Phase I Study of Fianlimab, a Human Lymphocyte Activation Gene-3 (LAG-3) Monoclonal Antibody, in Combination With Cemiplimab in Advanced Melanoma.

PURPOSE: Coblockade of lymphocyte activation gene-3 (LAG-3) and PD-1 receptors could provide significant clinical benefit for patients with advanced melanoma. Fianlimab and cemiplimab are high-affinity, human, hinge-stabilized IgG4 monoclonal antibodies, targeting LAG-3 and PD-1, respectively. We report results from a first-in-human phase-I study of fianlimab and cemiplimab safety and efficacy in various malignancies including advanced melanoma. METHODS: Patients with advanced melanoma were eligible for enrollment into four cohorts: three for patients without and one for patients with previous anti-PD-1 therapy in the advanced disease setting. Patients were treated with fianlimab 1,600 mg and cemiplimab 350 mg intravenously once every 3 weeks for up to 51 weeks, with an optional additional 51 weeks if clinically indicated. The primary end point was objective response rate (ORR) per RECIST 1.1 criteria. RESULTS: ORRs were 63% for patients with anti-PD-1-naïve melanoma (cohort-6; n = 40; median follow-up 20.8 months), 63% for patients with systemic treatment-naïve melanoma (cohort-15; n = 40; 11.5 months), and 56% for patients with previous neo/adjuvant treatment melanoma (cohort-16; n = 18, 9.7 months). At a median follow-up of 12.6 months for the combined cohorts (6 + 15 + 16), the ORR was 61.2% and the median progression-free survival (mPFS) 13.3 months (95% CI, 7.5 to not estimated [NE]). In patients (n = 13) with previous anti-PD-1 adjuvant therapy, ORR was 61.5% and mPFS 12 months (95% CI, 1.4 to NE). ORR in patients with previous anti-PD-1 therapy for advanced disease (n = 15) was 13.3% and mPFS 1.5 months (95% CI, 1.3 to 7.7). Treatment-emergent and treatment-related adverse events ≥grade 3 (G3) were observed in 44% and 22% of patients, respectively. Except for increased incidence of adrenal insufficiency (12%-G1-4, 4%-G3-4), no new safety signals were recorded. CONCLUSION: The current results show a promising benefit-risk profile of fianlimab/cemiplimab combination for patients with advanced melanoma, including those with previous anti-PD-1 therapy in the adjuvant, but not advanced, setting.

Talazoparib in Patients With Solid Tumors With BRCA1/2 Mutation: Results From the Targeted Agent and Profiling Utilization Registry Study.

PURPOSE: The Targeted Agent and Profiling Utilization Registry Study is a phase II basket trial evaluating the antitumor activity of commercially available targeted agents in patients with advanced cancer and genomic alterations known to be drug targets. Results of a cohort of patients with various solid tumors with germline or somatic BRCA1/2 mutations treated with talazoparib are reported. METHODS: Eligible patients had advanced solid tumors, measurable disease (RECIST), Eastern Cooperative Oncology Group performance status 0-2, adequate organ function, and no standard treatment options. Patients with germline BRCA-mutated human epidermal growth factor receptor 2-negative locally advanced or metastatic breast cancer were not eligible for this study. Primary end point was disease control (DC) determined by investigator assessment of objective response (OR) or stable disease (SD) of at least 16 weeks duration (SD16+). The results were evaluated on the basis of a one-sided exact binomial test with a null DC rate of 15% versus 35% (power = 0.82; α = .10). Secondary end points were OR, progression-free survival, overall survival, duration of response, duration of SD, and safety. RESULTS: Twenty-eight patients (20 cancer types) with BRCA1/2 mutations were enrolled from December 2019 to September 2021 and collapsed into a single histology pooled cohort for analysis. All patients were evaluable for efficacy. One complete response, nine partial response, and six SD16+ were observed for DC and OR rates of 57% (one-sided 90% CI, 43 to 100) and 36% (95% CI, 19 to 56), respectively. The null hypothesis of a 15% DC rate was rejected (P < .001). Patients with OR had the following tumor types: breast (2), nonmelanoma skin, mesothelioma, stomach, uterus, non-small cell lung cancer, ovary, hepatocellular carcinoma, and pancreas. Thirteen patients had at least one grade 3-5 adverse event (AE) or serious AE at least possibly related to talazoparib. All were consistent with the drug label except bilirubin increase and hyponatremia (both grade 3 AEs). CONCLUSION: Talazoparib demonstrated antitumor activity in patients with advanced solid tumors and BRCA1/2 mutations, including cancer types for which poly ADP-ribose polymerase inhibitors are not yet US Food and Drug Administration-approved.

