Several phase III clinical trials have validated the use of hyperthermia as an adjuvant to radiation therapy. Hyperthermia sensitizes mammalian cells to ionizing radiation. Therefore, the potential benefit of using heat in the clinic may be maximized if the molecular mechanisms for heat-radiosensitization are better understood. Radiation induces the formation of DNA double strand breaks (DSBs), and thermal radiosensitization is believed to be caused by an inhibition of repair of radiation-induced DSBs by heat. Normally, radiationinduced DSB repair is believed to occur via two pathways: non-homologous end-joining (NHEJ) and homologous recombination (HR). The Mre11 complex has been implicated to function in both of these pathways. Our preliminary data suggest that hyperthermia induces alterations to Mrell, RadSO and Nbsl, the proteins comprising the Mre11 complex. We have also shown that heat induces the translocation of these proteins from the nucleus to the cytoplasm. Heat-induced alterations to, or redistribution of the components of the Mre11 complex could result in a decrease in DSB repair efficiency and potentiation of radiationinduced cell killing. We will test the-hypothesis that heat-radiosensitization is caused by heat-induced alterations to, or redistribution of proteins of the Mre11 DSB repair complex. We will determine the role of Mre11 and Rad50 in heat-radiosensitization, and determine whether alterations of these proteins lead to an inhibition or decrease in the efficiency of DSB repair and heat-radiosensitization after cells are exposed to moderate temperature (41.5?C) hyperthermia treatments. Using Western blotting and confocal microscopy, we will characterize heat-induced thermal damage to, or relocalization of Mre11, RadSO, and Nbsl and attempt to identify the mechanisms by which these alterations occur. We will also determine the role of HR in heat-radiosensitization using silencing RNA (siRNA) targeting technology or conditional mutants deficient in specific NHEJ or HR proteins. ? ?

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA108582-03
Application #
7279131
Study Section
Radiation Therapeutics and Biology Study Section (RTB)
Program Officer
Wong, Rosemary S
Project Start
2005-09-01
Project End
2010-08-31
Budget Start
2007-09-01
Budget End
2010-08-31
Support Year
3
Fiscal Year
2007
Total Cost
$224,439
Indirect Cost
Name
Indiana University-Purdue University at Indianapolis
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
603007902
City
Indianapolis
State
IN
Country
United States
Zip Code
46202
Dynlacht, Joseph R; Batuello, Christopher N; Lopez, Jennifer T et al. (2011) Identification of Mre11 as a target for heat radiosensitization. Radiat Res 176:323-32
Gerashchenko, Bogdan I; Gooding, Gerirose; Dynlacht, Joseph R (2010) Hyperthermia alters the interaction of proteins of the Mre11 complex in irradiated cells. Cytometry A 77:940-52
Gerashchenko, Bogdan I; Dynlacht, Joseph R (2009) A tool for enhancement and scoring of DNA repair foci. Cytometry A 75:245-52
Batuello, Christopher N; Kelley, Mark R; Dynlacht, Joseph R (2009) Role of Ape1 and base excision repair in the radioresponse and heat-radiosensitization of HeLa Cells. Anticancer Res 29:1319-25