IACS-10759, a novel inhibitor of OXPHOS, stabilized growth in multiple TNBC patient-derived xenografts (PDX). On gene expression profiling, all of the sensitive models displayed a basal-like 1 TNBC subtype. Expression of mitochondrial genes was significantly higher in sensitive PDXs. An in vivo functional genomics screen to identify synthetic lethal targets in tumors treated with IACS-10759 found several potential targets, including CDK4. We validated the antitumor efficacy of the combination of palbociclib, a CDK4/6 inhibitor, and IACS-10759 in vitro and in vivo. In addition, the combination of IACS-10759 and multikinase inhibitor cabozantinib had improved antitumor efficacy. Taken together, our data suggest that OXPHOS is a metabolic vulnerability in TNBC that may be leveraged with novel therapeutics in combination regimens. SIGNIFICANCE: These findings suggest that triple-negative breast cancer is highly reliant on OXPHOS and that inhibiting OXPHOS may be a novel approach to enhance efficacy of several targeted therapies.

Proteomic and transcriptomic profiling reveals a link between the PI3K pathway and lower estrogen-receptor (ER) levels and activity in ER+ breast cancer.

INTRODUCTION: Accumulating evidence suggests that both levels and activity of the estrogen receptor (ER) and the progesterone receptor (PR) are dramatically influenced by growth-factor receptor (GFR) signaling pathways, and that this crosstalk is a major determinant of both breast cancer progression and response to therapy. The phosphatidylinositol 3-kinase (PI3K) pathway, a key mediator of GFR signaling, is one of the most altered pathways in breast cancer. We thus examined whether deregulated PI3K signaling in luminal ER+ breast tumors is associated with ER level and activity and intrinsic molecular subtype. METHODS: We defined two independent molecular signatures of the PI3K pathway: a proteomic (reverse-phase proteomic array) PI3K signature, based on protein measurement for PI3K signaling intermediates, and a PI3K transcriptional (mRNA) signature based on the set of genes either induced or repressed by PI3K inhibitors. By using these signatures, we scored each ER+ breast tumor represented in multiple independent expression-profiling datasets (four mRNA, n = 915; one protein, n = 429) for activation of the PI3K pathway. Effects of PI3K inhibitor BEZ-235 on ER expression and activity levels and cell growth were tested by quantitative real-time PCR and cell proliferation assays. RESULTS: Within ER+ tumors, ER levels were negatively correlated with the PI3K activation scores, both at the proteomic and transcriptional levels, in all datasets examined. PI3K signature scores were also higher in ER+ tumors and cell lines of the more aggressive luminal B molecular subtype versus those of the less aggressive luminal A subtype. Notably, BEZ-235 treatment in four different ER+ cell lines increased expression of ER and ER target genes including PR, and treatment with IGF-I (which signals via PI3K) decreased expression of ER and target genes, thus further establishing an inverse functional relation between ER and PI3K. BEZ-235 had an additional effect on tamoxifen in inhibiting the growth of a number of ER+ cell lines. CONCLUSIONS: Our data suggest that luminal B tumors have hyperactive GFR/PI3K signaling associated with lower ER levels, which has been correlated with resistance to endocrine therapy. Targeting PI3K in these tumors might reverse loss of ER expression and signaling and restore hormonal sensitivity.

Among women who experience a recurrence after postmastectomy radiation therapy irradiation is not associated with more aggressive local recurrence or reduced survival.

Recent pre-clinical models suggest that radiation can promote tumor aggressiveness. We hypothesized that if this were occurring clinically, locoregional recurrences (LRRs) after postmastectomy radiation therapy (PMRT) would lead to lower survival than LRR after mastectomy alone. This study used two independent datasets to compare survival after LRR in women treated with versus without PMRT. Data from 229 LRR cases among 1,500 patients enrolled on prospective trials at the MD Anderson Cancer Center (MDA), and 66 LRR cases among 318 patients enrolled in the British Columbia Cancer Agency (BCCA) PMRT randomized trial were analyzed. In the MDA non-randomized dataset, 189/1031 had LRR after mastectomy alone and 40/469 had LRR after PMRT. In the randomized BC trial dataset, 52/158 had LRR after mastectomy alone and 14/160 had LRR after PMRT. In both datasets, survival was calculated from the time of LRR to death. Analysis of MDA data shows that in all LRR cases regardless of distant metastasis (DM), 5/10-year OS were 50/34% without PMRT and 27/19% after PMRT (P = 0.006). However, PMRT-treated patients had increased risk factors for DM (advanced T and N stages) and more PMRT-treated patients developed DM prior to LRR (63 vs. 34%, P = 0.005). Analyzing only patients will an isolated LRR (without previous or simultaneous, DMV), there was no OS difference between groups (P = 0.33). Analysis of BCCA data shows that distributions of T and N stages were similar in patients with LRR after mastectomy alone versus after PMRT. DM free survival after any LRR and after isolated LRR were similar in mastectomy alone versus PMRT-treated patients (P = 0.75, P = 0.26, respectively). Overall survival after any LRR and after isolated LRR were also similar in the two groups (P = 0.93, P = 0.28, respectively). Patients who develop LRR after mastectomy alone have high rates of DM and poor OS but these rates are not affected by the use of PMRT at the time of primary treatment. These data do not support the hypothesis that irradiation promotes biologically aggressive local recurrences.

Multimodality imaging of triple receptor-negative tumors with mammography, ultrasound, and MRI.

OBJECTIVE: We retrospectively reviewed imaging findings for 44 patients with triple receptor-negative breast carcinomas on mammography, sonography, and MRI to determine the imaging characteristics of triple receptor-negative cancers that may improve diagnosis at the time of presentation. CONCLUSION: Despite their large size at presentation, triple receptor-negative cancers may be occult on mammography or sonography and frequently have benign or indeterminate features. MRI identified all triple receptor-negative cancers and showed features that had a high positive predictive value for malignancy.

A systems approach to analysis of molecular complexity in breast cancer.

In this issue of Clinical Cancer Research, Andre et al. apply high-resolution arrays to elucidate copy number anomalies in breast cancer. They identify distinct copy number anomaly patterns in different breast cancer subtypes that implicate a number of genes as potential therapeutic targets and as potential markers of therapy responsiveness.