Regorafenib in Patients With Solid Tumors With BRAF Alterations: Results From the Targeted Agent and Profiling Utilization Registry (TAPUR) Study.

PURPOSE: Targeted Agent and Profiling Utilization Registry is a phase II basket trial evaluating the antitumor activity of commercially available targeted agents in patients with advanced cancer with genomic alterations known to be drug targets. Results of a cohort of patients with solid tumors with BRAF alterations treated with regorafenib are reported. METHODS: Eligible patients had measurable disease (RECIST v.1.1), Eastern Cooperative Oncology Group performance status 0-1, adequate organ function, and no standard treatment options. The primary end point was disease control (DC), defined as investigator assessment of patients with complete or partial response (PR) or stable disease of at least 16-weeks duration (SD16+). Low accruing histology-specific cohorts with BRAF alterations treated with regorafenib were collapsed into a single histology-pooled cohort for this analysis. The results were evaluated on the basis of a one-sided exact binomial test with a null DC rate of 15% versus 35% (power, 0.84; α, .10). Secondary end points were objective response (OR), progression-free survival, overall survival, duration of response, duration of stable disease, and safety. RESULTS: Twenty-eight patients with 12 tumor types with BRAF alterations were enrolled from June 2016 to June 2021. All patients were evaluable for efficacy. Two patients with PR and four with SD16+ were observed for DC and OR rates of 21% (90% CI, 12 to 100) and 7% (95% CI, 1 to 24), respectively. The null hypothesis of 15% DC rate was not rejected (P = .24). Eight patients had at least one grade 3 adverse event or serious adverse event at least possibly related to regorafenib. CONCLUSION: Regorafenib did not meet prespecified criteria to declare a signal of activity in patients with solid tumors with BRAF alterations.

Outcomes of patients with resected stage III/IV acral or mucosal melanoma, treated with adjuvant anti-PD-1 based therapy.

IMPORTANCE: Acral (AM) and mucosal melanomas (MM) are rare subtypes with a poor prognosis. In those with advanced disease, anti-PD-1 (PD1) therapy has reduced activity compared to that seen in non-acral cutaneous melanoma. OBJECTIVE: To determine the efficacy of adjuvant PD1 in resected AM or MM. DESIGN: An international, retrospective cohort study SETTING: Data up to November 2021 collected from 20 centres across 10 countries. PARTICIPANTS: One hundred and ninety four patients with resected stage III or IV1 AM or MM who received adjuvant PD1 were included and compared to matched patients from the Melanoma Institute Australia (MIA) database using a propensity score matching analysis. MAIN OUTCOMES AND MEASURES: Recurrence-free survival (RFS), distant metastasis-free survival (DMFS) and overall survival (OS) were investigated. RESULTS: Forty five of 139 (32%) AM and 9 of 55 (16%) MM patients completed adjuvant therapy. The main reason for early treatment cessation in both groups was disease recurrence: 51 (37%) and 30 (55%) in the AM and MM groups, respectively. In the AM group adjuvant PD1 was associated with a longer RFS [HR-0.69 (0.52-0.92, p = 0.0127)], DMFS [HR0.58 (0.38-0.89, p = 0.0134)] and OS [HR of 0.59 (0.38-0.92, p-value 0.0196)] when compared to the historical cohort. In the MM group there was no statistical difference in RFS [HR1.36 (0.69-2.68,p-value 0.3799], DMFS or OS. CONCLUSION AND RELEVANCE: After adjuvant PD1, both AM and MM have a high risk of recurrence. Our data suggests a benefit to using adjuvant PD1 therapy in resected AM but not in resected MM. Additional studies to investigate the efficacy of adjuvant PD1 for MM are needed.

Low booster uptake in cancer patients despite health benefits.

