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ProblemDevelopment of platinum resistance in ovarian cancer is mediated by both cancer cells and tumor microenvironment. Activation of epithelial-mesenchymal transition program in cancer cells may lead to enrichment for resistant clones. These processes can be affected by tumor-associated macrophages, a highly plastic population of cells that participate in tumor progression and response to treatment by shaping the microenvironment. We aimed to study how platinum resistance influences the crosstalk between macrophages and ovarian cancer cells., Method of studyUsing cisplatin-sensitive ovarian cancer cell line A2780, we developed and characterized cisplatin-resistant A2780Cis and cisplatin and doxorubicin co-resistant A2780Dox cell lines. Next, we set up an indirect coculture system with THP-1 cell line-derived M0-type-, M1-type- and M2-type-like polarized macrophages. We monitored the expression of genes associated with cellular stemness, multidrug resistance, and epithelial-mesenchymal transition in cancer cells, and expression profile of M1/M2 markers in macrophages., ResultsDevelopment of drug resistance in ovarian cancer cell lines was accompanied by increased migration, clonogenicity, and upregulated expression of transcription factors, associated with cellular stemness and epithelial-mesenchymal transition. Upon coculture, we noted that the most relevant changes in gene expression profile occurred in A2780 cells. Moreover, M0- and M1-type macrophages, but not M2-type macrophages, showed significant transcriptional alterations., ConclusionOur results provide the evidence for bidirectional interplay between cancer cells and macrophages. Independent of platinum resistance status, ovarian cancer cells polarize macrophages toward M2-like type, whereas macrophages induce epithelial-mesenchymal transition and stemness-related gene expression profile in cisplatin-sensitive, but not cisplatin-resistant cancer cells.

Summary Therapeutic targeting of tumor angiogenesis with VEGF inhibitors results in demonstrable, but transitory efficacy in certain human tumors and mouse models of cancer, limited by unconventional forms of adaptive/evasive resistance. In one such mouse model, potent angiogenesis inhibitors elicit compartmental reorganization of cancer cells around remaining blood vessels. The glucose and lactate transporters GLUT1 and MCT4 are induced in distal hypoxic cells in a HIF1α-dependent fashion, indicative of glycolysis. Tumor cells proximal to blood vessels instead express the lactate transporter MCT1, and p-S6, the latter reflecting mTOR signaling. Normoxic cancer cells import and metabolize lactate, resulting in upregulation of mTOR signaling via glutamine metabolism enhanced by lactate catabolism. Thus, metabolic symbiosis is established in the face of angiogenesis inhibition, whereby hypoxic cancer cells import glucose and export lactate, while normoxic cells import and catabolize lactate. mTOR signaling inhibition disrupts this metabolic symbiosis, associated with upregulation of the glucose transporter GLUT2., Graphical Abstract, Highlights • Angiogenesis inhibitors causing acute hypoxia elicit metabolic compartmentalization • Hypoxic cancer cells import and metabolize glucose, secreting lactate • Normoxic vessel-proximal cancer cells import and metabolize lactate, involving mTOR • Co-inhibiting mTOR disrupts the metabolic symbiosis, Allen et al. find that inhibitors of tumor angiogenesis that cause acute hypoxia elicit compartmentalization of cancer cells into symbiotic clusters. Hypoxic cancer cells metabolize glucose and secrete lactate; normoxic, vessel-proximal cancer cells import and metabolize the lactate in a process involving mTOR signaling. Co-inhibition of mTOR disrupts the symbiosis, in part by upregulating glucose transport in normoxic cells.

Summary Genetic linkage analysis previously suggested that GKAP, a scaffold protein of the N-methyl-D-aspartate receptor (NMDAR), was a potential modifier of invasion in a mouse model of pancreatic neuroendocrine tumor (PanNET). Here, we establish that GKAP governs invasive growth and treatment response to NMDAR inhibitors of PanNET via its pivotal role in regulating NMDAR pathway activity. Combining genetic knockdown of GKAP and pharmacological inhibition of NMDAR, we implicate as downstream effectors FMRP and HSF1, which along with GKAP demonstrably support invasiveness of PanNET and pancreatic ductal adenocarcinoma cancer cells. Furthermore, we distilled genome-wide expression profiles orchestrated by the NMDAR-GKAP signaling axis, identifying transcriptome signatures in tumors with low/inhibited NMDAR activity that significantly associate with favorable patient prognosis in several cancer types., Graphical Abstract, Highlights • GKAP governs invasive growth of pancreatic cancers via NMDAR signaling • HSF1 and FMRP are downstream effectors of the NMDAR-GKAP axis • A multigene signature of low/inhibited NMDAR-GKAP pathway activity is reported • A low-NMDAR-GKAP signature predicts better survival for various human cancers, Li et al. show that GKAP, a scaffold protein of NMDAR, and its downstream effectors FMRP and HSF1 play important roles in the invasive growth of pancreatic tumors. In several cancer types, low NMDAR activity, based on a transcriptomic signature, associates with favorable patient prognosis.