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.
Hepatocellular carcinoma (HCC) generally possesses a high resistance to chemotherapy. Given that autophagy is an important factor promoting tumor chemoresistance and HCC express low level of miR-26, we aim to investigate the functional role of miR-26 in autophagy-mediated chemoresistance of HCC. We found that chemotherapeutic drug doxorubicin (Dox) induced autophagy but decreased the level of miR-26a/b in HCC cells. Activating autophagy using rapamycin can directly downregulate the level of miR-26a/b in HCC cells. In turn, restoring the expression of miR-26a/b inhibited autophagy induced by Dox and promoted apoptosis in HCC cells. Further mechanistic study identified that miR-26a and miR-26b target ULK1, a critical initiator of autophagy, at post-transcriptional level. Results from 30 cases of patients with HCC also showed that tumor cellular levels of miR-26a and miR-26b are significantly downregulated as compared with the corresponding control tissues and negatively correlated with the protein level of ULK1 but are not correlated to the mRNA level of ULK1. Gain- and loss-of-function assay confirmed that miR-26a/b inhibited autophagic flux at the initial stage through targeting ULK1. Overexpression of miR-26a/b enhanced the sensitivity of HCC cells to Dox and promoted apoptosis via inhibiting autophagy in vitro. Using xenograft models in nude mice, we confirmed that miR-26a/b, via inhibiting autophagy, promoted apoptosis and sensitized hepatomas to Dox treatment in vivo. Our findings demonstrate for the first time that miR-26a/b can promote apoptosis and sensitize HCC to chemotherapy via suppressing the expression of autophagy initiator ULK1, and provide the reduction of miR-26a/b in HCC as a novel mechanism of tumor chemoresistance.
Evidence that offspring traits can be shaped by parental life experiences in an epigenetically inherited manner paves a way for understanding the etiology of depression. Here, we show that F1 offspring born to F0 males of depression-like model are susceptible to depression-like symptoms at the molecular, neuronal, and behavioral levels. Sperm small RNAs, and microRNAs (miRNAs) in particular, exhibit distinct expression profiles in F0 males of depression-like model and recapitulate paternal depressive-like phenotypes in F1 offspring. Neutralization of the abnormal miRNAs in zygotes by antisense strands rescues the acquired depressive-like phenotypes in F1 offspring born to F0 males of depression-like model. Mechanistically, sperm miRNAs reshape early embryonic transcriptional profiles in the core neuronal circuits toward depression-like phenotypes. Overall, the findings reveal a causal role of sperm miRNAs in the inheritance of depression and provide insight into the mechanism underlying susceptibility to depression.
BackgroundThe origin and development of breast cancer remain complex and obscure. Recently, microRNA (miRNA) has been identified as an important regulator of the initiation and progression of breast cancer, and some studies have shown the essential role of miR-124-3p as a tumor suppressor in breast tumorigenesis. However, the detailed role of miR-124-3p in breast cancer remains poorly understood.MethodsQuantitative RT-PCR and western blotting assays were used to measure miR-124-3p and CBL expression levels in breast cancer tissues, respectively. Luciferase reporter assay was employed to validate the direct targeting of CBL by miR-124-3p. Cell proliferation and invasion assays were performed to analyze the biological functions of miR-124-3p and CBL in breast cancer cells.ResultsIn the present study, we found that miR-124-3p was consistently downregulated in breast cancer tissues. Moreover, we showed that miR-124-3p significantly suppressed the proliferation and invasion of breast cancer cells. In addition, we investigated the molecular mechanism through which miR-124-3p contributes to breast cancer tumorigenesis and identified CBL (Cbl proto-oncogene, E3 ubiquitin protein ligase) as a direct target gene of miR-124-3p. Moreover, we found that ectopic expression of CBL can attenuate the inhibitory effect of miR-124-3p on cell proliferation and invasion in breast cancer cells.ConclusionsThis study identified a new regulatory axis in which miR-124-3p and CBL regulate the proliferation and invasion of breast cancer cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2862-4) contains supplementary material, which is available to authorized users.
Background Progranulin (PGRN), as a multifunctional growth factor, is overexpressed in multiple tumors, but the role of PGRN on tumor immunity is still unclear. Here, we studied the effect of PGRN on breast cancer tumor immunity and its possible molecular mechanism. Methods The changes of macrophage phenotypes after PGRN treatment were detected by western blot, quantitative polymerase chain reaction (PCR) and flow cytometry. Western blot was used to study the signal molecular mechanism of PGRN regulating this process. The number and localization of immune cells in Wild-type (WT) and PGRN−/− breast cancer tissues were analyzed by immunohistochemical staining and immunofluorescence techniques. The activation and proliferation of CD8+ T cells were measured by flow cytometry. Results After being treated with PGRN, the expressions of M2 markers and programmed death ligand 1 (PD-L1) on macrophages increased significantly. Signal transducer and activator of transcription 3 (STAT3) signaling pathway inhibitor Stattic significantly inhibited the expression of PD-L1 and M2 related markers induced by PGRN. In WT group, CD8 were co-localized with macrophages and PD-L1, but not tumor cells. The number of immune cells in PGRN−/− breast cancer tissue increased, and their infiltration into tumor parenchyma was also enhanced. Moreover, in the co-culture system, WT peritoneal macrophages not only reduced the ratio of activated CD8+ T cells but also reduced the proportion of proliferating CD8+ T cells. The addition of programmed death receptor 1 (PD-1) and PD-L1 neutralizing antibodies effectively reversed this effect and restored the immune function of CD8+ T cells. Conclusion These results demonstrate that PGRN promotes M2 polarization and PD-L1 expression by activating the STAT3 signaling pathway. Furthermore, through PD-1/PD-L1 interaction, PGRN can promote the breast tumor immune escape. Our research may provide new ideas and targets for clinical breast cancer immunotherapy.
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