Patients with cancer are at increased risk of death from COVID-19 and have reduced immune responses to SARS-CoV2 vaccines, necessitating regular boosters. We performed comprehensive chart reviews, surveys of patients attitudes, serology for SARS-CoV-2 antibodies and T-cell receptor (TCR) ß sequencing for cellular responses on a cohort of 982 cancer patients receiving active cancer therapy accrued between November-3-2020 and Mar-31-2023. We found that 92·3% of patients received the primer vaccine, 70·8% received one monovalent booster, but only 30·1% received a bivalent booster. Booster uptake was lower under age 50, and among African American or Hispanic patients. Nearly all patients seroconverted after 2+ booster vaccinations (>99%) and improved cellular responses, demonstrating that repeated boosters could overcome poor response to vaccination. Receipt of booster vaccinations was associated with a lower risk of all-cause mortality (HR=0·61, P=0·024). Booster uptake in high-risk cancer patients remains low and strategies to encourage booster uptake are needed. Highlights: COVID-19 booster vaccinations increase antibody levels and maintain T-cell responses against SARS-CoV-2 in patients receiving various anti-cancer therapiesBooster vaccinations reduced all-cause mortality in patientsA significant proportion of patients remain unboosted and strategies are needed to encourage patients to be up-to-date with vaccinations.

Efficacy of anti-PD-1 and ipilimumab alone or in combination in acral melanoma.

BACKGROUND: Acral melanoma is a rare melanoma subtype with poor prognosis. Importantly, these patients were not identified as a specific subgroup in the landmark melanoma trials involving ipilimumab and the anti-programmed cell death protein-1 (PD-1) agents nivolumab and pembrolizumab. There is therefore an absence of prospective clinical trial evidence regarding the efficacy of checkpoint inhibitors (CPIs) in this population. Acral melanoma has lower tumor mutation burden (TMB) than other cutaneous sites, and primary site is associated with differences in TMB. However the impact of this on the effectiveness of immune CPIs is unknown. We examined the efficacy of CPIs in acral melanoma, including by primary site. METHODS: Patients with unresectable stage III/IV acral melanoma treated with CPI (anti-PD-1 and/or ipilimumab) were studied. Multivariable logistic and Cox regression analyses were conducted. Primary outcome was objective response rate (ORR); secondary outcomes were progression-free survival (PFS) and overall survival (OS). RESULTS: In total, 325 patients were included: 234 (72%) plantar, 69 (21%) subungual and 22 (7%) palmar primary sites. First CPI included: 184 (57%) anti-PD-1, 59 (18%) anti-PD-1/ipilimumab combination and 82 (25%) ipilimumab. ORR was significantly higher with initial anti-PD-1/ipilimumab compared with anti-PD-1 (43% vs 26%, HR 2.14, p=0.0004) and significantly lower with ipilimumab (15% vs 26%, HR 0.49, p=0.0016). Landmark PFS at 1 year was highest for anti-PD-1/ipilimumab at 34% (95% CI 24% to 49%), compared with 26% (95% CI 20% to 33%) with anti-PD-1 and 10% (95% CI 5% to 19%) with ipilimumab. Despite a trend for increased PFS, anti-PD-1/ipilimumab combination did not significantly improve PFS (HR 0.85, p=0.35) or OS over anti-PD-1 (HR 1.30, p=0.16), potentially due to subsequent therapies and high rates of acquired resistance. No outcome differences were found between primary sites. CONCLUSION: While the ORR to anti-PD-1/ipilimumab was significantly higher than anti-PD-1 and PFS numerically higher, in this retrospective cohort this benefit did not translate to improved OS. Future trials should specifically include patients with acral melanoma, to help determine the optimal management of this important melanoma subtype.

Immunotherapy of cancer in the era of checkpoint inhibitor.

Application of immunotherapy has revolutionized treatment of number of malignancies. We present a review of immunotherapy approaches, early-phase data of number of new immunotherapeutic targets in melanoma, cutaneous squamous cell carcinoma, Merkel cell cancer, and non-small cell lung cancer.

Longitudinal SARS-CoV-2 mRNA Vaccine-Induced Humoral Immune Responses in Patients with Cancer.

