Guopei Zheng

Chemoresistance to 5-fluorouracil induces epithelial–mesenchymal transition via up-regulation of Snail in MCF7 human breast cancer cells

5-Fluorouracil (5-FU) is commonly used to treat breast cancer; however, it becomes increasingly ineffective with tumor progression. Epithelial-to-mesenchymal transition (EMT) is a process whereby cells acquire morphologic and molecular alterations facilitating tumor metastasis and progression. Emerging evidence associates chemoresistance with acquisition of EMT in cancer. However, it is not clear whether this phenomenon is involved in acquired resistance to 5-FU. Using a previously established in vitro cell model of 5-fluorouracil-resistant MCF7 cells (MCF7/5-FU), we assessed the cellular morphology, molecular changes, migration and invasion consistent with EMT. We found that silencing of Snail by stable RNA interference reversed the EMT and greatly abolished invasion behavior of MCF7/5-FU cells. We also showed that inhibition of Snail increased the sensitivity of 5-FU-resistant cells to 5-FU. Our study provided a new insight into EMT-like phenotypic changes associated with 5-FU resistance in MCF7 cells. We believed that down-regulation of Snail could be a potential novel therapeutic approach to overcoming chemoresistance and preventing metastasis during 5-FU chemotherapy.

Microarray-Assisted Pathway Analysis Identifies MT1X & NFκB as Mediators of TCRP1-Associated Resistance to Cisplatin in Oral Squamous Cell Carcinoma

We recently reported that TCRP1, a novel multidrug-resistance associated human gene, can mediate cisplatin resistance in OSCC cells. However, the molecular mechanism underlying this role of TCRP1 remained to be elucidated. In this study, by using Human Toxicology and Drug Resistance Microarray, we identified 30 genes with significantly different expression levels between Tca/PYM and TCRP1 knockdown cell lines. Co-immunoprecipitation experiments and GST-pull down assays showed that metallothionein1X (MT1X) and Akt interact with TCRP1. siRNA-mediated knockdown of TCRP1 and MT1X was found to sensitize cells to cisplatin, leading to increased apoptosis and inhibition of cell proliferation. These functions of TCRP1 may be caused at least in part via activation of the PI3K/Akt/NF-κB signaling pathway. Taken together, our findings indicate that TCRP1 may be an important drug target for improvement of the treatment and survival of patients with oral squamous cell carcinoma.

TCRP1 promotes radioresistance of oral squamous cell carcinoma cells via Akt signal pathway

Tongue cancer resistance-associated protein 1 (TCRP1) is a novel gene located on human chromosome 11q13.4 which has been reported as a candidate related to chemotherapeutic resistance to cisplatin. Results suggest that TCRP also contribute to radioresistance in oral squamous cell carcinoma (OSCC) cells. We previously established exogenous overexpression of TCRP1 cell line Tca8113/TCRP1 and TCRP1 knockdown cell line Tca8113/PYM-siRNA and paired control cell lines, which provides a cell model system to investigate the roles and mechanisms of TCRP1-mediated radioresponse in OSCC. In this study, we first compared the radiosensitivity of up/down-regulating expression of TCRP1 cell lines and paired control cell lines by a clonogenic survival assay, Hoechst 33258 staining, cell growth assay, and comet assay. The results indicated that TCRP1 played a significant role in mediating OSCC radioresistance through decreased cells apoptosis and increased cellular proliferation and long-term survival. The further study found that TCRP1 function by up-regulating Akt activity and levels and then elevating the level of NF-κB. In summary, these results provided strong evidence for the linkage between TCRP1 and radiation sensitivity and may provide theoretical base of TCRP1 as a potential molecular mark of estimating the response for irradiation in OSCC.

Cloning and functional characterization of TCRP1, a novel gene mediating resistance to cisplatin in an oral squamous cell carcinoma cell line.

To explore the mechanisms of chemotherapy resistance, we previously established a multi‐drug resistant cell line, Tca8113/Pingyangmycin (Tca8113/PYM) and identified differential expression in known genes and ESTs using microarray analysis. From among those ESTs we have now identified a novel gene producing an mRNA of 1834 nucleotides translated into a protein having 235 amino acids. This gene was denominated as tongue cancer resistance‐associated protein 1 gene (TCRP1, accession number: EF363480). We further determined its functional characteristics. The results demonstrate that TCRP1 mediates a specific resistance to cisplatin in Tca8113 cells by reducing the cisplatin‐induced apoptosis. This suggests that TCRP1 might be a novel molecular target to develop agents to reverse cisplatin‐induced chemoresistance.

