Cisplatin resistence and NPRL2 gene..
Abstract Number: 2340
Presentation Title: Activation of tumor suppressor NPRL2 facilitates cisplatin-mediated cell cycle arrest and apoptosis in DNA-damage checkpoint pathways in lung cancer
Presentation Start/End Time: Monday, Apr 03, 2006, 9:40 AM - 9:55 AM
Location: Room 150, Washington Convention Center
Author Block: Kentaro Ueda, Shoichiro Ohtani, John D. Minna, Jack A. Roth, Lin Ji. The University of Texas M.D. Anderson Cancer Center, Houston, TX, The University of Texas Southwestern Medical Center, Dallas, TX
NPRL2 is one of the candidate tumor suppressor genes residing on a 120-kb homozygous deletion region in human chromosome 3p21.3. We previously found that expression of endogenous NPRL2 correlates with cisplatin (CDDP) sensitivity in non-small cell lung cancer (NSCLC) cells, and re-expression of NPRL2 in NPRL2-negative and CDDP-resistant cells effectively re-sensitizes these cells’ response to CDDP in vitro. The purpose of this study was to elucidate the molecular mechanisms involved in NPRL2-mediated sensitization of NSCLC cells to CDDP. We observed that compared with CDDP alone, NPRL2 nanoparticle plus CDDP at inhibitory concentration 20 (IC20) significantly facilitated CDDP-mediated cell cycle arrest at the G2/M phase and induced apoptosis (p < 0.05). We also found that forced expression of NPRL2 in NPRL2-negative and CDDP-resistant NSCLC cells effectively activated Chk2 and Chk1 kinases, inactivated key downstream negative regulatory components including Cdc25A and Cdc25C in cell cycle checkpoint pathways, and accelerated the formation of ?-H2AX, a phosphorylated form of the histone H2AX protein shown to be an important and early chromatin modification following initiation of DNA damage and DNA fragmentation during apoptosis. In addition, we detected substantial activation of caspases 2, 8, 9 and 3 in NSCLC cells transfected by NPRL2 nanoparticles plus CDDP at IC20 compared with NSCLC cells treated with either agent alone or with LacZ plus CDDP. Furthermore, we evaluated the effect of a combination treatment with systemic administration of NPRL2 nanoparticle and intraperitoneal injection of CDDP on tumor formation and growth in a human NSCLC H322 (NPRL2-negative and CDDP-resistant) orthotopic lung cancer mouse model with a quantitative noninvasive magnetic resonance imaging analysis. We found that this combination treatment significantly inhibited tumor formation and tumor growth compared with either agent alone or LacZ plus CDDP (p < 0.05). We also detected substantially enhanced accumulation of phospho-Chk2 and ?-H2AX by an immunofluorescence imaging analysis and induction of apoptosis with an in situ TUNEL staining in frozen tumor tissues of animals treated with NPRL2 nanoparticle plus CDDP. Our results suggest that NPRL2 can function as an important effector in facilitating DNA-damage-induced apoptosis by activation of multiple pro-apoptotic effectors and regulation of key components in DNA-damage-induced apoptosis and cell cycle checkpoint pathways and that treatment with NPRL2 nanoparticle plus CDDP may effectively overcome CDDP resistance in lung cancer cells. This abstract is supported by a grant from the NIH and NCI SPORE P50CA70907.
|