Longitudinal studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine-induced immune responses in patients with cancer are needed to optimize clinical care. In a prospective cohort study of 366 (291 vaccinated) patients, we measured antibody levels [anti-spike (IgG-(S-RBD) and anti-nucleocapsid immunoglobulin] at three time points. Antibody level trajectories and frequency of breakthrough infections were evaluated by tumor type and timing of treatment relative to vaccination. IgG-(S-RBD) at peak response (median = 42 days after dose 2) was higher (P = 0.002) and remained higher after 4 to 6 months (P = 0.003) in patients receiving mRNA-1273 compared with BNT162b2. Patients with solid tumors attained higher peak levels (P = 0.001) and sustained levels after 4 to 6 months (P < 0.001) compared with those with hematologic malignancies. B-cell targeted treatment reduced peak (P = 0.001) and sustained antibody responses (P = 0.003). Solid tumor patients receiving immune checkpoint inhibitors before vaccination had lower sustained antibody levels than those who received treatment after vaccination (P = 0.043). Two (0.69%) vaccinated and one (1.9%) unvaccinated patient had severe COVID-19 illness during follow-up. Our study shows variation in sustained antibody responses across cancer populations receiving various therapeutic modalities, with important implications for vaccine booster timing and patient selection. SIGNIFICANCE: Long-term studies of immunogenicity of SARS-CoV-2 vaccines in patients with cancer are needed to inform evidence-based guidelines for booster vaccinations and to tailor sequence and timing of vaccinations to elicit improved humoral responses.

Fatty Acid Synthase Confers Tamoxifen Resistance to ER+/HER2+ Breast Cancer.

The identification of clinically important molecular mechanisms driving endocrine resistance is a priority in estrogen receptor-positive (ER+) breast cancer. Although both genomic and non-genomic cross-talk between the ER and growth factor receptors such as human epidermal growth factor receptor 2 (HER2) has frequently been associated with both experimental and clinical endocrine therapy resistance, combined targeting of ER and HER2 has failed to improve overall survival in endocrine non-responsive disease. Herein, we questioned the role of fatty acid synthase (FASN), a lipogenic enzyme linked to HER2-driven breast cancer aggressiveness, in the development and maintenance of hormone-independent growth and resistance to anti-estrogens in ER/HER2-positive (ER+/HER2+) breast cancer. The stimulatory effects of estradiol on FASN gene promoter activity and protein expression were blunted by anti-estrogens in endocrine-responsive breast cancer cells. Conversely, an AKT/MAPK-related constitutive hyperactivation of FASN gene promoter activity was unaltered in response to estradiol in non-endocrine responsive ER+/HER2+ breast cancer cells, and could be further enhanced by tamoxifen. Pharmacological blockade with structurally and mechanistically unrelated FASN inhibitors fully impeded the strong stimulatory activity of tamoxifen on the soft-agar colony forming capacity-an in vitro metric of tumorigenicity-of ER+/HER2+ breast cancer cells. In vivo treatment with a FASN inhibitor completely prevented the agonistic tumor-promoting activity of tamoxifen and fully restored its estrogen antagonist properties against ER/HER2-positive xenograft tumors in mice. Functional cancer proteomic data from The Cancer Proteome Atlas (TCPA) revealed that the ER+/HER2+ subtype was the highest FASN protein expressor compared to basal-like, HER2-enriched, and ER+/HER2-negative breast cancer groups. FASN is a biological determinant of HER2-driven endocrine resistance in ER+ breast cancer. Next-generation, clinical-grade FASN inhibitors may be therapeutically relevant to countering resistance to tamoxifen in FASN-overexpressing ER+/HER2+ breast carcinomas.

Fatty Acid Synthase Is a Key Enabler for Endocrine Resistance in Heregulin-Overexpressing Luminal B-Like Breast Cancer.

HER2 transactivation by the HER3 ligand heregulin (HRG) promotes an endocrine-resistant phenotype in the estrogen receptor-positive (ER+) luminal-B subtype of breast cancer. The underlying biological mechanisms that link them are, however, incompletely understood. Here, we evaluated the putative role of the lipogenic enzyme fatty acid synthase (FASN) as a major cause of HRG-driven endocrine resistance in ER+/HER2-negative breast cancer cells. MCF-7 cells engineered to stably overexpress HRG (MCF-7/HRG), an in vitro model of tamoxifen/fulvestrant-resistant luminal B-like breast cancer, showed a pronounced up-regulation of FASN gene/FASN protein expression. Autocrine HRG up-regulated FASN expression via HER2 transactivation and downstream activation of PI-3K/AKT and MAPK-ERK1/2 signaling pathways. The HRG-driven FASN-overexpressing phenotype was fully prevented in MCF-7 cells expressing a structural deletion mutant of HRG that is sequestered in a cellular compartment and lacks the ability to promote endocrine-resistance in an autocrine manner. Pharmacological inhibition of FASN activity blocked the estradiol-independent and tamoxifen/fulvestrant-refractory ability of MCF-7/HRG cells to anchorage-independently grow in soft-agar. In vivo treatment with a FASN inhibitor restored the anti-tumor activity of tamoxifen and fulvestrant against fast-growing, hormone-resistant MCF-7/HRG xenograft tumors in mice. Overall, these findings implicate FASN as a key enabler for endocrine resistance in HRG+/HER2- breast cancer and highlight the therapeutic potential of FASN inhibitors for the treatment of endocrine therapy-resistant luminal-B breast cancer.

