Metastatic triple-negative breast cancer: Established and emerging treatments

Inhibition of the mitochondrial protein Opa1 curtails breast cancer growth

BACKGROUND

Mitochondrial fusion and fission proteins have been nominated as druggable targets in cancer. Whether their inhibition is efficacious in triple negative breast cancer (TNBC) that almost invariably develops chemoresistance is unknown.

METHODS

We used a combination of bioinformatics analyses of cancer genomic databases, genetic and pharmacological Optic Atrophy 1 (OPA1) inhibition, mitochondrial function and morphology measurements, micro-RNA (miRNA) profiling and formal epistatic analyses to address the role of OPA1 in TNBC proliferation, migration, and invasion in vitro and in vivo.

RESULTS

We identified a signature of OPA1 upregulation in breast cancer that correlates with worse prognosis. Accordingly, OPA1 inhibition could reduce breast cancer cells proliferation, migration, and invasion in vitro and in vivo. Mechanistically, while OPA1 silencing did not reduce mitochondrial respiration, it increased levels of miRNAs of the 148/152 family known to inhibit tumor growth and invasiveness. Indeed, these miRNAs were epistatic to OPA1 in the regulation of TNBC cells growth and invasiveness.

CONCLUSIONS

Our data show that targeted inhibition of the mitochondrial fusion protein OPA1 curtails TNBC growth and nominate OPA1 as a druggable target in TNBC.

Excellent effects and possible mechanisms of action of a new antibody-drug conjugate against EGFR-positive triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is the most aggressive subtype and occurs in approximately 15-20% of diagnosed breast cancers. TNBC is characterized by its highly metastatic and recurrent features, as well as a lack of specific targets and targeted therapeutics. Epidermal growth factor receptor (EGFR) is highly expressed in a variety of tumors, especially in TNBC. LR004-VC-MMAE is a new EGFR-targeting antibody-drug conjugate produced by our laboratory. This study aimed to evaluate its antitumor activities against EGFR-positive TNBC and further studied its possible mechanism of antitumor action.

METHODS

LR004-VC-MMAE was prepared by coupling a cytotoxic payload (MMAE) to an anti-EGFR antibody (LR004) via a linker, and the drug-to-antibody ratio (DAR) was analyzed by HIC-HPLC. The gene expression of EGFR in a series of breast cancer cell lines was assessed using a publicly available microarray dataset (GSE41313) and Western blotting. MDA-MB-468 and MDA-MB-231 cells were treated with LR004-VC-MMAE (0, 0.0066, 0.066, 0.66, 6.6 nmol/L), and the inhibitory effects of LR004-VC-MMAE on cell proliferation were examined by CCK-8 and colony formation. The migration and invasion capacity of MDA-MB-468 and MDA-MB-231 cells were tested at different LR004-VC-MMAE concentrations (2.5 and 5 nmol/L) with wound healing and Transwell invasion assays. Flow cytometric analysis and tumorsphere-forming assays were used to detect the killing effects of LR004-VC-MMAE on cancer stem cells in MDA-MB-468 and MDA-MB-231 cells. The mouse xenograft models were also used to evaluate the antitumor efficacy of LR004-VC-MMAE in vivo. Briefly, BALB/c nude mice were subcutaneously inoculated with MDA-MB-468 or MDA-MB-231 cells. Then they were randomly divided into 4 groups (n = 6 per group) and treated with PBS, naked LR004 (10 mg/kg), LR004-VC-MMAE (10 mg/kg), or doxorubicin, respectively. Tumor sizes and the body weights of mice were measured every 4 days. The effects of LR004-VC-MMAE on apoptosis and cell cycle distribution were analyzed by flow cytometry. Western blotting was used to detect the effects of LR004-VC-MMAE on EGFR, ERK, MEK phosphorylation and tumor stemness marker gene expression.

RESULTS

LR004-VC-MMAE with a DAR of 4.02 were obtained. The expression of EGFR was found to be significantly higher in TNBC cells compared with non-TNBC cells (P < 0.01). LR004-VC-MMAE inhibited the proliferation of EGFR-positive TNBC cells, and the IC50 values of MDA-MB-468 and MDA-MB-231 cells treated with LR004-VC-MMAE for 72 h were (0.13 ± 0.02) nmol/L and (0.66 ± 0.06) nmol/L, respectively, which were significantly lower than that of cells treated with MMAE [(3.20 ± 0.60) nmol/L, P < 0.01, and (6.60 ± 0.50) nmol/L, P < 0.001]. LR004-VC-MMAE effectively inhibited migration and invasion of MDA-MB-468 and MDA-MB-231 cells. Moreover, LR004-VC-MMAE also killed tumor stem cells in EGFR-positive TNBC cells and impaired their tumorsphere-forming ability. In TNBC xenograft models, LR004-VC-MMAE at 10 mg/kg significantly suppressed tumor growth and achieved complete tumor regression on day 36. Surprisingly, tumor recurrence was not observed until the end of the experiment on day 52. In a mechanistic study, we found that LR004-VC-MMAE significantly induced cell apoptosis and cell cycle arrest at G2/M phase in MDA-MB-468 [(34 ± 5)% vs. (12 ± 2)%, P < 0.001] and MDA-MB-231 [(27 ± 4)% vs. (18 ± 3)%, P < 0.01] cells. LR004-VC-MMAE also inhibited the activation of EGFR signaling and the expression of cancer stemness marker genes such as Oct4, Sox2, KLF4 and EpCAM.

