Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor. Patients diagnosed with GBM have a poor prognosis, and it has been reported that tumor malignancy and GBM recurrence are promoted by STAT3 signaling. As resveratrol (RV), a polyphenol in grapes, is reported to be a potent and non-toxic cancer-preventive compound, the aim of this study was to investigate the therapeutic effect and molecular mechanisms of RV on GBM-derived radioresistant tumor initiating cells (TIC). Firstly, our results showed that primary GBM-CD133(+) TIC presented high tumorigenic and radiochemoresistant properties as well as increased protein levels of phosphorylated STAT3. We consistently observed that treatment with shRNA-STAT3 (sh-STAT3) or AG490, a STAT3 inhibitor, significantly inhibited the cancer stem-like cell properties and radioresistance of GBM-CD133(+) in vitro and in vivo. Furthermore, treatment of GBM-CD133(+) with 100 µM RV induced apoptosis and enhanced radiosensitivity by suppressing STAT3 signaling. Microarray results suggested that RV or AG490 inhibited the stemness gene signatures of GBM-CD133(+) and facilitated the differentiation of GBM-CD133(+) into GBM-CD133(-) or astrocytoma cells. Finally, xenotransplant experiments indicated that RV or sh-STAT3 therapy could significantly improve the survival rate and synergistically enhance the radiosensitivity of radiation-treated GBM-TIC. In summary, RV can reduce in vivo tumorigenicity and enhance the sensitivity of GBM-TIC to radiotherapies through the STAT3 pathway.
Liver kinase B1 (LKB1) loss in lung adenocarcinoma is commonly caused by genetic mutations, but these mutations rarely occur in Asian patients. We recently reported wild-type LKB1 loss via the alteration of NKX2-1/p53-axis-promoted tumor aggressiveness and predicted poor outcomes in cases of lung adenocarcinoma. The mechanistic action of wild-type LKB1 loss within tumor progression remains unknown. The suppression of MYC by LKB1 controls epithelial organization; therefore, we hypothesize that MYC expression can be increased via wild-type LKB1 loss and promotes tumor progression. Here, MYC transcription is upregulated by LKB1-loss-mediated MZF1 expression. The wild-type LKB1-loss-mediated MZF1/MYC axis is responsible for soft-agar growth, migration and invasion in lung adenocarcinoma cells. Moreover, wild-type LKB1 loss-induced cell invasiveness was markedly suppressed by MYC inhibitors (10058-F4 and JQ1). Patients with low-LKB1/high-MZF1 or low-LKB1/high-MYC tumors have shorter overall survival and relapse-free-survival periods than patients with high-LKB1/low-MZF1 or high-LKB1/low-MYC tumors. In summary, MZF1-mediated MYC expression may promote tumor progression, resulting in poor outcomes in cases of lung adenocarcinoma with low-wild-type-LKB1 tumors.
Abstract. Oral squamous cell carcinoma (OSCC) is a prevalent cancer worldwide. Let-7 family has been shown to function as a tumor suppressor through regulating multiple oncogenic signaling. Recent study reported that combined underexpression of miR-205 and let-7d showed negative correlation with the survival prognosis of head and neck cancer patients. However, the let-7d-involved mechanism in regulating OSCC is still unclear. In this study, we first demonstrated that let-7d expression was significantly decreased while Twist and Snail expression was increased in OSCC cancer cell lines and primary cultures as compared to normal human oral keratinocyte cells. To further investigate the role of let-7d in OSCC, we applied the SPONGE method to knock down let-7d in OECM-1 and two primary OSCC cell types. The results showed that knockdown of let-7d promote epithelialmesenchymal transition (EMT) traits and migratory/invasive capabilities in OSCC cells. Furthermore, down-expression of let-7d significantly activated Twist and Snail expressions and chemo-resistant abilities of OSCC cells. Notably, overexpression of let-7d effectively reversed the EMT phenotype, blocked migratory/invasive abilities, and further increased the chemosensitivity in oral cancer tumor initiating ALDH1 + cells. In sum, these results show that let-7d negatively modulates EMT expression and also plays a role in regulating chemo-resistant ability in oral cancer. IntroductionHead and neck squamous cell carcinoma, including oral squamous cell carcinoma (OSCC), is the sixth most prevalent malignancy worldwide and accounts for approximately 8-10% of all cancers in Southeast Asia (1,2). The prognosis of OSCC remains dismal as more than 50% of the patients die of this disease or complications within 5 years under current therapies (2). To increase patient survival rate, investigations elucidating the mechanisms of tumorigenesis in OSCC are urgently needed (2). Some studies have suggested that subsets of cancer stem cells (CSC) or tumor initiating cells (TICs) are responsible for tumor progression as well as recurrence after conventional chemotherapy (3). However, there is lack of suitable markers for isolating the crucial subset of tumor cells that is capable of reforming new tumors in vivo and accounts for tumor relapse in OSCC, according to CSC hypothesis of tumorigenesis.MicroRNAs (miRNAs), highly conserved small RNA molecules that regulate gene expression, can act as cancer signatures, oncogenes or tumor suppressors (4). The ubiquitously expressed let-7/miR-98 family was one of the first mammalian miRNAs to be identified (5-8). Let-7 family members have been described as being down-regulated during cancer progression in various human cancers including lung, gastric, ovarian, colon cancer, leiomyoma and melanoma (5-13). Let-7d, a member of the let-7 family of miRNAs, has also been shown to act as tumor suppressor, most likely through targeting RAS (14) or high mobility group A2 (15). Let-7d regulates senescence of human cord blood-derived multipotent ste...
Quercetin suppressing HNC-TICs characteristics may therefore be valuable therapeutics clinically in combination with standard treatment modalities.
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