Identification of synergistic drug combinations using breast cancer patient-derived xenografts

Abstract

Compared with other breast cancer subtypes, triple-negative breast cancer (TNBC) is associated with relatively poor outcomes due to its metastatic propensity, frequent failure to respond to chemotherapy, and lack of alternative, targeted treatment options, despite decades of major research efforts. Our studies sought to identify promising targeted therapeutic candidates for TNBC through in vitro screening of 1,363 drugs in patient-derived xenograft (PDX) models. Using this approach, we generated a dataset that can be used to assess and compare responses of various breast cancer PDXs to many different drugs. Through a series of further drug screening assays and two-drug combination testing, we identified that the combination of afatinib (epidermal growth factor receptor (EGFR) inhibitor) and YM155 (inhibitor of baculoviral inhibitor of apoptosis repeat-containing 5 (BIRC5; survivin) expression) is synergistically cytotoxic across multiple models of basal-like TNBC and reduces PDX mammary tumor growth in vivo. We found that YM155 reduces EGFR expression in TNBC cells, shedding light on its potential mechanism of synergism with afatinib. Both EGFR and BIRC5 are highly expressed in basallike PDXs, cell lines, and patients, and high expression of both genes reduces metastasis-free survival, suggesting that co-targeting of these proteins holds promise for potential clinical success in TNBC. therefore suitable models for studying tumor biology and drug response, both in vivo and ex vivo/in vitro [22][23][24][25][26][27][28][29][30][31][32][33][34][35] . Using this approach, we have generated a dataset that can be used to quickly assess and compare responses of breast cancer PDXs of varying subtypes to many different drugs, most of which are approved by the U.S. Food and Drug Administration (FDA) for various cancer or non-cancer indications. From these data, we identified 176 drugs that were consistently effective across four basal-like TNBC PDXs, encompassing a wide variety of molecular targets and mechanisms of action. Several of these drugs have shown promising efficacy in TNBC and other solid tumors, however it is likely that incorporation into combination regimens is needed to maximize their efficacy and thus their likelihood of clinical success. Through a series of in vitro drug response assays, we selected four drugs to test in various two-drug combinations: carfilzomib (proteasome inhibitor), afatinib (epidermal growth factor receptor (EGFR) inhibitor), and YM155 (inhibitor of baculoviral inhibitor of apoptosis repeat-containing 5 (BIRC5; survivin) expression), along with carboplatin, a chemotherapeutic that is part of the current standard-of-care for TNBC and that we have previously tested in several PDXs 36 . Of the six drug combinations tested, we found that the combination of afatinib and YM155 was synergistically cytotoxic across four basal-like TNBC PDXs, and this drug combination significantly reduced PDX mammary tumor growth in vivo, without observable toxicity. Notably, the genes encoding the targets of ...

The metronomic combination of paclitaxel with cholinergic agonists inhibits triple negative breast tumor progression. Participation of M2 receptor subtype

“…Its expression and/or activity can be modulated by muscarinic receptors [38]. Several authors consider that the sole up-regulation of EGFR expression is a bad prognosis marker and an indicator of chemoresistance in TNBC patients or cell lines [39][40][41]. Our results demonstrated that the combination of PX plus carbachol or APE drastically reduced EGFR expression in tumor cells and this effect should be beneficial in the treatment of this type of tumor.…”

Methodological Advancements for Investigating Intra-tumoral Heterogeneity in Breast Cancer at the Bench and Bedside

“…For instance, combinatorial CRISPR-based screens may identify effective means with which to target ITH in breast tumor samples [ 151 ]. Large-scale drug screening platforms, such as those enabling high-throughput two-drug combination testing in PDX-derived cells [ 152 ], hold promise to identify combinations that are synergistically cytotoxic across multiple models. Use of cells that can be subsequently xenografted allows for in vivo validation of in vitro drug screen hits, further increasing the probability of clinical translation.…”

Laboratory Models for Investigating Breast Cancer Therapy Resistance and Metastasis

“…Interestingly, direct comparison of tamoxifen response in patients with their matched organoid cultures revealed congruent responses ( 14 ). Similarly, organoids have been derived from orthotopic PDX models, enabling high-throughput drug screening with panels of SOC and experimental compounds, providing novel avenues for preclinical drug testing ( 132 ) and synergistic combinations ( 133 ). Direct genomic and pharmacologic comparisons of organoids in vitro and tumors derived from orthotopic xenotransplantation into mice has revealed a high degree of concordance ( 16 ).…”