Progress 01/04/07 to 09/30/11
Outputs
OUTPUTS: The most tangible output of this work has been the increased interest by a number of different collaborators. For example, we are continuing the small molecule work in collaboration with Cyclacel Pharmaceuticals. I have also had collaborative discussions with Dr. Baldassera Stea, Head of Radiation Oncology, University of Arizona, and Dr. Sue Yom, Department of Radiation Oncology, University of California San Francisco, on potential clinical trials in the future. PARTICIPANTS: This project has provided funds to pay a portion of my technician's salary and provide significant stability to the completion of these publications. Collaborations have been established with radiation oncologists and a pharmaceutical company. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
1. Regulation of radiation-induced apoptosis following radiation. Previous studies demonstrated that apoptosis was present in the salivary glands following radiotherapy and a major focus of this project was to define the molecules responsible. a. Involvement of p53: We have determined that radiation-induced apoptosis in the parotid salivary gland increases with increasing dose of radiation. By using genetically modified mice, we were able to conclude that this apoptosis required the expression of p53. Furthermore, expression of p53 was required for the acute and chronic loss of salivary function following irradiation. These results indicated that apoptosis in the salivary glands following therapeutic head and neck irradiation is mediated by p53 and corresponds to salivary gland dysfunction in vivo. b. Translation to fractionated radiation regimen: During therapy, head and neck cancer patients are exposed to multiple rounds of radiation treatment which potentially increases the damage to the normal salivary gland. In our mouse model, we observed that treatment with fractionated radiation (1-2 Gy/day X 5 days) resulted in a significant level of apoptotic cells after each fraction with little difference between the different number of radiation treatments. Injections of recombinant IGF1 prior to each radiation treatment suppressed acute apoptosis and preserved salivary gland function following fractionated doses of radiation 30-90 days after treatment. These studies suggested that activation of IGF1 mediated pathways prior to head and neck radiation could have potential clinical relevance in modulating radiation-induced salivary gland dysfunction 2. Translating pre-clinical evidence to clinical trials. IGF1-mediated preservation and restoration of salivary gland function are extremely exciting findings and provide a translational model to study radiation-induced salivary gland dysfunction. a. Identifying small molecules to recapitulate IGF1: Due to potential adverse safety considerations, it is highly unlikely that a growth factor such as IGF1 would be utilized clinically to protect normal tissues during cancer therapy. Therefore it is a major objective of my laboratory to identify small molecule therapeutics that could replace IGF1. We are currently pursuing cdk inhibitors as candidate molecules that could represent a salivary specific mechanism to deal with radiation damage. These specific targeting molecules may provide a treatment option that alleviates the secondary side effects of radiotherapy without affecting tumor regression. b. Evaluation of tumor response to therapeutic interventions: An important consideration in any of our normal tissue protection studies is the affect on tumor treatment. We have utilized human head and neck squamous carcinoma cells to develop in vitro and in vivo responses to radiation in order to test our therapeutic interventions. Initial studies focusing on the effect of IGF1 revealed minimal affects on the radiation response of tumor cells. Once small molecules are identified that have the potential to replace IGF1, we intend to repeat these tumor studies as part of the pre-clinical validation.
Publications
- Limesand KH, JL Avila, K Victory, H-H Chang, YJ Shin, O Grundmann, and RR Klein (2010). IGF1 preserves salivary gland function following fractionated radiation, International Journal of Radiation Oncology, Biology, Physics, accepted. Available online 16 July 2010.
- Mitchell GC, JL Fillinger, S Sittadjody, JL Avila, R Burd, and KH Limesand (2010). IGF1 activates cell cycle arrest following irradiation by reducing binding of ΔNp63 to the p21 promoter. Cell Death and Disease, 1:e50; doi:10.1038/cddis.2010.28.
- Vissink A, JB Mitchell, BJ Baum, KH Limesand, SB Jensen, PC Fox, LS Elting, JA Langendijk, RP Coppes and ME Reyland (2010). Clinical management of salivary gland hypofunction and xerostomia in head and neck cancer patients: Successes and barriers. International Journal of Radiation Oncology, Biology, Physics, 15;78(4):983-91.
- Grundmann O, JL Fillinger, K Victory, R Burd and KH Limesand (2010). Restoration of radiation therapy-induced salivary gland dysfunction in mice by post therapy IGF1 administration. BMC Cancer, 10:417.
