Cisplatin-induced growth arrest of head and neck cancer cells correlates with increased expression of p16 and p53.
OBJECTIVE
To determine expression of cell cycle and apoptotic genes, biochemical analysis of CCL23 and antisense cyclin D1-transfected CCL23 (CCL23AS) cells in the presence of cisplatin was performed. In addition, biochemical analysis of CAL27 cells before and after treatment with cisplatin was performed to determine expression of cell cycle genes.


METHODS
CCL23, CCL23AS, and CAL27 cell lines were treated with cisplatin. Western blot analysis, fluorescence-activated cell sorting, and apoptosis assays were performed.


METHODS
In vitro study of head and neck cancer cell lines CCL23, CCL23AS, and CAL27.


METHODS
CCL23, CCL23AS, and CAL27 cells were treated with cisplatin.


METHODS
Expression of p16, p21, p53, Bcl-xL, Bcl-xS, p27, DP1, MDM2, Bcl-2, c-Jun, and Jun-D were assessed using Western blot analysis.


RESULTS
There was increased expression of p16, p21, p53, BCLxL, and BCLxS genes with cisplatin treatment in the CCL23 and CCL23AS cells. Expression of p27, DP1, MDM2, BCL2, c-iun, and jun-D remained unaltered after treatment. There was decreased phosphorylation of Rb protein with complete absence of hyperphosphorylated Rb in the maximally sensitized antisense cyclin D1-transfected (CCL23AS) cells. Fluorescence-activated cell sorter analysis revealed a decreased G2 phase of the cell cycle and an increased proportion of apoptotic cells in the CCL23AS cell line compared with parental CCL23 cells. Cell killing also occurred in the presence of caspase-3 inhibitor. While CCL23 cells contain wild-type p53, the CAL27 cells have a point mutation in codon 193 (A-->T transversion) of exon 6. However, CAL27 cells still exhibited increased expression of p21 after treatment with cisplatin.


CONCLUSIONS
These results, in combination with increased expression of the p53 downstream effecter p21, indicate that the cisplatin-induced cell cycle arrest operates through the p16/p53-dependent pathway, and a caspase-independent pathway may be involved. Combination treatment of head and neck squamous cell carcinoma via cell cycle inhibition and cisplatin holds promise as a potential therapy in the clinical setting.
Division of Head and Neck Surgery, University of California, Los Angeles, UCLA David Geffen School of Medicine, 90095-1624, USA.
Helena T
HT
Yip
Rajesh
R
Chopra
Rita
R
Chakrabarti
Mysore S
MS
Veena
Bharathi
B
Ramamurthy
Eri S
ES
Srivatsan
Marilene B
MB
Wang
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D053148:Caspase 3; D020169:Caspases / Q000032:analysis; D016923:Cell Death; D002945:Cisplatin / Q000494:pharmacology*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis*; D005434:Flow Cytometry; D006258:Head and Neck Neoplasms / Q000473:pathology*; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D016755:Proto-Oncogene Proteins c-jun / Q000032:analysis; D051736:Proto-Oncogene Proteins c-mdm2 / Q000032:analysis; D016160:Retinoblastoma Protein / Q000378:metabolism; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000032:analysis*; D051020:bcl-X Protein / Q000032:analysis
D000970:Antineoplastic Agents; C494811:BCL2L1 protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D018809:Proliferating Cell Nuclear Antigen; D016755:Proto-Oncogene Proteins c-jun; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D051020:bcl-X Protein; C413374:p27 antigen; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D002945:Cisplatin