14‐3‐3σ regulation by p53 mediates a chemotherapy response to 5‐fluorouracil in MCF‐7 breast cancer cells via Akt inactivation

We previously demonstrated that 14‐3‐3σ was downregulated in 5‐fluorouracil (5‐Fu)‐resistant MCF‐7 breast cancer cells (MCF‐7/5‐Fu). Here, we found that stably enhanced 14‐3‐3σ expression strengthened the effects of 5‐Fu, Mitoxantrone and cDDP. 14‐3‐3σ stabilised the p53 protein and bound Akt to inhibit its activity and its downstream targets: survivin, Bcl‐2 and NF‐κB‐p50. In addition, decreased p53 expression, but not promoter hypermethylation, was responsible for the downregulation of 14‐3‐3σ in MCF‐7/5‐Fu cells. Meanwhile, initial treatments with high concentrations of 5‐Fu clearly induced 14‐3‐3σ and p53 expression in a time‐dependent manner. 14‐3‐3σ‐mediated molecular events that synergise with p53 may play important roles in the chemotherapy of breast cancer.

Purification and biochemical characterization of a novel protein-tongue cancer chemotherapy resistance-associated protein1 (TCRP1).

Multidrug resistance is a major obstacle to successful treatment of oral squamous cell carcinoma (OSCC). Lately, we found a novel human gene named tongue cancer chemotherapy resistance-associated protein1 (TCRP1) in the tongue cancer multi-drug resistance cell line (Tca8113/PYM) established by us. In this study, we focus on recombinant expression, purification, and biochemical characterization of TCRP1. After molecular cloning and purification of the gene encoding the 24-kDa protein, a mouse polyclonal antibody against TCRP1 was prepared, and the specialty of the antibody was confirmed by Western blot. The cell proliferation was evaluated by MTS assay and DNA damage was determined by comet assay, the results indicated that this protein especially mediated the cells resistance to cisplatin; it was associated with its role of providing protection against DNA damage. We also found that TCRP1 expression was increased in cisplatin-resistant carcinoma cell lines (Tca/PYM and A549/DDP), but not in cisplatin-sensitive MDR cell lines (MCF-7/5-Fu), compared with their parental counterparts by Western blot analysis. Immunofluorescence and immunohistochemical analysis showed TCRP1 is mainly expression in cytoplasmic, the Mann-Whitney U test exhibited that TCRP1 positive patients predicted the worst sensitive with cisplatin of OSCC patients. All these findings suggest that TCRP1 is a novel cisplatin-resistant protein which is mainly localized in the cytoplasm and can mediate cisplatin resistance against DNA damage; the expression level of TCRP1 in patients with OSCC may be useful as an indicator of therapeutic efficacy of the sensitivity to cisplatin.

Inhibition of proliferation and induction of G1-phase cell-cycle arrest by dFMGEN, a novel genistein derivative, in lung carcinoma A549 cells.

Genistein (GEN) is a molecule of great interest as a potent chemopreventive agent against atherosclerosis and cancer. However, the bioavailability of GEN is very low in vivo. Our previous study showed that a GEN derivative, 7-difluoromethyl-5,4′-dimethoxygenistein (dFMGEN) has a better bioavailability than GEN in vivo. In this study, we further evaluated the efficacy of dFMGEN as a candidate for cancer therapy. We demonstrated that dFMGEN treatment decreased the viability of A549 cells in a concentration- and time-dependent manner and induced cell-cycle arrest at the G1 phase. G1 phase arrest was correlated with a significant reduction of Cdk4 and cyclin D1 protein level. Further studies showed that cyclin-dependent kinase (Cdk)4 and cyclin D1 protein-level decrease was caused by Cdk inhibitors p15, p21, and p27 level increase, and decreased protein level directly suppressed Rb protein phosphorylation and E2F-1 expression, then cell-cycle progression was arrested. Finally, we also found that dFMGEN has a dosage effect in suppressing tumor growth in vivo, and that dFMGEN was well tolerated by animals. In summary, our results suggest that dFMGEN has therapeutic potential for the treatment of human lung cancer.

Inhibition of growth and motility of human A549 lung carcinoma cells by a recombined vascular basement membrane derived peptide.

We have previously constructed a recombined vascular basement membrane derived multifunctional peptide (rVBMDMP) which can inhibit tumor growth. The aim of this study is to explore the effects and mechanisms of rVBMDMP on growth and motility/invasion in human A549 lung carcinoma cells. The effect of rVBMDMP on A549 cell viability was determined by MTT assay while the motility/invasion was measured by scratch and transwell assays. Molecules that responded to rVBMDMP treatment of A549 cells were explored using the high-throughput Cancer Pathway Finder cDNA Microarray. We identified 16 genes that were up-regulated, including GZMA, ITG alphaV, MCAM and Kiss1 and 21 genes that were down-regulated, including uPA, uPAR, CDC25A, IGF1 and FGF2. Selective differentially expressed genes were further analyzed by real-time quantitative PCR and Western blot analysis. These findings contribute to the understanding of the molecular mechanisms mediating rVBMDMP action, and suggest that rVBMDMP is a promising novel agent for the treatment of human lung carcinoma.