WILD-TYPE P53 AND P53 TEMPERATURE-SENSITIVE MUTANT SUPPRESS HUMAN SOFT-TISSUE SARCOMA BY ENHANCING CELL-CYCLE CONTROL

Soft-tissue sarcomas are a heterogeneous group of tumors that are puta tively mesenchymal in origin. Therapeutic advances in this disease hav e been limited over the past several decades. Approximately one-half o f all patients will ultimately succumb, usually to uncontrollable pulm onary metastases, Although little is known about the underlying molecu lar determinants driving soft-tissue sarcoma inception, proliferation, and metastasis, mutation of the p53 gene is the most frequently detec ted molecular alteration in this disease. Accordingly, we were interes ted in determining whether transduction of wild-type (wt) p53 into sof t-tissue sarcomas bearing mutated p53 genes might alter the malignant phenotype, SKLMS-1 is a human-derived leiomyosarcoma cell line with a codon 245 p53 point mutation. Cationic liposome was used to transfect wt p53 or 143Ala temperature-sensitive mutant p53 into this cell line. SKLMS-1 stable transfectants expressing wt p53 had decreased cell pro liferation in vitro, decreased in vitro colony formation in soft agar, and decreased tumorigenicity in severe combined immunodeficient mice in vivo. Flow cytometric analysis of cell cycle components demonstrate d markedly increased G(1) cell cycle arrest and decreased entry into S phase, which corresponded to the induction of p21(cip1) protein in th e transfectants, Using SKLMS-1 stable transfectants expressing the 143 Ala p53 temperature-sensitive mutant, we demonstrated the kinetics of and the causal relationship between wt p53 expression, the wt p53-depe ndent induction of cell cycle inhibitor p21(cip1), and inhibition of c ell cycle progression in p53-transfected SKLMS-1 cells. The ability to restore wt p53 growth-regulatory functions in soft-tissue sarcoma may ultimately be useful as a future therapy in patients with soft-tissue sarcomas.