Chemoresistance Of Gastric Cancer Cells Research Articles

Interleukin-8 associates with adhesion, migration, invasion and chemosensitivity of human gastric cancer cells

To investigate the relationship between Interleukin-8 (IL-8) and proliferation, adhesion, migration, invasion and chemosensitivity of gastric cancer (GC) cells. The IL-8 cDNA was stably transfected into human GC cell line MKN-45 and selected IL-8-secreting transfectants. The expression of IL-8 in human GC cell line KATO-III was inhibited by RNA interference. The expressions of mRNA and protein of IL-8 in GC cells were detected by real-time reverse transcription-polymerase chain reaction or enzyme-linked immunosorbent assay (ELISA). The overexpression of IL-8 resulted in an increased cell adhesion, migration and invasion, and a significant resistance to oxaliplatin in MKN-45 cells. Inhibition of IL-8 expression with small interfering RNA decreased the adhesion, migration and invasion functions and oxaliplatin resistance in KATO-III cells. IL-8 increased NF-κB and Akt activities and adhesion molecules ICAM-1, VCAM-1, and CD44 expression in GC cells. Overexpression of IL-8 promotes the adhesion, migration, invasion, and chemoresistance of GC cells, indicating that IL-8 is an important therapeutic target in GC.

Akt associates with nuclear factor κB and plays an important role in chemoresistance of gastric cancer cells

The ubiquitously expressed serine-threonine kinase Akt and the transcription factor NF-kappaB both are involved in cell proliferation and apoptosis. Furthermore, the activation of Akt or NF-kappaB has been suggested to associate with chemo-resistance of human tumors. The exact mechanism and interreaction of Akt and NF-kappaB pathway on chemoresistance in gastric cancer is still unknown. We explored the function of Akt and NF-kappaB pathway on chemoresistance in human gastric cancer cells. MTT method was used to analyze the influence of chemotherapeutics and the combined use of wortmannin or MG-132 on the growth of SGC-7901 cells. Apoptosis of SGC-7901 was detected by TUNEL and Annexin V/PI methods. The protein level of NF-kappaB was analyzed by immunocytochemical staining. EMSA was used to confirm the increased nuclear translocation of RelA. The protein level of p-Akt and p-IkappaBalpha were analyzed by Western blotting. Etoposide and doxorubicin suppressed the growth of SGC-7901 time and dose-dependently. Combined use of wortmannin or MG-132 can suppress growth further. Chemotherapeutics induced apoptosis of SGC-7901 and activated Akt and NF-kappaB, combined use of wortmannin or MG-132 induced apoptosis further and attenuated the activation of NF-kappaB. The combined use of wortmannin attenuated the activation of Akt, but combined use of MG-132 did not attenuate the activation of Akt. The activation of NF-kappaB is a branch mechanism of Akt anti-apoptosis effects. The chemotherapeutics induced apoptosis and induced the activation of Akt and NF-kappaB in SGC-7901 cell, suppression the activation of Akt or NF-kappaB can increase the effects of chemotherapeutics. NF-kappaB is a downstream target of Akt.

Phosphoinositide 3‐kinase/Akt pathway plays an important role in chemoresistance of gastric cancer cells against etoposide and doxorubicin induced cell death

The major obstacle to successful treatment of gastric cancer is chemotherapy resistance. Our study was designed to investigate the role of phosphoinositide 3-kinase (PI3K)/Akt pathway in the development of chemoresistance in gastric cancer. In the present study, elevated Akt expression and Akt phosphorylation (Ser 473), as well as decreased PTEN expression were observed in 28 cases of gastric cancer tissues. Etoposide and doxorubicin stimulated Akt and PI3K activities in 2 gastric cancer cell lines (BGC-823 and SGC-7901), and the activities were concentration and time-dependent. Up-regulation of PTEN expression in BGC-823 cells by PEAK8-PTEN transient transfection obviously decreased the basal and anticancer drugs induced Akt activities, then sensitized BGC-823 cells to etoposide and doxorubicin. Pretreatment of BGC-823 and SGC-7901 cells with wortmannin, a PI3K inhibitor, attenuated cells's resistance to etoposide and doxorubicin. In addition, pretreatment of wortmannin blocked etoposide and doxorubicin induced IkappaB-alpha degradation, NFkappaB activation, phosphorylation of Akt, MDM-2 and forkhead transcription factors. Wortmannin pretreatment also promoted the accumulation of p27/Kip, but inhibited the Mcl-1 expression. Furthermore, wortmannin promoted etoposide and doxorubicin induced caspase-3, caspase-9 activation and poly ADP-ribose polymerase cleavage. Taken together, the observations indicate the PI3K/Akt pathway plays an important role in the chemoresistance of gastric cancer cells. A new strategy for combined chemotherapy of gastric cancer should be designed to more specifically block PI3K/Akt pathway and then decrease the amount of resistant cells.

Activation of Akt and ERK signalling pathways induced by etoposide confer chemoresistance in gastric cancer cells

Aims To identify whether phosphatidylinositol 3-kinase/Akt and mitogen-activated protein kinase/extracellular-regulated protein kinases signalling pathways are implicated in the chemoresistance of gastric cancer and to explore the possible mechanisms. Methods Gastric cancer cell lines SGC7901 and BGC823 were exposed to etoposide, Wortmannin + etoposide or PD98059 + etoposide. Cell cycle distribution and cell apoptosis were detected using flow cytometry and Hoechst 33258 staining. Cells viability was determined by a colourimetric assay utilising 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). Akt activity was detected using non-radioactive immunoprecipitation-kinase assay. Western blotting was exploited to evaluate the level of phosphorylated ERK1/2 and expressions of c-Myc and p53 protein. Results Etoposide suppressed the viability of SGC7901 and BGC823 cells in a time- and dose-dependent manner; PD98059 and Wortmannin were able to enhance the cytotoxicity of etoposide. The apoptotic levels of cells treated with Wortmannin + etoposide or PD98059 + etoposide were significantly higher than those of cells treated with etoposide only. Phospho-ERK1/2, Akt activity and expression of c-Myc were significantly induced by etoposide in a time-dependent manner; moreover, there was a weak effect on the expression of p53 protein. Both Wortmannin and PD98059 elevated the level of p53 expression strikingly, however, only PD98059 suppressed the up-regulation trend of c-Myc expression induced by etoposide. Conclusion Chemotherapy reagent activated phosphatidylinositol 3-kinase/Akt and mitogen-activated protein kinase/extracellular-regulated protein kinases signalling pathways, which decreased the chemotherapy sensitivity of gastric cancer cell lines SGC7901 and BGC823 via suppressing the expression of p53 and enhancing the expression of c-Myc. This may be one of the molecular mechanisms of gastric cancer chemoresistance.

Characterization of RhoA-mediated Chemoresistance in Gastric Cancer Cells

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 reduction in 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.