Microenvironment-Induced Non-sporadic Expression of the AXL and cKIT Receptors Are Related to Epithelial Plasticity and Drug Resistance

Abstract

The existence of rare cancer cells that sporadically acquire drug-tolerance through epigenetic mechanisms is proposed as one mechanism that drives cancer therapy failure. Here we provide evidence that specific microenvironments impose non-sporadic expression of proteins related to epithelial plasticity and drug resistance. Microarrays of robotically printed combinatorial microenvironments of known composition were used to make cell-based functional associations between microenvironments, which were design-inspired by normal and tumor-burdened breast tissues, and cell phenotypes. We hypothesized that specific combinations of microenvironment constituents non-sporadically impose the induction of the AXL and cKIT receptor tyrosine kinase proteins, which are known to be involved in epithelial plasticity and drug-tolerance, in an isogenic human mammary epithelial cell (HMEC) malignant progression series. Dimension reduction analysis reveals type I collagen as a dominant feature, inducing expression of both markers in pre-stasis finite lifespan HMECs, and transformed non-malignant and malignant immortal cell lines. Basement membrane-associated matrix proteins, laminin-111 and type IV collagen, suppress AXL and cKIT expression in pre-stasis and non-malignant cells. However, AXL and cKIT are not suppressed by laminin-111 in malignant cells. General linear models identified key factors, osteopontin, IL-8, and type VIα3 collagen, which significantly upregulated AXL and cKIT, as well as a plasticity-related gene expression program that is often observed in stem cells and in epithelial-to-mesenchymal-transition. These factors are co-located with AXL-expressing cells in situ in normal and breast cancer tissues, and associated with resistance to paclitaxel. A greater diversity of microenvironments induced AXL and cKIT expression consistent with plasticity and drug-tolerant phenotypes in tumorigenic cells compared to normal or immortal cells, suggesting a reduced perception of microenvironment specificity in malignant cells. Microenvironment-imposed reprogramming could explain why resistant cells are seemingly persistent and rapidly adaptable to multiple classes of drugs. These results support the notion that specific microenvironments drive drug-tolerant cellular phenotypes and suggest a novel interventional avenue for preventing acquired therapy resistance.

AXL Controls Directed Migration of Mesenchymal Triple-Negative Breast Cancer Cells

“…We also observed that AXL was mainly expressed by tumor cells in contact with the stroma. A recent study shows that AXL expression is higher in collagen-I rich microenvironment [75] suggesting that the extracellular matrix could have an impact in AXL expression. In breast tumors, Gas6 is highly expressed in pre-invasive lesions associated with increased infiltrating macrophages [76].…”

Gas6 is dispensable for pubertal mammary gland development

“…Since MaSCs with self-renewing properties and in vivo repopulating activity are also expressed in a subpopulation of basal cells, it is tempting to speculate that Axl may be a putative stem cell marker. Indeed, Axl has been suggested to be a cancer stem cell marker [27, 28], however it is unclear as to whether Axl is a true MaSC marker in the normal mammary gland.…”

Decoding cancer’s camouflage: epithelial-mesenchymal plasticity in resistance to immune checkpoint blockade

“…The tumor microenvironment is a key regulator of EMP, which may be induced by combinations of multiple microenvironmental factors including hypoxia, pH, ECM composition, tensile forces and the presence of soluble factors such as interferons, inflammatory cytokines and growth factors [61,65,66,86,[96][97][98] . Hypoxia occurs in most actively growing solid tumors and is an important EMT inducer.…”