Ras-Related Small GTPases RalA and RalB Regulate Cellular Survival After Ionizing Radiation

Journal Article · Wed Sep 01 04:00:00 EDT 2010 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/j.ijrobp.2010.03.023· OSTI ID:21451148

Kidd, Ambrose R; Snider, Jared L ^[1]; Martin, Timothy D ^[2]; Graboski, Sarah F ^[3]; Der, Channing J ^[1]

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1. Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (United States)
2. Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (United States)
3. Department of Radiation Oncology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (United States)

Purpose: Oncogenic activation of Ras renders cancer cells resistant to ionizing radiation (IR), but the mechanisms have not been fully characterized. The Ras-like small GTPases RalA and RalB are downstream effectors of Ras function and are critical for both tumor growth and survival. The Ral effector RalBP1/RLIP76 mediates survival of mice after whole-body irradiation, but the role of the Ral GTPases themselves in response to IR is unknown. We have investigated the role of RalA and RalB in cellular responses to IR. Methods and Materials: RalA, RalB, and their major effectors RalBP1 and Sec5 were knocked down by stable expression of short hairpin RNAs in the K-Ras-dependent pancreatic cancer-derived cell line MIA PaCa-2. Radiation responses were measured by standard clonogenic survival assays for reproductive survival, {gamma}H2AX expression for double-strand DNA breaks (DSBs), and poly(ADP-ribose)polymerase (PARP) cleavage for apoptosis. Results: Knockdown of K-Ras, RalA, or RalB reduced colony-forming ability post-IR, and knockdown of either Ral isoform decreased the rate of DSB repair post-IR. However, knockdown of RalB, but not RalA, increased cell death. Surprisingly, neither RalBP1 nor Sec5 suppression affected colony formation post-IR. Conclusions: Both RalA and RalB contribute to K-Ras-dependent IR resistance of MIA PaCa-2 cells. Sensitization due to suppressed Ral expression is likely due in part to decreased efficiency of DNA repair (RalA and RalB) and increased susceptibility to apoptosis (RalB). Ral-mediated radioresistance does not depend on either the RalBP1 or the exocyst complex, the two best-characterized Ral effectors, and instead may utilize an atypical or novel effector.

• OSTI ID: 21451148
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 1 Vol. 78; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMALS
APOPTOSIS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
BODY
COLONY FORMATION
DIGESTIVE SYSTEM
DISEASES
DNA REPAIR
ENDOCRINE GLANDS
EXTERNAL IRRADIATION
GLANDS
IONIZING RADIATIONS
IRRADIATION
MAMMALS
MICE
NEOPLASMS
ORGANS
PANCREAS
RADIATIONS
RADIOSENSITIVITY
REPAIR
RODENTS
SENSITIVITY
SURVIVAL CURVES
VERTEBRATES
WHOLE-BODY IRRADIATION