Smoking is one of the leading risk factors that contribute to the development of head and neck squamous cell carcinoma (HNSCC). Smoking induces chromosome breaks. One of the most frequent and earliest alterations in HNSCC is the segmental loss of the short arm of chromosome 3 (3p). Another frequent observation is the activation of one of the most common fragile sites in HNSCC, FRA3B, which spans the FHIT gene, considered to be a tumor suppressor. Distal to FHIT is FANCD2, which encodes a protein required for the proper function of the Fanconi anemia/BRCA pathway and eventual repair of DNA damage through homologous recombination repair. Recently, it has been observed that FANCD2 gene and protein expression is decreased in HNSCC cells. Therefore, we hypothesize that 3p loss, resulting from the activation of the fragile site FRA3B, leads to FANCD2 gene copy loss and a defective DNA damage response. Western blots showed decreased expression of FHIT protein in HNSCC cell lines. Fluorescence in situ hybridization revealed partial loss of FANCD2 in HNSCC cell lines studied. Western blotting and quantitative RT-PCR showed decreased FANCD2 protein and gene expression in HNSCC cell lines with FANCD2 gene copy loss. HNSCC cell lines with decreased FHIT protein expression, FANCD2 gene copy loss, and decreased FANCD2 gene and protein expression exhibited decreased FANCD2 and RAD51 focus formation. Our results suggest that smoking could induce breakage of the fragile site, FRA3B, leading to FANCD2 loss and resulting in defective DNA damage repair. The use of targeted therapy on cancer cells with deficient DNA damage repair, like CHEK1 small molecule inhibitors, could improve the currently available cancer treatment schemes. The public health relevance of our studies involves the use of an abnormal FA/BRCA pathway as a marker for selective use of targeted cancer therapy for HNSCC.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-06092009-153339 |
| Date | 28 September 2009 |
| Creators | Flores Obando, Rafael Ernesto |
| Contributors | William S. Saunders, Ph.D., Robert E. Ferrell, Ph.D., Susanne M. Gollin, Ph.D. |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-06092009-153339/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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