Eflapegrastim, a Long-Acting Granulocyte-Colony Stimulating Factor for the Management of Chemotherapy-Induced Neutropenia: Results of a Phase III Trial.

BACKGROUND: Eflapegrastim, a novel, long-acting recombinant human granulocyte-colony stimulating factor (rhG-CSF), consists of a rhG-CSF analog conjugated to a human IgG4 Fc fragment via a short polyethylene glycol linker. Preclinical and phase I and II pharmacodynamic and pharmacokinetic data showed increased potency for neutrophil counts for eflapegrastim versus pegfilgrastim. This open-label phase III trial compared the efficacy and safety of eflapegrastim with pegfilgrastim for reducing the risk of chemotherapy-induced neutropenia. MATERIALS AND METHODS: Patients with early-stage breast cancer were randomized 1:1 to fixed-dose eflapegrastim 13.2 mg (3.6 mg G-CSF) or standard pegfilgrastim (6 mg G-CSF) following standard docetaxel plus cyclophosphamide chemotherapy for 4 cycles. The primary objective was to demonstrate the noninferiority of eflapegrastim compared with pegfilgrastim in mean duration of severe neutropenia (DSN; grade 4) in cycle 1. RESULTS: Eligible patients were randomized 1:1 to study arms (eflapegrastim, n = 196; pegfilgrastim, n = 210). The incidence of cycle 1 severe neutropenia was 16% (n = 31) for eflapegrastim versus 24% (n = 51) for pegfilgrastim, reducing the relative risk by 35% (p = .034). The difference in mean cycle 1 DSN (-0.148 day) met the primary endpoint of noninferiority (p < .0001) and also showed statistical superiority for eflapegrastim (p = .013). Noninferiority was maintained for the duration of treatment (all cycles, p < .0001), and secondary efficacy endpoints and safety results were also comparable for study arms. CONCLUSION: These results demonstrate noninferiority and comparable safety for eflapegrastim at a lower G-CSF dose versus pegfilgrastim. The potential for increased potency of eflapegrastim to deliver improved clinical benefit warrants further clinical study in patients at higher risk for CIN. IMPLICATIONS FOR PRACTICE: Chemotherapy-induced neutropenia (CIN) remains a significant clinical dilemma for oncology patients who are striving to complete their prescribed chemotherapy regimen. In a randomized, phase III trial comparing eflapegrastim to pegfilgrastim in the prevention of CIN, the efficacy of eflapegrastim was noninferior to pegfilgrastim and had comparable safety. Nevertheless, the risk of CIN remains a great concern for patients undergoing chemotherapy, as the condition frequently results in chemotherapy delays, dose reductions, and treatment discontinuations.

A unique case of chronic myeloid leukemia presenting as monocular vision loss with unilateral retinopathy.

PURPOSE: To report a case of unilateral leukemic retinopathy secondary to chronic myeloid leukemia (CML). OBSERVATIONS: Patient presented to clinic with a visual acuity (VA) of 20/200 in the right eye (OD) after several months of progressive monocular vision loss and was found to have dense pre-retinal hemorrhage. Patient underwent 23-gauge pars plana vitrectomy to clear the preretinal hemorrhage along with a complex macula-off retinal detachment repair to address retinal tear and multilayer retinal hemorrhage. The patient was subsequently diagnosed with CML as she was found to be positive for the fusion protein of break point cluster gene (BCR) with Abelson tyrosine kinase (ABL1), BCR-ABL1, upon systemic work-up. Imatinib therapy resulted in complete hematologic and cytogenetic resolution after one month, however, the patient's vision remained unchanged six months after surgery. CONCLUSION AND IMPORTANCE: To the authors' knowledge, this is the first reported case of unilateral leukemic retinopathy secondary to low risk CML, as determined by the Sokal and Hasford prognostic scoring systems. CML should be included in the differential diagnosis of patients with progressive monocular vision loss with suspicious multi-layer retinal compromise.