CONCLUSIONS

LR004-VC-MMAE showed effective antitumor activity by inhibiting the activation of EGFR signaling and the expression of cancer stemness marker genes. It might be a promising therapeutic candidate and provides a potential therapeutic avenue for the treatment of EGFR-positive TNBC.

Sacituzumab Govitecan for Metastatic Triple-Negative Breast Cancer: Clinical Overview and Management of Potential Toxicities

Patients with metastatic triple-negative breast cancer have a poor prognosis. Sacituzumab govitecan (IMMU-132) is an antibody-drug conjugate that contains the irinotecan active metabolite, SN-38, linked to a humanized monoclonal antibody targeting trophoblast cell surface antigen 2, which is overexpressed in many solid tumors. In a basket design phase I/II study, sacituzumab govitecan demonstrated promising single-agent therapeutic activity in multiple cancer cohorts, leading to accelerated approval by the U.S. Food and Drug Administration of sacituzumab govitecan-hziy (TRODELVY) for the treatment of patients with metastatic triple-negative breast cancer who had received at least two prior therapies in the metastatic setting. Recently, results of the phase III trial, ASCENT, were confirmatory. There is limited available information on the adverse event management with sacituzumab govitecan needed to maximize the dose and duration of effective therapy while maintaining patient quality of life. This review summarizes the clinical development and the practical management of patients receiving sacituzumab govitecan. Sacituzumab govitecan has a well-defined and manageable toxicity profile, and rapid recognition and appropriate early and proactive management will allow clinicians to optimize sacituzumab govitecan treatment for patients. IMPLICATIONS FOR PRACTICE: Sacituzumab govitecan (TRODELVY) is a novel antibody-drug conjugate composed of the active metabolite of irinotecan (SN-38) conjugated to a monoclonal antibody targeting trophoblast cell surface antigen 2, an epithelial cell surface antigen overexpressed in many cancers. Because of the rapid approval of sacituzumab govitecan, there is limited available information on adverse event (AE) management with this agent. As such, this article reviews the clinical development of the drug, the AE profile, and provides recommendations regarding AE management to help optimize therapy with sacituzumab govitecan.

Case Report of a Breast Mass with Three Types of Malignant Tumors-Squamous Cell Carcinoma, Invasive Ductal Carcinoma, and Breast Sarcoma

Breast malignancy comprises malignant tumors originating from epithelial tissue and breast sarcoma arising from mesodermal tissues. Despite heterogeneity in tumors, most malignant tumors of the breast are composed of a single type of tumor. Here, we report a patient with breast tumor consisting of three different types of malignancies—squamous cell carcinoma, invasive ductal carcinoma, and high-grade breast sarcoma.

Utilizing Data Visualization to Identify Survival and Treatment Differences Between Women With De Novo and Recurrent Metastatic Breast Cancer

INTRODUCTION

De novo stage IV metastatic breast cancer (MBC) and recurrent MBC are considered the same when determining guideline-based care, but differences in treatment patterns exist. Data visualization can be used to understand these differences and optimize treatment delivery.

PATIENTS AND METHODS

This retrospective study evaluated treatment patterns for de novo and recurrent MBC using the American Society of Clinical Oncology's CancerLinQ Discovery database. Spatiotemporal graphics depicting treatment data were generated for MBC subtype and stratified by de novo and recurrent MBC. Descriptive statistics for categorical and continuous variables were calculated.

RESULTS

We identified 1668 patients diagnosed and treated for MBC: 391 patients with HER2⁺ MBC, 767 patients with HR⁺/HER2- MBC, and 510 patients with triple-negative MBC. Median survival from MBC diagnosis for patients with de novo MBC and recurrent MBC was 1.4 years (interquartile range, 0.6-3.0) and 1.8 years (interquartile range, 0.7-4.5), respectively. Both patients with de novo and recurrent HER2⁺ MBC were often treated with continuous HER2-targeted therapy. Patients with de novo HR⁺/HER2- MBC often received chemotherapy followed by hormone therapy. This contrasted with treatment trends observed among patients with recurrent HR⁺/HER2- MBC who, after receiving chemotherapy, seldom went on to receive hormone therapy. Patients diagnosed with triple-negative MBC displayed less heterogeneous treatment trends.

CONCLUSION

There are observable differences in survival and practice patterns between de novo and recurrent MBC. Visualization techniques are effective in assessing large databases and could give researchers and clinicians a clearer understanding of how survival differs by disease subtype, diagnosis status, and practice patterns.

Management of brain metastases according to molecular subtypes

The incidence of brain metastases has markedly increased in the past 20 years owing to progress in the treatment of malignant solid tumours, earlier diagnosis by MRI and an ageing population. Although local therapies remain the mainstay of treatment for many patients with brain metastases, a growing number of systemic options are now available and/or are under active investigation. HER2-targeted therapies (lapatinib, neratinib, tucatinib and trastuzumab emtansine), alone or in combination, yield a number of intracranial responses in patients with HER2-positive breast cancer brain metastases. New inhibitors are being investigated in brain metastases from ER-positive or triple-negative breast cancer. Several generations of EGFR and ALK inhibitors have shown activity on brain metastases from EGFR and ALK mutant non-small-cell lung cancer. Immune-checkpoint inhibitors (ICIs) hold promise in patients with non-small-cell lung cancer without druggable mutations and in patients with triple-negative breast cancer. The survival of patients with brain metastases from melanoma has substantially improved after the advent of BRAF inhibitors and ICIs (ipilimumab, nivolumab and pembrolizumab). The combination of targeted agents or ICIs with stereotactic radiosurgery could further improve the response rates and survival but the risk of radiation necrosis should be monitored. Advanced neuroimaging and liquid biopsy will hopefully improve response evaluation.