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Background: Cancer-associated fibroblasts (CAFs) coordinate the malignancy of cancer cells via secretory materials. Reprogrammed lipid metabolism and signaling play critical roles in cancer biology. Oleic acid (OA) serves as a source of energy under glucose-deficient conditions, but its function in cancer progression remains unclear. The present study investigated that CAFs in xenografted tumors had higher amounts of fatty acids, particularly OA, compared to normal fibroblasts, and promoted the cancer cell stemness in lung adenocarcinoma cells under glucose-deficient condition. Methods: Xenografts were established in immunodeficient mice by injection of NCI-H460 (H460) cells. Lipids and fatty acids were evaluated using the BODIPY staining and fatty-acid methyl esters analysis. The expression levels of markers for lipid metabolism and cancer stemness were determined by western blot, flow cytometry, and real-time PCR. Cancer cell subclones against stearoyl-CoA desaturase (SCD) were produced by lentiviral vector and CRISPR/cas9 systems. The expression of SCD was examined immunochemically in human adenocarcinoma tissues, and its clinical relevance to survival rate in lung adenocarcinoma patients was assessed by Kaplan–Meier analysis. Results: Transferred CAF-derived OA through lipid transporter upregulated SCD in cancer cells under glucose-deficient conditions, resulting in enhanced lipid metabolism and autophagosome maturation. By OA treatment under glucose deficient condition, cancer cell stemness was significantly enhanced through sequential activation of SCD, F-actin polymerization and nuclear translocation of yes-associated protein. These findings were confirmed by experiments using chemical inhibitors, SCD-overexpressing cells and SCD-knockout (KO) cells. When xenografted, SCD-overexpressing cells produced larger tumors compared with parental cells, while SCD-KO cells generated much smaller tumors. Analysis of tumor tissue microarray from lung adenocarcinoma patients revealed that SCD expression was the marker for poor prognosis involving tumor grade, clinical stage and survival rate. Conclusion: Our data indicate that CAFs-derived OA activated lipid metabolism in lung adenocarcinoma cells under glucose-deficient conditions, subsequently enhancing stemness and progression toward malignancy. [ABSTRACT FROM AUTHOR]

Cancer-associated fibroblasts (CAFs) are an abundant component of the tumor microenvironment and have distinct features from normal fibroblasts (NFs). However, the discriminative nature of heterogeneous CAFs under glucose starvation remains unknown. In this study, we investigated the changes in the mitochondrial calcium concentration and relevant intracellular machinery in CAFs under glucose-deficient conditions. Xenografted tumor masses were dissected into multiple pieces and subjected to the CAF isolation using magnetically activated cell sorting (MACS). NFs were separated from the normal lung and skin. Under glucose starvation, CAFs from the tumor mass exhibited heterogeneity in cell proliferation, ATP production and calcium concentration. Compared to NFs, mitochondrial calcium concentration was significantly higher in glucose-starved CAFs with upregulation of mitochondrial calcium uniporter (MCU) that led to enhancement of ATP production and cell growth. Intriguingly, treatment of glucose-starved CAFs with oligomycin increased apoptosis by disrupted calcium homeostasis following overactivation of the mPTP. Moreover, oligomycin-induced apoptosis was mitigated by calcium chelation. This study demonstrated that the discriminative calcium influx to mitochondria through MCU coordinated cell growth and apoptosis in glucose-starved CAFs but not in NFs. • CAFs from a tumor mass are heterogeneous under the glucose deficient condition. • CAFs survive under glucose deficient condition by activation of TGF-β and calcium. • Calcium influx to mitochondria is critical for survival of glucose-deficient CAFs. • MCU in CAFs could be a feasible target for the development of anticancer drugs. [ABSTRACT FROM AUTHOR]