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Maspin is a tumor suppressor protein that has been reported to stimulate the cell death of cancer and inhibit the metastasis of cancer. The present study aimed to explore the survival pathway by which maspin modulates the resistance of human lung cancer cells to chemotherapeutic drugs, and the consequences of maspin gene therapy in an animal model.
NCI-H157 and A549 cells were transfected with either a mock vector (pCMVTaq4C), maspin (pCMV-maspin), siControl or siMaspin. RT-PCR and Western blot analysis were performed to study the expressions of survival proteins in lung cancer. cDNA microarray analysis was carried out to compare the maspin-modulated gene expression between the xenograft tumors derived from the lung cancer cells that were stably transfected with pCMVTaq4C or pCMV-maspin. Maspin gene therapy was performed by intra-tumoral injections of pCMVTaq4C or pCMV-maspin into the pre-established subcutaneous tumors in nude mice.
Maspin significantly decreased the survival to doxorubicin and etoposide, whereas did not affect the survival to cisplatin in the NCI-H157 cells. Interestingly, transfection with a maspin plasmid resulted in a significant reduction of the phosphorylation of Akt in the NCI-H157 cells, whereas knockdown of maspin increased the phosphorylation of Akt in the A549 cells. Microarray analysis of the xenograft tumors revealed a specific gene expression profile, demonstrating that maspin is associated with the differential expressions of PTEN and IGF2R. Direct transfer of pCMV-maspin into the tumor significantly retarded the tumor growth in the animal experiments (p=0.0048).
Lung cancer cells lacking maspin could be resistant to chemotherapeutic drugs such as doxorubicin or etoposide, at least in part by maintaining Akt phosphorylation.
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RhoA is a critical transducer of extracellular signals, which leads to organization of actin cytoskeleton, motility, adhesion and gene regulation. The present study aimed to explore whether RhoA influences the susceptibility of gastric cancer cells to chemotherapeutic drugs.
SNU638 cells were transfected with a mock vector (pcDNA3.1), RhoA (pcDNA/RhoA), or constitutively active RhoA (pcDNA/caRhoA). MTT assay and Western blot analysis were performed to study the growth response to several chemotherapeutic drugs in the gastric cancer cell line, SNU638, with different RhoA levels.
RhoA significantly enhanced the resistance to lovastatin, 5-FU, taxol and vincristine, but did not affect the sensitivity to cisplatin or etoposide in SNU638. In the Western blot analysis, RhoA decreased the PARP cleavage, which was accompanied by a concurrent reductionin cell death. The gene expression profile after a cDNA microarray analysis demonstrated that RhoA was associated with the differential expression of 19 genes, including those involved in anti-oxidant defense, glucose metabolism, anti-apoptosis and protein turnover.
Gastric cancer cells with a high expression of RhoA could be resistant to chemotherapeutic drugs, such as taxol or vincristine, implying that treatment strategies aimed at inactivation of RhoA might be promising for improving the efficacy of these chemotherapeutic drugs.
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