Endogenous aryl hydrocarbon receptor promotes basal and inducible expression of tumor necrosis factor target genes in MCF-7 cancer cells.

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that upon activation by the toxicant 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) stimulates gene expression and toxicity. AHR is also important for normal mouse physiology and may play a role in cancer progression in the absence of environmental toxicants. The objective of this report was to identify AHR-dependent genes (ADGs) whose expression is regulated by AHR in the absence of toxicants. RNA-Seq analysis revealed that AHR regulated the expression of over 600 genes at an FDR<10% in MCF-7 breast cancer cells upon knockdown with short interfering RNA. Pathway analysis revealed that a significant number of ADGs were components of TCDD and tumor necrosis factor (TNF) pathways. We also demonstrated that siRNA knockdown of AHR modulated TNF induction of MNSOD and cytotoxicity in MCF-7 cells. Collectively, the major new findings of this report are: (1) endogenous AHR promotes the expression of xenobiotic metabolizing enzymes even in the absence of toxicants and drugs, (2) AHR by modulating the basal expression of a large fraction of TNF target genes may prime them for TNF stimulation and (3) AHR is required for TNF induction of MNSOD and the cellular response to cytotoxicity in MCF-7 cells. This latter result provides a potentially new role for AHR in MCF-7 cancer progression as a mediator of TNF and antioxidant responses.

Trastuzumab in combination with heregulin-activated Her-2 (erbB-2) triggers a receptor-enhanced chemosensitivity effect in the absence of Her-2 overexpression.

PURPOSE: The decision for treating breast cancer patients with trastuzumab is based on HER-2 amplification and/or overexpression. METHODS: Using MCF-7 cells (Her-2 +/-) engineered to overexpress heregulin (MCF-7/HRG), a ligand for the Her-2/3/4 network, we investigated whether HRG-induced transactivation of Her-2 affected breast cancer cell sensitivity to chemotherapy and whether trastuzumab trigger receptor-enhanced chemosensitivity (REC) when combined with chemotherapy without Her-2 overexpression. RESULTS: MCF-7/HRG cells were more than 10-fold resistant to the alkylating agent cisplatin (CDDP), while trastuzumab coexposure completely reversed HRG-promoted CDDP resistance. A synergistic interaction between trastuzumab in combination with CDDP (paclitaxel or vincristine) was obtained in MCF-7/HRG cells. Trastuzumab prevented activation of the antiapoptotic and proliferative cascades and inhibited HRG-induced Her-2/3 phosphorylation. CDDP efficacy was enhanced by trastuzumab in cells expressing endogenously high levels of HRG. Conversely, trastuzumab coexposure was ineffective in enhancing chemotherapy efficacy in cells that did not secrete HRG, such as MCF-7 cells overexpressing a structural mutated HRG isoform. Therefore, trastuzumab-induced REC, in the absence of Her-2 overexpression, occurs through the kinase activity of Her-2/3. Interestingly, HRG expression in tumor biopsies from invasive breast carcinomas (n = 189) revealed that, whereas the minority (12%) of Her-2 positive tumors (n = 60; 32%) demonstrated Her-2 phosphorylation, the majority (67%) of HRG-overexpressing and Her-2 tumors (n = 57; 30%) were in active Her-2 status. CONCLUSION: We demonstrate that assessment of HRG expression and Her-2 activation define a particular breast cancer patient population for which trastuzumab plus CDDP or taxol are extremely efficient without Her-2 overexpression.

Heregulin-triggered Her-2/neu signaling enhances nuclear accumulation of p21WAF1/CIP1 and protects breast cancer cells from cisplatin-induced genotoxic damage.

