A histone methylation-MAPK signaling axis drives durable epithelial-mesenchymal transition in hypoxic pancreas cancer

Abstract

Here, we show that hypoxia drives especially long-lasting epithelial-mesenchymal transition (EMT) in pancreatic ductal adenocarcinoma (PDAC) primarily through a positive-feedback histone methylation-MAPK signaling axis. We find that neoplastic PDAC cells preferentially undergo EMT in hypoxic tumor regions in multiple model systems and that hypoxia drives a cell-autonomous EMT in PDAC cells which, unlike EMT in response to growth factors, can last for weeks. We further demonstrate that hypoxia reduces histone demethylase KDM2A activity, suppresses PP2 family phosphatase expression, and activates MAPKs to post-translationally stabilize histone methyltransferase NSD2, leading to an H3K36me2-dependent EMT in which hypoxia-inducible factors play only a supporting role. This mechanism can be antagonized in vivo by combinations of MAPK inhibitors that may be effective in multi-drug therapies designed to target EMT.

Single-cell RNA sequencing reveals microenvironment context-specific routes for epithelial-mesenchymal transition in pancreas cancer cells

“…Additionally, to account for the hypoxia-specific enrichment of AXL, studies have found that HIF-1⍺ and HIF-2⍺ directly promote AXL expression, which promotes SRC activity (33). We have previously established a role for SRC-dependent MAPK/ERK-signaling in regulating hypoxiamediated EMT (3), which unifies the present study and previous findings on FAT1 and AXL to provide a mechanism for hypoxia-driven EMT in PDAC.…”

“…HPAF-II cells were used because they are baseline epithelial and an established model for welldifferentiated PDAC (23). As we have observed previously (3), the extent of mesenchymal transition differed between growth factors and hypoxia as EMT drivers, with hypoxia promoting vimentin expression in only a minority of cells and growth factors causing most cells to express abundant vimentin (Figure 1A). Thus, both conditions produced a heterogeneous EMT among cells but to different degrees.…”

“…In pancreatic ductal adenocarcinoma (PDAC), an especially aggressive tumor subtype exists that is enriched in mesenchymal characteristics. The mesenchymal phenotype is associated with decreased survival and increased resistance to therapy relative to other subtypes (1)(2)(3)(4) and correlates with gene signatures for ductal cell epithelial-mesenchymal transition (EMT) (3). EMT occurs in response to varied initiating factors in the PDAC tumor microenvironment, including receptor ligands such as transforming growth factor beta (TGFβ), hepatocyte growth factor (HGF), and epidermal growth factor (5)(6)(7), and the low oxygen tension (hypoxia) resulting from PDAC tumor hypovascularity (3,(8)(9)(10).…”

“…EMT occurs heterogeneously in PDAC tumors and cell populations (11)(12)(13). Even in cell culture conditions, where spatial variation in extrinsic EMT-driving factors is minimal, phenotypic heterogeneity is observed, and the degree of heterogeneity depends on cell background and mode of EMT induction (3). Heterogeneity is also affected by the durability of the transition, which is greater in response to hypoxia than growth factors (3).…”

“…Even in cell culture conditions, where spatial variation in extrinsic EMT-driving factors is minimal, phenotypic heterogeneity is observed, and the degree of heterogeneity depends on cell background and mode of EMT induction (3). Heterogeneity is also affected by the durability of the transition, which is greater in response to hypoxia than growth factors (3). EMT heterogeneity endows differential chemoresistance to a subset of cells within tumors (12) and, as with any form of cell-to-cell heterogeneity, creates challenges for understanding the signaling or transcriptional processes that govern the phenotype (14).…”