IntroductionIn this article, we report 7 novel KRAS gene mutations discovered while retrospectively studying the prevalence and pattern of KRAS mutations in cancerous tissue obtained from 56 Saudi sporadic colorectal cancer patients from the Eastern Province.MethodsGenomic DNA was extracted from formalin-fixed, paraffin-embedded cancerous and noncancerous colorectal tissues. Successful and specific PCR products were then bi-directionally sequenced to detect exon 4 mutations while Mutector II Detection Kits were used for identifying mutations in codons 12, 13 and 61. The functional impact of the novel mutations was assessed using bioinformatics tools and molecular modeling.ResultsKRAS gene mutations were detected in the cancer tissue of 24 cases (42.85%). Of these, 11 had exon 4 mutations (19.64%). They harbored 8 different mutations all of which except two altered the KRAS protein amino acid sequence and all except one were novel as revealed by COSMIC database. The detected novel mutations were found to be somatic. One mutation is predicted to be benign. The remaining mutations are predicted to cause substantial changes in the protein structure. Of these, the Q150X nonsense mutation is the second truncating mutation to be reported in colorectal cancer in the literature.ConclusionsOur discovery of novel exon 4 KRAS mutations that are, so far, unique to Saudi colorectal cancer patients may be attributed to environmental factors and/or racial/ethnic variations due to genetic differences. Alternatively, it may be related to paucity of clinical studies on mutations other than those in codons 12, 13, 61 and 146. Further KRAS testing on a large number of patients of various ethnicities, particularly beyond the most common hotspot alleles in exons 2 and 3 is needed to assess the prevalence and explore the exact prognostic and predictive significance of the discovered novel mutations as well as their possible role in colorectal carcinogenesis.

background: There remains an unmet need to identify molecular biomarkers in ewing sarcoma (es). We sought to assess the influence of the O 6 -methylguanine-DNA methyltransferase (MGMT) promoter methylation on response and progression-free survival (pFs) following initiation of irinotecan and temozolomide (IT), pFs following initiation of vincristine, doxorubicin, and cyclophosphamide alternating with ifosfamide and etoposide (VDC-Ie), and overall survival (Os).Materials and methods: Data of advanced es patients, treated with IT were retrospectively collected. patients were required to have progression after prior VDC-Ie. MGMT promoter methylation was assessed on non-decalcified Formalin-fixed paraffin embedded (FFpe) tissue using methylation sensitive restriction enzyme-quantitative pCr (Msre-qpCr). survival was estimated by the Kaplan-Meier method.results: A total of 20 es patients underwent MGMT promoter methylation testing, and were eligible for analysis. Five patients (25%) had methylated MGMT, whereas the remaining (15; 75%) had unmethylated promoter. Five (25%) had objective response to IT, with no observed difference by promoter methylation (p = 0.76). Median pFs from initiation of IT for methylated vs. unmethylated MGMT patients was 4.9 and 1.2 months, respectively, p = 0.69. Median pFs from date of initiation of VDC-Ie was significantly superior in the methylated group; 27.8 vs. 8.6 months, p = 0.034. Median Os was superior but not statistically significant in the methylated group. conclusion: MGMT-promoter methylation did not correlate with clinical activity or outcomes following the IT regimen for advanced es. however, methylated MGMT predicted significantly superior pFs following initiation of the standard VDC-Ie protocol.

No abstract

No abstract