Elevated levels of p21WAF1/CIP1, an important mediator of DNA repair, have been observed in various aggressive tumors as well as linked to chemoresistance. We examined whether heregulin (HRG), a member of the EGF-like growth factor family closely related to breast cancer tumorigenesis and metastasis, modulates p21WAF1/CIP1 expression and cellular localization. We used a model system that consisted of MCF-7 cells and MCF-7 cells engineered to overexpress the full-length cDNA of the human HRG gene (MCF-7/HRG). MCF-7/HRG cells demonstrate constitutive hyperactivation of Her-2/neu receptor as well as activation of down-stream PI-3'K/AKT and MAPK signaling cascades. Immunoblotting analyses showed that MCF-7/HRG cells significantly up-regulate p21WAF1/CIP1 expression relative to control MCF-7/pBABE cells, while a strong nuclear accumulation of p21WAF1/CIP1 in MCF-7/HRG cells was revealed by immunofluorescence microscopy studies. Protein degradation analyses demonstrated that the half-life of p21WAF1/CIP1 protein was increased from approximately 35 min in control MCF-7/pBABE cells to >/=3 h in MCF-7/HRG cells. Pharmacological inactivation of the PI-3'K/AKT and MAPK completely prevented HRG-induced accumulation of p21WAF1/CIP1. A structural deletion mutant of HRG (HRG-M4) lacking the N-terminus sequence and the cytoplasmic-transmembrane region of HRG was generated to investigate whether secretion of HRG and transactivation of Her-2/neu actively contributed to HRG-regulated p21WAF1/CIP1 expression and cellular localization. MCF-7 cells engineered to overexpress HRG-M4 did not demonstrate either activation of Her-2/neu, PI-3'K/AKT, or MAPK. Remarkably, HRG-M4 overexpression completely abolished the ability of HRG to promote nuclear accumulation of p21WAF1/CIP1 and concomitantly enhanced the apoptotic effects of cisplatin towards breast cancer cells. This novel interplay between HRG and p21WAF1/CIP1 strongly suggests that one mechanism of HRG-regulated breast cancer cell proliferation, survival, and/or sensitivity to genotoxic damage is to stabilize and promote a nuclear accumulation of p21WAF1/CIP1.

A novel CYR61-triggered 'CYR61-alphavbeta3 integrin loop' regulates breast cancer cell survival and chemosensitivity through activation of ERK1/ERK2 MAPK signaling pathway.

The angiogenic inducer CYR61 is differentially overexpressed in breast cancer cells exhibiting high levels of Heregulin (HRG), a growth factor closely associated with a metastatic breast cancer phenotype. Here, we examined whether CYR61, independently of HRG, actively regulates breast cancer cell survival and chemosensitivity, and the pathways involved. Forced expression of CYR61 in HRG-negative MCF-7 cells notably upregulated the expression of its own integrin receptor alphavbeta3 (>200 times). Small peptidomimetic alphavbeta3 integrin antagonists dramatically decreased cell viability of CYR61-overexpressing MCF-7 cells, whereas control MCF-7/V remained insensitive. Mechanistically, functional blockade of alphavbeta3 specifically abolished CYR6-induced hyperactivation of ERK1/ERK2 MAPK, whereas the activation status of AKT did not decrease. Moreover, CYR61 overexpression rendered MCF-7 cells significantly resistant (>10-fold) to Taxol-induced cytotoxicity. Remarkably, alphavbeta3 inhibition converted the CYR61-induced Taxol-resistant phenotype into a hypersensitive one. Thus, the augmentation of Taxol-induced apoptotic cell death in the presence of alphavbeta3 antagonists demonstrated a strong synergism as verified by the terminal transferase-mediated dUTP nick-end labeling (TUNEL) assay and by flow cytometric analysis for DNA content. Indeed, functional blockade of alphavbeta3, similarly to the pharmacological MAPK inhibitor U0126, synergistically increased both the proportion of CYR61-overexpressing breast cancer cells in the G2 phase of the cell cycle and the appearance of sub-G1 hypodiploid (apoptotic) cells caused by Taxol. Strikingly, CYR61 overexpression impaired the accumulation of wild-type p53 following Taxol exposure, while inhibition of alphavbeta3 or ERK1/ERK2 MAPK signalings completely restored Taxol-induced upregulation of p53. Moreover, antisense downregulation of CYR61 expression abolished the anchorage-independent growth of breast cancer cells engineered to overexpress HRG, and significantly increased their sensitivity to Taxol. Our data provide evidence that CYR61 is sufficient to promote breast cancer cell proliferation, cell survival, and Taxol resistance through a alphavbeta3-activated ERK1/ERK2 MAPK signaling. The identification of a 'CYR61-alphavbeta3 autocrine loop' in the epithelial compartment of breast carcinoma strongly suggests that targeting alphavbeta3 may simultaneously prevent breast cancer angiogenesis, growth, and chemoresistance.

