SAHA Overcomes 5-FU Resistance in IFIT2-Depleted Oral Squamous Cell Carcinoma Cells

IFIT2 Depletion Promotes Cancer Stem Cell-like Phenotypes in Oral Cancer

(1) Background: Cancer stem cells (CSCs) are a small cell population associated with chemoresistance, metastasis and increased mortality rate in oral cancer. Interferon-induced proteins with tetratricopeptide repeats 2 (IFIT2) depletion results in epithelial to mesenchymal transition, invasion, metastasis, and chemoresistance in oral cancer. To date, no study has demonstrated the effect of IFIT2 depletion on the CSC-like phenotype in oral cancer cells. (2) Methods: Q-PCR, sphere formation, Hoechst 33,342 dye exclusion, immunofluorescence staining, and flow cytometry assays were performed to evaluate the expression of the CSC markers in IFIT2-depleted cells. A tumorigenicity assay was adopted to assess the tumor formation ability. Immunohistochemical staining was used to examine the protein levels of IFIT2 and CD24 in oral cancer patients. (3) Results: The cultured IFIT2 knockdown cells exhibited an overexpression of ABCG2 and CD44 and a downregulation of CD24 and gave rise to CSC-like phenotypes. Clinically, there was a positive correlation between IFIT2 and CD24 in the patients. IFIT2high/CD24high/CD44low expression profiles predicted a better prognosis in HNC, including oral cancer. The TNF-α blockade abolished the IFIT2 depletion-induced sphere formation, indicating that TNF-α may be involved in the CSC-like phenotypes in oral cancer. (4) Conclusions: The present study demonstrates that IFIT2 depletion promotes CSC-like phenotypes in oral cancer.

IFIT2-depleted metastatic oral squamous cell carcinoma cells induce muscle atrophy and cancer cachexia in mice

BACKGROUND

Interferon-induced protein with tetratricopeptide repeat 2 (IFIT2) is a reported metastasis suppressor in oral squamous cell carcinoma (OSCC). Metastases and cachexia may coexist. The effect of cancer metastasis on cancer cachexia is largely unknown. We aimed to address this gap in knowledge by characterizing the cachectic phenotype of an IFIT2-depleted metastatic OSCC mouse model.

METHODS

Genetically engineered and xenograft tumour models were used to explore the effect of IFIT2-depleted metastatic OSCC on cancer cachexia. Muscle and organ weight changes, tumour burden, inflammatory cytokine profiles, body composition, food intake, serum albumin and C-reactive protein (CRP) levels, and survival were assessed. The activation of the IL6/p38 pathway in atrophied muscle was measured.

RESULTS

IFIT2-depleted metastatic tumours caused marked body weight loss (-18.2% vs. initial body weight, P < 0.001) and a poor survival rate (P < 0.01). Skeletal muscles were markedly smaller in IFIT2-depleted metastatic tumour-bearing mice (quadriceps: -28.7%, gastrocnemius: -29.4%, and tibialis: -24.3%, all P < 0.001). Tumour-derived circulating granulocyte-macrophage colony-stimulating factor (+772.2-fold, P < 0.05), GROα (+1283.7-fold, P < 0.05), IL6 (+245.8-fold, P < 0.001), IL8 (+616.9-fold, P < 0.001), IL18 (+24-fold, P < 0.05), IP10 (+18.8-fold, P < 0.001), CCL2 (+439.2-fold, P < 0.001), CCL22 (+9.1-fold, P < 0.01) and tumour necrosis factor α (+196.8-fold, P < 0.05) were elevated in IFIT2-depleted metastatic tumour-bearing mice. Murine granulocyte colony-stimulating factor (+61.4-fold, P < 0.001) and IL6 (+110.9-fold, P < 0.01) levels were significantly increased in IFIT2-depleted metastatic tumour-bearing mice. Serum CRP level (+82.1%, P < 0.05) was significantly increased in cachectic shIFIT2 mice. Serum albumin level (-26.7%, P < 0.01) was significantly decreased in cachectic shIFIT2 mice. An assessment of body composition revealed decreased fat (-81%, P < 0.001) and lean tissue (-21.7%, P < 0.01), which was consistent with the reduced food intake (-19.3%, P < 0.05). Muscle loss was accompanied by a smaller muscle cross-sectional area (-23.3%, P < 0.05). Muscle atrophy of cachectic IFIT2-depleted metastatic tumour-bearing mice (i.v.-shIFIT2 group) was associated with elevated IL6 (+2.7-fold, P < 0.05), phospho-p38 (+2.8-fold, P < 0.05), and atrogin-1 levels (+2.3-fold, P < 0.05) in the skeletal muscle. Neutralization of IL6 rescued shIFIT2 conditioned medium-induced myotube atrophy (+24.6%, P < 0.01).

CONCLUSIONS

Our results suggest that the development of shIFIT2 metastatic OSCC lesions promotes IL6 production and is accompanied by the loss of fat and lean tissue, anorexia, and muscle atrophy. This model is appropriate for the study of OSCC cachexia, especially in linking metastasis with cachexia.

