Tumour cells secrete exosomes that are involved in the remodelling of the tumour-stromal environment and promoting malignancy. The mechanisms governing tumour exosome release, however, remain incompletely understood. Here we show that tumour cell exosomes secretion is controlled by pyruvate kinase type M2 (PKM2), which is upregulated and phosphorylated in tumours. During exosome secretion, phosphorylated PKM2 serves as a protein kinase to phosphorylate synaptosome-associated protein 23 (SNAP-23), which in turn enables the formation of the SNARE complex to allow exosomes release. Direct phosphorylation assay and mass spectrometry confirm that PKM2 phosphorylates SNAP-23 at Ser95. Ectopic expression of non-phosphorylated SNAP-23 mutant (Ser95→Ala95) significantly reduces PKM2-mediated exosomes release whereas expression of selective phosphomimetic SNAP-23 mutants (Ser95→Glu95 but not Ser20→Glu20) rescues the impaired exosomes release induced by PKM2 knockdown. Our findings reveal a non-metabolic function of PKM2, an enzyme associated with tumour cell reliance on aerobic glycolysis, in promoting tumour cell exosome release.

Normal fibroblasts surrounding tumor cells play a crucial role in cancer progression through formation of the tumor microenvironment. Because factors secreted from normal fibroblasts can modulate the tumor microenvironment, it is necessary to identify key factors associated with regulation of secreted factors and to investigate the molecular mechanisms contributing to the tumor microenvironment formation process. In this study, we found that radiation induced the expression and K63-linkage poly-ubiquitination of TRAF4 in normal lung fibroblasts. The K63-linkage poly-ubiquitinated TRAF4 formed complexes with NOX2 or NOX4 by mediating phosphorylated p47-phox in normal lung fibroblasts. Moreover, we showed that TRAF4 stabilized NOX complexes by decreasing lysosomal degradation of NOX2 and NOX4 after irradiation. NOX complexes increased endosomal ROS levels that were permeable into cytoplasm, leading to NF-κB-mediated ICAM1 up-regulation. Soluble ICAM1 was subsequently secreted into conditioned media of radiation-activated normal lung fibroblasts. The conditioned media from irradiated normal fibroblasts enhanced proliferation and epithelial-mesenchymal transition of non-small cell lung cancer cells both in vitro and in vivo. These results demonstrate that TRAF4 in irradiated fibroblasts is positively associated with aggressiveness of adjacent cancer cells by altering the tumor microenvironment. Thus, we suggest that regulation of TRAF4 might be a promising strategy for cancer therapy.

Secreted Protein Acidic and Rich in Cysteine (SPARC)-related modular calcium-binding protein-2 (SMOC2), a secreted matricellular protein, is reported to be involved in various processes related to cancer progression such as regulating the cell cycle, angiogenesis, and invasion. However, its expression and prognostic significance in papillary thyroid carcinomas (PTCs) remains unknown. Using immunohistochemistry, we evaluated the expression profile of SMOC2 and its prognostic value in a large cohort of PTCs. Real time-PCR analysis with fresh-frozen tissues showed that SMOC2 mRNA expression in PTCs was substantially lower than the expression in matched non-cancerous thyroid tissues, consistent with the results from thyroid cancer cell lines. Immunohistochemical analysis demonstrated that SMOC2 was normally present in thyroid follicular epithelial cells and the expression level was maintained in nodular hyperplasia. However, SMOC2 expression was significantly lower in lymphocytic thyroiditis and follicular tumors including follicular adenomas and carcinomas. In particular, 38% of PTCs exhibited a complete loss of SMOC2 expression, which was associated with the presence of BRAF (V600E) mutation. Moreover, SMOC2 further declined during lymph node metastasis in PTCs. DNA methylation chip analysis revealed one hypermethylated CpG site in the promoter region of SMOC2 gene, suggesting an epigenetic regulation of SMOC2 in PTCs. Remarkably SMOC2 positivity was associated with improved recurrence-free survival along with female sex, tumor size, and the N stage. However, SMOC2 was not identified as an independent prognostic marker in multivariate analyses. Taken together, SMOC2 expression is significantly down-regulated in PTCs and SMOC2 positivity is closely associated with better clinical outcomes, suggesting that SMOC2 can be a prognostic marker in PTC patients.

