Systematic identification of signaling pathways with potential to confer anticancer drug resistance

Abstract

Cancer cells can activate diverse signaling pathways to evade the cytotoxic action of drugs. We created and screened a library of barcoded pathway-activating mutant cDNAs to identify those that enhanced the survival of cancer cells in the presence of 13 clinically relevant, targeted therapies. We found that activation of the RAS– MAPK (mitogen-activated protein kinase), Notch1, PI3K (phosphoinositide 3-kinase)–mTOR (mechanistic target of rapamycin), and ER (estrogen receptor) signaling pathways often conferred resistance to this selection of drugs. Activation of the Notch1 pathway promoted acquired resistance to tamoxifen (an ER-targeted therapy) in serially-passaged breast cancer xenografts in mice, and treating mice with a γ-secretase inhibitor to inhibit Notch signaling restored tamoxifen sensitivity. Markers of Notch1 activity in tumor tissue correlated with resistance to tamoxifen in breast cancer patients. Similarly, activation of Notch1 signaling promoted acquired resistance to MAPK inhibitors in BRAFV600E melanoma cells in culture, and the abundance of Notch1 pathway markers were increased in tumors from a subset of melanoma patients. Thus, Notch1 signaling may be a therapeutic target in some drug-resistant breast cancers and melanomas. Additionally, multiple resistance pathways were activated in melanoma cell lines with intrinsic resistance to MAPK inhibitors, and simultaneous inhibition of these pathways synergistically induced drug sensitivity. These data illustrate the potential for systematic identification of the signaling pathways controlling drug resistance that could inform clinical strategies and drug development for multiple types of cancer. This approach may also be used to advance clinical options in other disease contexts.

Notch promotes recurrence of dormant tumor cells following HER2/neu-targeted therapy

“…Consistent with this, pharmacologic inhibition of Notch signaling suppressed tumor recurrence when administered to mice bearing dormant MRD and reduced residual disease burden following HER2/neu blockade in a manner suggestive of a reduction in the number of residual tumor cells. Recent large-scale sequencing and screening approaches have identified recurrent Notch gene rearrangements (22), implicated Notch signaling in therapeutic resistance (28), and reinvigorated While it is currently unclear whether drugs targeting the Notch pathway will impair the growth of established primary or recurrent metastatic tumors, their use as adjuvant agents in the setting of dormant MRD -or in the neoadjuvant setting in combination with HER2/neu-targeted therapies -could enable the elimination of dormant residual cancer cells and, consequently, could enable the prevention of recurrence.…”

“…Recurrent gene rearrangements resulting in constitutive NOTCH1 activation have been identified in patients with estrogen receptor-negative (ER-negative) adenocarcinomas of the breast (22), and constitutive activation of Notch signaling in transgenic mice results in the formation of mammary tumors (23)(24)(25)(26)(27). Recent data also implicate Notch signaling in resistance to chemotherapy, hormone therapy and targeted therapy in breast cancer cell lines (28). Additionally, positive staining for the intracellular domain of NOTCH1 (NICD1) has been reported to be associated with an increased risk of recurrence in a series of 50 patients with ductal carcinoma in situ (29).…”

Overview of Research and Development for Anticancer Drugs

“…Current efforts to understand resistance often center on two different strategies. One approach is to model the development of resistance in vitro using sensitive cell line models that are exposed to a specific targeted therapy until resistance emerges [14]. A second approach focuses on the genetic analyses of resistant biopsies to identify new genetic anomalies that could be driving resistance [15].…”

Melanoma Therapeutic Strategies That Select Against Resistance by Exploiting MYC-Driven Evolutionary Convergence

“…Additionally, bypass mechanisms, including activation of the phosphoinositide-3-kinase (PI3K) pathway through mutations or altered expression of IGF-1R, PIK3CA, PTEN, and AKT, as well as through microenvironmental changes, can drive resistance (Alcala and Flaherty, 2012;Fedorenko and Smalley, 2015;Hugo et al, 2015;Paraiso et al, 2011;Rizos et al, 2014;Shi et al, 2014a;Shi et al, 2014b;Solit and Rosen, 2014;Villanueva et al, 2010). Similarly, bypass signaling through the Notch1 pathway via altered expression of Notch1 and other pathway members drives resistance in a third, distinct subset of patients (Martz et al, 2014). Importantly, these three pathways-ERK, PI3K and Notch1-have been shown to drive resistance to both single agent and combined BRAFi/MEKi, and together they appear to account for ~75% of acquired resistance cases while also playing important roles in intrinsic resistance Martz et al, 2014;Moriceau et al, 2015;Wagle et al, 2014).…”