The evaluation of the efficacy and potential genotoxic hazard of combined SAHA and 5-FU treatment in the chemoresistant colorectal cancer cell lines

5-Fluorouracil (5-FU) is an essential chemotherapeutic drug for colorectal cancer (CRC) treatment. However, the frequent development of drug resistance has dramatically affected its clinical use. Therefore, novel treatment strategies are critical to improving patient outcomes. Herein, we investigated the ability of the epigenetic drug SAHA to increase the sensitivity of chemoresistant CRC cells to 5-FU. In addition, we evaluated the potential genotoxic risk of SAHA+5-FU combination treatment. As a model system, we used three CRC cell lines, HT-29, SW480, and HT-29/EGFP/FUR, differing in their resistance to 5-FU. CRC cell lines were exposed to sub-toxic SAHA concentrations for 24 h, followed by a 48 h treatment with 5-FU. The cytotoxicity of SAHA, 5-FU, and SAHA+5-FU was measured by the MTT test, the genotoxicity by the comet assay, and the micronucleus test. The apoptotic/necrotic activity was assessed using morphological criteria. We found a synergic decrease in the viability of HT-29 and SW480 cells, but not the most resistant HT-29/EGFP/FUR cells after combined SAHA+5-FU exposure compared to 5-FU. Remarkably, SAHA most efficiently induced apoptosis in HT-29/EGFP/FUR cells compared to HT-29 and SW480 cells. Combined SAHA+5-FU treatment resulted in a synergistic increase in apoptotic/necrotic cells in HT-29 cell line, while rather additive/sub-additive effect was determined in the SW480 and HT-29/EGFP/FUR cells. At the same time, however, a synergistic rise in micronuclei was found in CRC cell lines (at least at some concentrations). We have shown that SAHA can sensitize CRC cells to 5-FU; therefore, epigenetic and convential drug combinations could be beneficial for the patients. However, the increase in micronucleus formation after combined SAHA+5-FU treatment indicates a potential health hazard. The clastogenic activity could contribute to cancer heterogeneity, favoring progeny of such aberrant cells to clonal expansion. Therefore, developing new specific epigenetic drugs or nanocarriers for targeted drug delivery might reduce the potential genotoxic risk.

Dysregulation of the miR-30a/BiP axis by cigarette smoking accelerates oral cancer progression

Background

Cigarette smoking is the most significant cause of oral cancer progression. Cigarette smoke condensate (CSC) has been shown to induce endoplasmic reticulum (ER) stress. Binding immunoglobulin protein (BiP) being as an ER stress regulator, has been reported to be implicated in malignant behaviors. Therefore, the aim of this study was to investigate the role of the ER stress-responsive protein, BiP, in CSC-induced oral squamous cell carcinoma (OSCC) malignancy.

Methods

The biological role of BiP in CSC-induced tumor progression was investigated in OSCC cells (YD38 and SCC25) and in a tumor xenograft mouse model. The expressions of related genes were investigated using quantitative RT-PCR and Western blot analysis. Cell migration and invasion were assessed using scratch wound healing and Transwell invasion assays. The effects of conditioned media from OSCC cells on the angiogenic activities of endothelial cells were analyzed using a tube formation assay. The interaction between miR-30a and BiP mRNA was detected using a luciferase reporter assay.

Results

Our results demonstrated that CSC increased the expression of BiP in time- and dose-dependent manners in YD38 and SCC25 cells, and that silencing BiP abrogated CSC-induced cell invasion and tumor-associated angiogenesis. Notably, the putative miR-30a binding site was observed in the 3′untranslated region (UTR) of BiP mRNA, and miR-30a suppressed BiP expression by targeting 3′UTR of BiP transcript. In addition, CSC increased the expression of BiP in OSCC cells by downregulating miR-30a. We also showed that BiP promoted invasion and tumor-associated angiogenesis by increasing the production and secretion of vascular endothelial growth factor in CSC-exposed OSCC cells. Moreover, BiP inhibition suppressed OSCC growth and reduced tumor vessel density in tumor-bearing mice administered with CSC.

Conclusions

These observations suggest that epigenetic regulation of BiP via miR-30a downregulation is involved in CSC-induced OSCC progression.

Upregulation of histone acetylation reverses organic anion transporter 2 repression and enhances 5-fluorouracil sensitivity in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world. The failure of chemotherapy in HCC patients is partly due to inadequate intracellular drug accumulation caused by abnormally expressed drug transporters. Human organic anion transporter 2 (hOAT2), a transporter mainly expressed in liver and kidney, is responsible for uptake of various antineoplastic drugs such as 5-fluorouracil (5-FU). Among 32 pairs of human HCC samples, we preliminarily found that OAT2 was suppressed in HCC tissues compared with matched tumor-adjacent tissues at both mRNA and protein levels, which resulted in 5-FU resistance in HCC. However, the epigenetic regulatory mechanisms of OAT2 downregulation have not been investigated. In this study, we first proved it was histone hypoacetylation rather than DNA hypermethylation that participated in transcriptional repression of OAT2 in two HCC cell lines (BEL-7402 and SMMC-7721). In general, there were two pathways confirmed using tissues and cells: 1) Increased histone deacetylase sirtuin 7 (SIRT7) mediated loss of histone 3 lysine 18 acetylation (H3K18ac) at the promoter of OAT2 and inhibited its transcription. 2) More histone deacetylase 7 (HDAC7) instead of lysine acetyltransferase 8 (KAT8) enrichment at the promoter of OAT2 led to low levels of histone 4 lysine 16 acetylation (H4K16ac). Further, we found that histone deacetylases inhibitor vorinostat (SAHA) could reverse histone hypoacetylation state to activate OAT2 transcription and enhance uptake of classic OAT2 substrate zidovudine. Therefore, we evaluated the effect of combining SAHA and 5-FU and the results demonstrated that SAHA could sensitize HCC cells to 5-FU. Collectively, we proposed such a combination treatment to overcome 5-FU resistance in HCC from the perspective of epigenetically restoring OAT2.