Gene delivery of cyclin-dependent kinase inhibitors p21Waf1 and p27Kip1 suppresses proliferation of MCF-7 breast cancer cells in vitro

BACKGROUND

Because tumorigenesis depends on a variety of oncogenes, symphyseal study of combined genes may lead to more significant knowledge about tumorigenesis and progression. Combined deficiency of p21 and p27 proteins in mice is linked to more aggressive spontaneous tumorigenesis. We investigated the effect of the transfected p21 (Waf1) -p27 (Kip1) gene on centrosome duplication, cell proliferation, and apoptosis of MCF-7, a breast cancer cell line.

METHODS

The pIRES-p21 (Waf1) , pIRES-p27 (Kip1) , and pIRES-p21 (Waf1) -p27 (Kip1) genes were transfected into MCF-7 cells by lipofection. The effect on proliferation was evaluated by MTT assay and clone-formation assay. Cell cycle and apoptosis were analyzed by flow cytometry. Apoptosis was tested by flow cytometry and TUNEL assay. Centrosome duplication was detected by use of indirect immunofluorescence microscopy.

RESULTS

The results showed that the pIRES-p21 (Waf1) , pIRES-p27 (Kip1) , and pIRES-p21 (Waf1) -p27 (Kip1) significantly inhibited proliferation of MCF-7 cells, followed by accumulation of MCF-7 cells in cycle G1, induced apoptosis, and a decrease in the proportion of MCF-7 cells which contained abnormal centrosomes. Compared with p21 (Waf1) or p27 (Kip1) alone, combination of p21 (Waf1) and p27 (Kip1) had a much more significant effect (P < 0.05).

CONCLUSION

Altogether, these results indicate that the p21 (Waf1) -p27 (Kip1) gene combination has a more obvious antitumor effect than p21 (Waf1) or p27 (Kip1) alone. This study provides preclinical evidence that combination of p21 (Waf1) and p27 (Kip1) could be a novel and promising therapeutic approach to treatment of breast cancer with suppressed p21 (Waf1) and p27 (Kip1) expression.

Differential expression of forkhead box M1 and its downstream cyclin-dependent kinase inhibitors p27(kip1) and p21(waf1/cip1) in the diagnosis of pulmonary neuroendocrine tumours

AIMS

Pulmonary neuroendocrine (NE) tumours represent a spectrum of phenotypically distinct entities with different biological behaviours. Difficulties in classifying these tumours are frequently encountered in clinical practice. Forkhead box M1 (FoxM1) is essential for the development of various cancers and is a proliferation-specific transcription factor that regulates transcription of cell cycle genes, including cyclin-dependent kinase inhibitors p27(kip1) and p21(waf1/cip1) . This study was performed to determine the utility of FoxM1, p27(kip1) and p21(waf1/cip1) as immunomarkers for subtyping pulmonary NE tumours.

METHODS AND RESULTS

FoxM1, p27(kip1) and p21(waf1/cip1) expression was evaluated by immunohistochemistry in 60 pulmonary NE tumours [19 typical carcinoids (TCs), six atypical carcinoids (ACs), 17 large cell neuroendocrine carcinomas (LCNECs) and 18 small cell lung cancers (SCLCs)]. The frequencies of FoxM1 and p21(waf1/cip1) expression were significantly different between TCs and ACs (each P = 0.009), and those of FoxM1 and p27(kip1) expression were significantly different between LCNECs and SCLCs (P = 0.012 and P = 0.002, respectively). The combined FoxM1((-)) /p21(waf1/cip1(-)) and FoxM1((+)) /p27(kip1(high)) phenotypes had the best diagnostic accuracy for distinguishing TCs from ACs, and SCLCs from LCNECs, respectively.

CONCLUSIONS

FoxM1, p27(kip1) and p21(waf1/cip1) showed distinct immunoreactivity according to histological subtype, which may be of value as an ancillary test in the differential diagnosis of pulmonary NE tumours.