PI3K/Akt/p27kip1通道介导胃癌细胞对阿霉素、足叶乙甙化疗的耐药性及其机制

P27 expression in colorectal cancer: Significance and correlation with expression of Ki-67, P170, MLH1, MSH2, and MSH6

AIM: To investigate the relationship between P27 expression and tumor invasion, metastasis, multidrug resistance and prognosis of colorectal cancer (CRC), and to explore the possible mechanisms involved.

METHODS: Two hundred and sixty-three sporadic CRC patients who underwent surgery in the Department of Colorectal Surgery, Beijing Cancer Hospital from March 2008 to March 2012 were included in this study. All patients were diagnosed by histological examination and did not undergo chemoradiotherapy before surgery. Immunohistochemistry was used to detect P27, Ki-67, P170, MLH1, MSH2 and MSH6 protein expression in samples from these patients. The association between expression and clinical data was analysed retrospectively.

RESULTS: The positive rates of P27, Ki-67, P170, MLH1, MSH2 and MSH6 expression in CRC were 71.1%, 81.4%, 82.5%, 86.7%, 87.8% and 71.1%, respectively. Deficient expression of P27 was closely associated with tumour size, location, differentiation, invasion depth, vascular invasion and lymph node metastasis, but had no association with patients' gender, age, or tumor macroscopic morphology. P27 expression was negatively correlated with Ki-67 and P170 expression (r = -0.315, -0.163, P = 0.00, 0.01), but positively with MLH1, MSH2 and MSH6 expression (r = 0.129, 0.136, 0.159, P = 0.03, 0.03, 0.01).

CONCLUSION: P27 expression is closely associated with the development, invasion and metastasis of CRC. P27 protein expression can be regarded as an important parameter for evaluation of colorectal cancer progression and for selection of chemotherapy drugs and prevention of multidrug resistance.

Use of p38 MAPK inhibitor reduces resistance of colon cancer cells to doxorubicin

AIM: To evaluate whether SB203580, a p38MAPK inhibitor, reduces resistance of colon cancer HCT-116 cells to doxorubicin and to explore possible mechanisms involved.

METHODS: Doxorubicin alone or in combination with SB203580 was used to treat subcultured HCT-116 cells. After treatment, cell growth was determined by MTT assay, and Akt and p-AKt expression was detected by Western blotting.

RESULTS: Either doxorubicin or SB203580 inhibited HCT-116 cell growth, and the latter had a stronger inhibitory effect than the former (26.60% vs 33.87%). Combined use of doxorubicin and SB203580 had more strong inhibitory effect than treatment with either of them alone (56.04%). Expression of Akt showed no significant difference between cells treated with doxorubicin alone and those treated with combined doxorubicin and SB203580, while the phosphorylation of Akt was significantly higher in the doxorubicin group than in the combination group.

CONCLUSION: The p38 MAPK inhibitor SB203580 could block the Akt signaling pathways and increase the sensitivity of colon cancer cells to doxorubicin.

In vitro antitumor effect of the proteasome inhibitor bortezomib on human gastric cancer SGC7901 cells

AIM: To investigate the anti-tumor effect of bortezomib, a proteasome inhibitor, on human gastric cancer SGC7901 cells and to explore possible mechanism involved.

METHODS: Human gastric cancer SGC7901 cells were cultured and treated with different concentrations of bortezomib (1-500 nmol/L) for 24-48 h. Cell viability was determined by MTT assay. Apoptosis was detected by flow cytometry. The cleavage of PARP and caspase-3 and level of phosphor-Akt were determined by Western blot.

RESULTS: Bortezomib inhibited the viability of SGC7901 cells in a dose- and time-dependent manner. The IC₅₀ value at 48 h was 67.39 nmol/L. Treatment with 60 or 180 nmol/L of bortezomib induced cell cycle arrest at G₂/M phase at both 24 and 48 h but induced apoptosis only at 48 h. The cleavage of caspase-3 and PARP was observed in cells treated with 60 or 180 nmol/L of bortezomib for 48 h. Treatment with bortezomib for 48 h down-regulated the level of phosphor-Akt in SGC7901 cells.

CONCLUSION: Bortezomib induced apoptosis and cell cycle arrest at G₂/M phase by inhibiting the activity of the PI3K/Akt signaling pathway in human gastric cancer SGC7901 cells.