The poor prognosis of patients with ovarian cancer is mainly due to cancer progression. γ-Synuclein (SNCG) has reported as a critical player in cancer metastasis. However, its biological roles and mechanism are yet incompletely understood in ovarian cancer, especially in high-grade serous ovarian cancer (HGSOC). This is a retrospective study of 312 patients with ovarian cancer at a single center between 2006 and 2016. Ovarian cancer tissues were stained by immunohistochemistry to analyze the relationship between SNCG expression and clinicopathologic factors. The clinical outcomes versus SNCG expression level were evaluated by Kaplan–Meier method and multiple Cox regression analysis. Next, systematical functional experiments were given to examine the proliferation and metastatic abilities of SNCG both in vitro and in vivo using loss- and gain- of function approaches. Furthermore, the mechanisms of SNCG overexpression were examined by human phospho-kinase array kit and western blot analysis. Clinically, the expression of SNCG was significantly upregulated in ovarian cancer compared with the borderline and benign tumor, normal ovary, and fallopian tube. Notably, the high level of SNCG correlated with high-risk clinicopathologic features and showed poor survival for patients with HGSOC, indicating an independent prognostic factor for these patients. Functionally, we observed that overexpression of SNCG promoted cell proliferation, tumor formation, migration, and invasion both in vitro and in vivo. Mechanistically, we identified that SNCG promoted cancer cell metastasis through activating the PI3K/AKT signaling pathway. Our results reveal SNCG up-regulation contributes to the poor clinical outcome of patients with HGSOC and highlight the metastasis-promoting function of SNCG via activating the PI3K/Akt signaling pathway in HGSOC.

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SNCG promotes the progression and metastasis of high-grade serous ovarian cancer via targeting the PI3K/AKT signaling pathway.

Targeting the tumour microenvironment in platinum-resistant ovarian cancer

The tRNA-derived fragments (tRFs) and tRNA halves (tiRNAs) are newly discovered noncoding RNAs in recent years. They are derived from specific cleavage of mature and pre-tRNAs and expressed in various cancers. They enhance cell proliferation and metastasis or inhibit cancer progression. Many studies have investigated their roles in the diagnosis, progression, metastasis, and prognosis of various cancers, but the mechanisms through which they are involved in resistance to cancer treatment are unclear. This review outlines the classification of tRFs and tiRNAs and their mechanisms in cancer drug resistance, thus providing new ideas for cancer treatment.

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Mechanisms of tRNA-derived fragments and tRNA halves in cancer treatment resistance

Lipids are essential constituents for malignant tumors, as they are absolutely required for tumor growth and dissemination. Provided by the tumor microenvironment (TME) or by cancer cells themselves through activation of de novo synthesis pathways, they orchestrate a large variety of pro-tumorigenic functions. Importantly, TME cells, especially immune cells, cancer-associated fibroblasts (CAFs) and cancer-associated adipocytes (CAAs), are also prone to changes in their lipid content, which hinder or promote tumor aggressiveness. In this review, we address the significant findings for lipid contribution in tumor progression towards a metastatic disease and in the poor response to therapeutic treatments. We also highlight the benefits of targeting lipid pathways in preclinical models to slow down metastasis development and overcome chemo-and immunotherapy resistance. 

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Lipids in cancer: a global view of the contribution of lipid pathways to metastatic formation and treatment resistance

Background Hepatocellular carcinoma (HCC) is the fourth most common malignant tumor in China. Temozolomide (TMZ) is a common chemotherapy drug which can effectively kill HCC cells in vitro. However, it is possible that HCC cells possess intrinsic resistance to TMZ. A key mechanism of TMZ resistance is the overexpression of O6-methylguanine-DNA methyltransferase (MGMT). Studies have shown that MAPK may be related to MGMT expression, U0126 is a highly selective inhibitor of MEK1 and MEK2, which were crucial molecule in cascade of mitogen-activated protein kinase/extracellular signal regulated kinase (MAPK/ERK) pathway. Sorafenib was another widely applicated target drug in HCC which could inhibit multiple kinases including MAPK/ERK. This research was aimed to investigate the efficacy of MAPK/ERK inhibitor U0126 and sorafenib combine with TMZ in the treatment of HCC. Methods In HCC cells, MAPK/ERK signaling pathway was blocked by U0126 and sorafenib. The effect of blocking MAPK/ERK signaling pathway on TMZ-induced cytotoxicity was evaluated by MTT assay, flow cytometry and TUNEL assay. DNA damage protein and the expression of MGMT were detected by Western-blot. After the downregulation of MAPK/ERK signaling pathway, MGMT mRNA expression and the protein expression of MGMT were quantified by quantitative real-time polymerase chain reaction (RT-qPCR) and immunofluorescence assay, respectively. HepG2 cells were transfected with an MGMT over expression plasmid. After transfection, the effect of U0126 on TMZ-induced cytotoxicity was evaluated by MTT and Western-Blot in MGMT OE cells. The influence of Sorafenib on TMZ-induced cytotoxicity to HCC cells was also detected by MTT assay. Results U0126 can enhance the chemosensitivity of HCC cells to TMZ. At the same time, we also found that U0126 increases the damage to DNA caused by TMZ in HepG2 cells. Moreover, the results from RT-qPCR and Western blot showed that U0126 downregulated MGMT mRNA and MGMT protein expression via blocking MAPK/ERK pathway. Furthermore, after transfection with an MGMT expression plasmid, overexpression of MGMT restored U0126-induced chemosensitivity to TMZ in HCC cells. Sorafenib can also increase the chemosensitivity of HCC cells to TMZ. Conclusions Our studies suggest great clinical potential for the utilization of combined U0126 and TMZ in patients with advanced HCC.

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Lingegowda S. Mangala

Papers

PTGER3 induces ovary tumorigenesis and confers resistance to cisplatin therapy through up-regulation Ras-MAPK/Erk-ETS1-ELK1/CFTR1 axis.