- Victory KR, R Burd, A Fribley, S Sittadjody, D Arnett, RR Klein, and KH Limesand (2010). Head and neck tumor cell radiation response occurs in the presence of IGF1. Journal of Dental Research, accepted
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Purpose: Radiotherapy for head and neck cancer consists of fractionated radiation treatments that cause significant damage to salivary glands leading to chronic salivary gland dysfunction with only limited prevention and treatment options currently available. Methods and materials: Mouse models were exposed to fractionated radiation and salivary gland function and histological analyses of structure, apoptosis, and proliferation were evaluated. Results: In this study, we report that treatment with clinically relevant fraction sizes of radiation results in a significant level of apoptotic cells in FVB mice after each fraction, which is significantly decreased in transgenic mice expressing a constitutively active mutant of Akt1 (myr-Akt1). Salivary gland function is significantly reduced in FVB mice exposed to fractionated radiation; however myr-Akt1 transgenic mice maintain salivary function under the same treatment conditions. Injection of recombinant IGF-1 into FVB mice, which activates endogenous Akt, suppresses acute apoptosis and preserves salivary gland function following fractionated doses of radiation 30-90 days after treatment. FVB mice exposed to fractionated radiation have significantly lower levels of PCNA positive salivary acinar cells 90 days after treatment which correlates with a chronic loss of function. In contrast, FVB mice injected with IGF-1 prior to each radiation exhibit acinar cell proliferation rates similar to untreated controls. Conclusion: These studies suggest that activation of IGF-1 mediated pathways prior to head and neck radiation could have potential clinical relevance in modulating radiation-induced salivary gland dysfunction and maintaining glandular homeostasis. PARTICIPANTS: The PI has conducted research experiments on this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Some therapies for radiation-induced xerostomia are designed to protect salivary glands during radiotherapy. Some are intended to provide temporary relief of symptoms. Others are aimed at restoring function to previously damaged glands. It is difficult to say any one of these approaches is better than another. Certainly, outright prevention is a lofty goal, but for more than 500,000 people in the U.S. who have undergone treatment for head and neck cancer, palliative and restorative therapies are equally important.
Publications
- No publications reported this period
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Overall these data from this Aim suggest that g-radiation-induced apoptosis plays a causal role in the reduction of salivary output and activation of Akt or suppression of p53 can preserve salivary function providing a potential treatment for the salivary glands in patients undergoing head and neck cancer treatment. These findings have been disseminated into open access journals to expand the readership audience. PARTICIPANTS: A post-doc Oliver Grundmann and a technician Jamia Fillinger have contributed to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Purpose: Radiation therapy for head and neck cancer causes adverse secondary side effects in the salivary glands and results in diminished quality of life for the patient. A previous in vivo study in parotid salivary glands demonstrated that targeted head and neck irradiation resulted in marked increases in phosphorylated p53 (serine18) and apoptosis, which was suppressed in transgenic mice expressing a constitutively active mutant of Akt1 (myr-Akt1). Materials and Methods: Transgenic and knockout mouse models were exposed to irradiation and p53-mediated transcription, apoptosis and salivary gland dysfunction were analyzed. Results: We report that the pro-apoptotic p53 target genes PUMA and Bax are induced in parotid salivary glands of mice at early time points following therapeutic radiation. This dose-dependent induction requires expression of p53 as no radiation-induced expression of PUMA and Bax is observed in p53 -/- mice. Radiation also induces apoptosis in the parotid gland in a dose dependent manner, which is p53-dependent. Furthermore, expression of p53 is required for the acute and chronic loss of salivary function following irradiation. In contrast, p53 -/- mice do not induce apoptosis and preserve salivary function after radiation exposure. Conclusion: These results indicate that apoptosis in the salivary glands following therapeutic head and neck irradiation is mediated by p53 and corresponds to salivary gland dysfunction in vivo.
Publications
- 1. Avila, J.L., O. Grundmann, R. Burd, K.H. Limesand (2008). Radiation-induced salivary gland dysfunction results from p53-dependent apoptosis. International Journal of Radiation Oncology, Biology, Physics, 73(2):523-9.
- 2. Grundmann, O, G. Mitchell, K.H. Limesand (2009). Sensitivity of salivary glands to radiation: From animal models to therapies. Journal of Dental Research, accepted.
- 3. K.H. Limesand, S. Said, and S.M. Anderson (2009). Suppression of radiation-induced salivary gland dysfunction by IGF1. PLoS One, accepted.
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Progress 01/01/07 to 12/31/07
Outputs
The objective of this proposal is to define the ability of Akt to maintain salivary gland function following fractionated doses of radiation. The long-term goal of this proposal is to evaluate whether IGF1 treatment of salivary glands prior to head and neck irradiation could activate Akt in situ and impact clinical therapeutics for salivary gland dysfunction and xerostomia. To date we have been working on several experiments within this proposal and are continuing to evaluate our clinical translational model. Preliminary results were disseminated via a departmental seminar to receive critical feedback which will influence future directions. Once experiments have been independently validated the results will be disseminated to a larger audience.
Impacts
Currently we have been able to demonstrate that an equal number of salivary acinar cells undergo apoptosis after each dose of radiation. Preliminarily this implies that our IGF1 injections need to be performed before each radiation treatment. We are currently evaluating if there are defects in the clearance of these apoptotic cells. We have also demonstrated that salivary function can be preserved in mice expressing activated Akt1 or injected with IGF1 following fractionated doses of radiation. This extends our previous studies which utilized a single dose of radiation. These data have provided a solid foundation that could lead to future clinical trials.
Publications
- No publications reported this period
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