Antisense attenuation of p21 sensitizes kidney cancer to apoptosis in response to conventional DNA damaging chemotherapy associated with enhancement of phospho-p53.

PURPOSE: Kidney cancer is notoriously difficult to treat when metastatic due to its resistance to conventional chemotherapy. Thus, the 5-year survival rate in patients with metastatic renal cell carcinoma is less than 10% and novel approaches to treatment are needed. The cyclin kinase inhibitor p21 generally conveys an anti-apoptotic function through its induction by the DNA damage responsive p53 pathway. We capitalized on this function of p21 and used an antisense approach to sensitize p53-wt renal cell carcinoma cells to chemotherapy induced apoptosis by attenuating p21 protein levels.
MATERIALS AND METHODS: The human renal cell carcinoma cell lines ACHN and SN12C were transfected with antisense and control oligodeoxynucleotides. Assessment of p21 and apoptosis relevant protein levels as well as apoptosis was performed using standard techniques.
RESULTS: Pre-incubation of ACHN and SN12C cells with phosphorothioate antisense p21 oligodeoxynucleotide markedly attenuated p21 and sensitized cells to the apoptosis induced by doxorubicin and cisplatin, such that an order of magnitude less of doxorubicin or cisplatin could be used in the presence of antisense to achieve equivalent or greater cell death. In addition, the mechanism of ACHN cell death associated with p21 attenuation involved decreases in the levels of anti-apoptotic proteins as well as an increase in the active form of the pro-apoptotic protein p53.
CONCLUSIONS: Since phosphorothioate antisense oligodeoxynucleotides accumulate to a higher degree in the kidney and liver than in any other organ, our findings suggest a reevaluation of conventional chemotherapy in kidney cancer in association with antisense p21 oligodeoxynucleotide.