Circular RNAs (circRNAs) are known to act as key regulators in a variety of malignancies. However, the role of circRNAs in cervical cancer (CCa) remains largely unknown. Herein, we demonstrated that a circRNA derived from the TADA2A gene (hsa_circ_0043280) was significantly downregulated in CCa and that this reduction in expression was correlated with a poor prognosis. Furthermore, our results demonstrated that hsa_circ_0043280 functions as a tumor suppressor to inhibit tumor growth and metastasis in CCa. Mechanistically, hsa_circ_0043280 competitively sponges miR-203a-3p and prevents miR-203a-3p from reducing the levels of PAQR3. Collectively, our results demonstrate that hsa_circ_0043280 plays a pivotal role in the development and metastasis of CCa, thus suggesting that hsa_circ_0043280 has significant potential as a prognostic biomarker and a therapeutic target for CCa.

Hepatocellular carcinoma (HCC) is frequently characterized by metabolic and immune remodeling in the tumor microenvironment. We previously discovered that liver-specific deletion of fructose-1, 6-bisphosphatase 1 (FBP1), a gluconeogenic enzyme ubiquitously suppressed in HCC tissues, promotes liver tumorigenesis and induces metabolic and immune perturbations closely resembling human HCC. However, the underlying mechanisms remain incompletely understood. Here, we reported that FBP1-deficient livers exhibit diminished amounts of natural killer (NK) cells and accelerated tumorigenesis. Using the diethylnitrosamine-induced HCC mouse model, we analyzed potential changes in the immune cell populations purified from control and FBP1-depleted livers and found that NK cells were strongly suppressed. Mechanistically, FBP1 attenuation in hepatocytes derepresses an zeste homolog 2 (EZH2)-dependent transcriptional program to inhibit PKLR expression. This leads to reduced levels of PKLR cargo proteins sorted into hepatocyte-derived extracellular vesicles (EVs), dampened activity of EV-targeted NK cells, and accelerated liver tumorigenesis. Our study demonstrated that hepatic FBP1 depletion promotes HCC-associated immune remodeling, partly through the transfer of hepatocyte-secreted, PKLR-attenuated EVs to NK cells.

Lymph node (LN) metastasis is one of the most malignant clinical features in patients with cervical cancer (CCa). Understanding the mechanism of lymph node metastasis will provide treatment strategies for patients with CCa. Circular RNAs (circRNA) play a critical role in the development of human cancers. However, the role and mechanism of circRNAs in lymph node metastasis remain largely unknown. Here, it is reported that loss expression of circRNA circVPRBP was closely associated with LN metastasis and poor survival of CCa patients. In vitro and in vivo assays showed that circVPRBP overexpression notably inhibited lymphangiogenesis and LN metastasis, whereas RfxCas13d mediated silencing of circVPRBP promoted lymphangiogenesis and the ability of the cervical cancer cells to metastasize to the LNs. Mechanistically, circVPRBP could bind to RACK1 and shield the S122 O-GlcNAcylation site to promote RACK1 degradation, resulting in inhibition of Galectin-1 mediated lymphangiogenesis and LN metastasis in CCa. Taken together, the results demonstrate that circVPRBP is a potential prognostic biomarker and a novel therapeutic target for LN metastasis in CCa patients.

Amino acid metabolism has been actively investigated as a potential target for antitumor therapy, but how it may alter the response to genotoxic chemotherapy remains largely unknown. Here, we report that the depletion of fumarylacetoacetate hydrolase (FAH), an enzyme that catalyzes the final step of tyrosine catabolism, reduced chemosensitivity in epithelial ovarian cancer (EOC). The expression level of FAH correlated significantly with chemotherapy efficacy in patients with EOC. Mechanistically, under genotoxic chemotherapy, FAH is oxidized at Met308 and translocates to the nucleus, where FAH-mediated tyrosine catabolism predominantly supplies fumarate. FAH-produced fumarate binds directly to REV1, resulting in the suppression of translesion DNA synthesis (TLS) and improved chemosensitivity. Furthermore, in vivo tyrosine supplementation improves sensitivity to genotoxic chemotherapeutics and reduces the occurrence of therapy resistance. Our findings reveal a unique role for tyrosine-derived fumarate in the regulation of TLS and may be exploited to improve genotoxic chemotherapy through dietary tyrosine supplementation.