Mitochondrial background. Recent studies on cancer have detected many mutations and much variability in the mitochondrial genome, particularly in the non-coding region (D-loop). The present study set out to sequence and examine the hypervariable region I (HVR-I) of the D-loop and transfer RNA Leucine (tRNA Leu) for mutations in breast cancer patients. Methods. Tumor and normal tissues from 17 patients that carry mutations in either BRCA1 (n = 11), BRCA2 (n = 3) or are non-carriers of mutations in either gene (n = 3) were examined by direct genomic sequencing of PCR products. Results. We found 44 variants in the HVR-I of 16 patients, twenty-six were polymorphisms, four somatic variants, and fourteen variations were undetermined because corresponding (unaffected) normal tissue was not available. One BRCA1 mutated tumor had four somatic tumor variants (1/14). All other BRCA1/BRCA2 mutated tumors had no somatic variants. Nine out of 14 (64%) of these patients had a total 22 germline variants. One out of three (33%) non-carriers had four germ-line variants. No variants were found in tRNA Leu. A five kilobase deletion was also found as a germ-line variant in two of seven (29%) patients. There were no obvious differences in the frequency of homoplasmic variants in the mitochondrial genome between the BRCA1/BRCA2 mutation carriers and non-carriers. Conclusion. Direct genomic sequencing of PCR products showed that there were no striking differences in homoplasmic variants between tumor and normal tissue, thus homoplasmic variants in mtDNA did not have a role in tumorigenesis in our samples. We speculate that the marked differences in mutation frequencies observed amongst various studies could be the result of differences in the techniques used to generate and analyze the data. / EGFR background. Recent studies have identified mutations in the tyrosine kinase (TK) domain of the epidermal growth factor receptor (EGFR) in lung carcinomas. These mutations make the tumors sensitive to a molecular targeted drug called getifinib. Methods. We also sequenced the TK domain of EGFR in 16 breast cancer patients (BRCA1 = 9, BRCA2 = 4, non-carriers = 3) for mutations. Results. We did not find mutations reported previously in lung carcinomas but we identified other variants, in exons 18, 20 and 21 of the mutation carvers. We found one out of thirteen (eight percent) of the BRCA1/BRCA2 mutation carriers had somatic tumor variants, three out of thirteen (23%) patients had somatic variants found only in the adjacent normal tissue, and four out of thirteen (31%) patients had germ-line variants. The non-carriers did not have any variants. The variants found in the exons were two missense variants in exon 18 of two patients, three 'silent' substitutions in exon 20 of three patients, and two patients had exon 21 variants; a missense variant and a 'silent' substitution. Intronic variants were also found in three patients. Patient 5420 harbored more than one variant in the tumor tissue and patient 5483 harbored more than one somatic variant in the adjacent normal tissue. Although the sample size is small, these preliminary results seem to show a difference in EGFR variants between BRCA1/BRCA2 mutation carriers and non-carriers. Conclusion . EGFR variants found in this study were not the same ones found in lung cancer, but other variants could be significant in breast cancer progression and could possibly represent drug targets for future therapy.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.98760 |
| Date | January 2005 |
| Creators | Makriyianni, Ioli. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Human Genetics.) |
| Rights | © Ioli Makriyianni, 2005 |
| Relation | alephsysno: 002327041, proquestno: AAIMR24732, Theses scanned by UMI/ProQuest. |
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