Cisplatin resistance in lung cancer
Identification of genes involved in resistance of lung cancer cells to cisplatin
E. Siebring-van Olst1, R.X. de Menezes2, E.F. Smit1, V.W. van Beusechem3
Depts. of 1Pulmonary Diseases, 2Epidemiology and Biostatistics, and 3Medical Oncology, VU University Medical Center, Amsterdam (Stichting CCA / Walter Bruckerhoff Stiftung)
Lung cancer remains the major cause of cancer related deaths throughout the world. Therapeutic options are limited. Cisplatin, a DNA damaging agent, is the corner stone in the palliative treatment of advanced non small cell lung cancer (NSCLC). Unfortunately, 70% of the cancers in these patients is unresponsive. Responsive cancers develop resistance to cisplatin. Currently there are no agents to circumvent this resistance. In this project, we aim to identify genes involved in resistance of NSCLC cells to cisplatin by a functional genomics approach using RNAi technology, with emphasis on inhibition of DNA repair and restoring p53 tumor suppressor function. Previously, genome-wide siRNA screens on A549 NSCLC cells and validation experiments yielded 14 lead targets for reactivation of p53 in lung cancer. Currently, we are investigating the mechanism of p53 inhibition by several of these genes. This year, bioinformatic analysis of the screen results revealed 22 miRNAs possibly involved in p53 repression. Validation experiments with miRNA mimics confirmed that 7 miRNAs indeed modulated p53 activity in the screen cell line; three of which also modulated p53 activity in a second NSCLC cell line. Furthermore, we screened a large panel of siRNAs silencing p53 modulators and a random set control genes for their effect on cisplatin sensitivity. Many siRNAs were found that sensitized A549 cells to cisplatin. The 20 strongest sensitizers were selected for further research, which is currently ongoing.