BackgroundOvarian cancer has the highest ratio of mortality among gynecologic malignancies. Chemotherapy is one of the most common treatment options for ovarian cancer. However, tumor relapse in patients with advanced tumor stage is still a therapeutic challenge for its clinical management.Main bodyTherefore, it is required to clarify the molecular biology and mechanisms which are involved in chemo resistance to improve the survival rate of ovarian cancer patients. Cancer stem cells (CSCs) are a sub population of tumor cells which are related to drug resistance and tumor relapse.ConclusionIn the present review, we summarized the recent findings about the role of CSCs in tumor relapse and drug resistance among ovarian cancer patients. Moreover, we focused on the targeted and combinational therapeutic methods against the ovarian CSCs.

Cancer stem cells, as a subgroup of tumor cells, resemble critical properties of embryonic stem cells (ESCs) such as self-renewal and maintenance of stemness state. SALL4 and SOX2 are two main transcription factors involving in maintenance of pluripotency, self-renewal and cell fate decision in ESCs. In this study, we aimed to elucidate the expression levels of these important transcription factors in esophageal squamous cell carcinoma (ESCC) and to reveal their probable roles in maintenance and progression of the disease. The expression level of SALL4 and SOX2 was analyzed in fresh tumoral tissues in comparison with distant tumor-free tissues of 50 ESCC patients by relative comparative real-time PCR. SALL4 and SOX2 were overexpressed in 64 and 32% of tumor samples, respectively, in significant correlation with each other (p = 0.028). There was a significantly inverse correlation between low level of SALL4 expression and metastasis of tumor cells into the lymph nodes (p = 0.035). Furthermore, co-overexpression of the genes was significantly correlated with the depth of tumor invasion (p = 0.045) and metastasis to the lymph nodes (p = 0.049). SALL4 and SOX2 are co-overexpressed in ESCC and have a significant correlation with invasion and metastasis of the disease. To the best of our knowledge, this is the first report of SALL4 clinical relevance in ESCC to date. The clinical consequences of SALL4-SOX2 association suggest a possible functional interaction between these factors in regulation of ESCC maintenance and aggressiveness and introduce these regulators of stemness state as potentially interesting therapeutic targets to bring new opportunities for onco-therapeutic modalities.

Overexpression of IL-10, TGF-beta, and VEGF plays an important role in ESCC and consequently leads to the frequent event of immune evasion in ESCC. TGF-beta is concomitantly overexpressed with IL-10 and with VEGF in ESCC. A stimulatory signal from TGF-beta to VEGF is necessary for VEGF to promote tumor progression.

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The three amino acid loop extension (TALE) class myeloid ecotropic viral integration site 1 (MEIS1) homeobox gene is known to play a crucial role in normal and tumor development. In contrast with its well-described cancer stemness properties in hematopoietic cancers, little is known about its role in solid tumors like esophageal squamous cell carcinoma (ESCC). Here, we analyzed MEIS1 expression and its clinical relevance in ESCC patients and also investigated its correlation with the SOX2 self-renewal master transcription factor in the ESCC samples and in the KYSE-30 ESCC cell line. MEIS1 mRNA and protein expression were significantly decreased in ESCC disease (P < 0.05). The inverse correlation between MEIS1 mRNA expression and tumor cell metastasis to the lymph nodes (P = 0.004) was significant. Also, MEIS1 protein levels inversely correlated to lymph node involvement (P = 0.048) and high tumor stage (stages III/IV, P = 0.030). The low levels of DNA methylation in the MEIS1 promoter showed that this suppression does not depend on methylation. We showed that downregulation of EZH2 restored MEIS1 expression significantly. Also, we investigated that MEIS1 downregulation is concomitant with increased SOX2 expression. To the best of our knowledge, this is the first report on the MEIS1 gene in ESCC. The inverse correlation of MEIS1 with metastasis, tumor staging, and the role of EZH2 in methylation, together with its correlation with stemness factor SOX2 expression, led us to predict cancer stemness properties for MEIS1 in ESCC.