Mutant p53s generate pro-invasive niches by influencing exosome podocalyxin levels

Abstract

Mutant p53s (mutp53) increase cancer invasiveness by upregulating Rab-coupling protein (RCP) and diacylglycerol kinase-α (DGKα)-dependent endosomal recycling. Here we report that mutp53-expressing tumour cells produce exosomes that mediate intercellular transfer of mutp53’s invasive/migratory gain-of-function by increasing RCP-dependent integrin recycling in other tumour cells. This process depends on mutp53’s ability to control production of the sialomucin, podocalyxin, and activity of the Rab35 GTPase which interacts with podocalyxin to influence its sorting to exosomes. Exosomes from mutp53-expressing tumour cells also influence integrin trafficking in normal fibroblasts to promote deposition of a highly pro-invasive extracellular matrix (ECM), and quantitative second harmonic generation microscopy indicates that this ECM displays a characteristic orthogonal morphology. The lung ECM of mice possessing mutp53-driven pancreatic adenocarcinomas also displays increased orthogonal characteristics which precedes metastasis, indicating that mutp53 can influence the microenvironment in distant organs in a way that can support invasive growth.

Hypoxia alters the release and size distribution of extracellular vesicles in pancreatic cancer cells to support their adaptive survival

“…18,19,34 F I G U R E 6 HIF-1α mediates the effect of hypoxia on the release of extracellular vesicles (EVs) and their effect on hypoxic survival of pancreatic cancer cells. 23 Since a role of p53 has been reported in the development of EV, 35,36 it is likely that different p53 mutations and/or other genetic dissimilarities underlie the differential shedding of EVs by these two cell lines, which should be investigated in future studies. HIF-1α silencing was confirmed by immunoblotting.…”

CAF Subpopulations: A New Reservoir of Stromal Targets in Pancreatic Cancer

“…Abbreviations: a-SMA, alpha smooth muscle actin; BMDSC, bone marrow-derived stem cell; ECM, extracellular matrix; iCAF, inflammatory CAF; IL-6/8, interleukin 6/8; MSC, mesenchymal stem cell; myCAF, myofibroblastic CAF; PSC, pancreatic stellate cell; ROS, reactive oxygen species. produced an ECM with a similar stiffness to fibroblasts treated with p53null cancer cell-derived exosomes, but this ECM was significantly less adhesive [53]. These weaker cancer cell-matrix interactions allowed cancer cells to migrate and invade more readily over the ECM produced by p53muteducated fibroblasts compared with their p53null counterparts.…”

“…In line with this, Wö rmann and colleagues found that loss of tumour suppressor gene p53 function in PDAC tumour cells resulted in a more fibrotic stroma compared with wild-type p53 controls, which was conducive to tumour growth via activation of the Janus kinase 2-signal transducer and activator of transcription 3 (JAK2-STAT3) signalling pathway in cancer cells [52]. Furthermore, in a PDAC GEMM, pancreatic cancer cells with a gain-of-function (GoF) mutant p53 (p53mut) genotype were found to induce fibroblast activation via altered exosomal secretion of podocalyxin (PODXL), a highly sialylated glycoprotein, compared with the exosomes from p53null (p53null) cancer cells [53]. This p53mut-specific exosome signature also altered integrin signalling and increased ECM deposition by normal fibroblasts, pushing them towards a pro-invasive CAF-like phenotype [53].…”

“…Furthermore, in a PDAC GEMM, pancreatic cancer cells with a gain-of-function (GoF) mutant p53 (p53mut) genotype were found to induce fibroblast activation via altered exosomal secretion of podocalyxin (PODXL), a highly sialylated glycoprotein, compared with the exosomes from p53null (p53null) cancer cells [53]. This p53mut-specific exosome signature also altered integrin signalling and increased ECM deposition by normal fibroblasts, pushing them towards a pro-invasive CAF-like phenotype [53]. The fibroblasts that were exposed to p53mut cancer cell-derived exosomes (A) CAFs can originate from several different cell types and, therefore, exhibit a range of activation states that can be further stimulated to alter cancer development.…”

“…These weaker cancer cell-matrix interactions allowed cancer cells to migrate and invade more readily over the ECM produced by p53muteducated fibroblasts compared with their p53null counterparts. In addition, it was shown that exosomal PODXL released by p53mut cancer cells also significantly altered the ECM architecture of lung parenchyma in mice to be more amenable to metastatic colonization [53].…”