Pharmacological inhibition of fatty acid synthase (FAS): a novel therapeutic approach for breast cancer chemoprevention through its ability to suppress Her-2/neu (erbB-2) oncogene-induced malignant transformation.

We designed our experiments to evaluate whether fatty acid synthase (FAS), a lipogenic enzyme linked to tumor virulence in population studies of human cancer, is necessary for the malignant transformation induced by Her-2/neu (erbB-2) oncogene, which is overexpressed not only in invasive breast cancer but also in premalignant atypical duct proliferations and in ductal carcinoma in situ of the breast. To avoid the genetic complexities associated with established breast cancer cell lines, we employed NIH-3T3 mouse fibroblasts engineered to overexpress human Her-2/neu coding sequence. NIH-3T3/Her-2 cells demonstrated a significant upregulation of FAS protein expression, which was dependent on the upstream activation of mitogen-activated protein kinase and phosphatidylinositol 3'-kinase/AKT pathways. Remarkably, pharmacological FAS blockade using the mycotoxin cerulenin or the novel small compound C75 completely suppressed the state of Her-2/neu-induced malignant transformation by inhibiting the ability of NIH-3T3/Her-2 cells to grow under either anchorage-independent (i.e., to form colonies in soft agar) or low-serum monolayer conditions. Moreover, NIH-3T3/Her-2 fibroblasts were up to three times more sensitive to chemical FAS inhibitors relative to untransformed controls as determined by MTT-based cell viability assays. In addition, pharmacological FAS blockade preferentially induced apoptotic cell death of NIH-3T3/Her-2 fibroblasts, as determined by an ELISA for histone-associated DNA fragments and by the terminal deoxynucleotidyltransferase (TdT)-mediated nick end labeling assay (TUNEL). Interestingly, the degree of Her-2/neu oncogene expression in a panel of breast cancer cell lines was predictive of sensitivity to chemical FAS inhibitors-induced cytotoxicity, while low-FAS expressing and chemical FAS inhibitors-resistant MDA-MB-231 breast cancer cells became hypersensitive to FAS blockade when they were engineered to overexpress Her-2/neu. Our observations strongly suggest that inhibition of FAS activity may provide a new molecular avenue for chemotherapeutic prevention and/or treatment of Her-2/neu-related breast carcinomas.

Inhibition of fatty acid synthase (FAS) suppresses HER2/neu (erbB-2) oncogene overexpression in cancer cells.

Fatty acid synthase (FAS) activity is a potential therapeutic target to treat cancer and obesity. Here, we have identified a molecular link between FAS and HER2 (erbB-2) oncogene, a marker for poor prognosis that is overexpressed in 30% of breast and ovarian cancers. Pharmacological FAS inhibitors cerulenin and C75 were found to suppress p185(HER2) oncoprotein expression and tyrosine-kinase activity in breast and ovarian HER2 overexpressors. Similarly, p185(HER2) expression was dramatically down-regulated when FAS gene expression was silenced by using the highly sequence-specific mechanism of RNA interference (RNAi). Pharmacological and RNAi-mediated silencing of FAS specifically down-regulated HER2 mRNA and, concomitantly, caused a prominent up-regulation of PEA3, a transcriptional repressor of HER2. A cytoplasmic redistribution of p185(HER2) was associated with marked morphological changes of FAS RNAi-transfected cells, whereas chemical inhibitors of FAS promoted a striking nuclear accumulation of p185(HER2). The simultaneous targeting of FAS and HER2 by chemical FAS inhibitors and the humanized antibody directed against p185(HER2) trastuzumab, respectively, was synergistically cytotoxic toward HER2 overexpressors. Similarly, concurrent RNAi-mediated silencing of FAS and HER2 genes synergistically stimulated apoptotic cell death in HER2 overexpressors. p185(HER2) was synergistically down-regulated after simultaneous inhibition of FAS and HER2 by either pharmacological inhibitors or small interfering RNA. These findings provide evidence of an active role of FAS in cancer evolution by specifically regulating oncogenic proteins closely related to malignant transformation, strongly suggesting that HER2 oncogene may act as the key molecular sensor of energy imbalance after the perturbation of tumor-associated FAS hyperactivity in cancer cells.