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

Journal Article · Wed Sep 01 00:00:00 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, Vol. 78, Issue 1; Other Information: DOI: 10.1016/j.ijrobp.2010.03.023; PII: S0360-3016(10)00458-X; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

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