Wnt signalling in adenomas of familial adenomatous polyposis patients.

BACKGROUND: Epigenetic silencing of Wnt antagonists and expression changes in genes associated with Wnt response pathways occur in early sporadic colorectal tumourigenesis, indicating that tumour cells are more sensitive to Wnt growth factors and respond differently. In this study, we have investigated whether similar changes occur in key markers of the Wnt response pathways in the genetic form of the disease, familial adenomatous polyposis (FAP). METHODS: We investigated epigenetic and expression changes using pyrosequencing and real-time RT-PCR in samples from seven patients without neoplasia, and matched normal and tumour tissues from 22 sporadic adenoma and 14 FAP patients. RESULTS: We found that 17 out of 24 (71%) FAP adenomas were hypermethylated at sFRP1, compared with 20 out of 22 (91%) of sporadic cases. This was reflected at the level of sFRP1 transcription, where 73% of FAP and 100% of sporadic cases were down-regulated. Increased expression levels of c-myc and FZD3 were less common in FAP (35 and 46% respectively) than sporadic tumours (78 and 67% respectively). CONCLUSION: Overall, the changes in expression and methylation were comparable, although the degree of change was generally lower in the FAP adenomas. Molecular heterogeneity between multiple adenomas from individual FAP patients may reflect different developmental fates for these premalignant tumours.

Pathological complete response with anti-PD-1 therapy in a patient with microsatellite instable high, BRAF mutant metastatic colon cancer: a case report and review of literature.

IMPORTANCE: Mismatch repair (MMR) and BRAF mutation status are established independent prognostic factors for colorectal cancer (CRC). MMR deficient tumors are considered to have better prognosis whereas BRAF mutation is associated with poor prognosis. Studies evaluating the combined effect of BRAF and MMR status suggest MSI-high and BRAF mutant patients have a poorer prognosis as compared to MSI-high and BRAF wild type patients. Emerging evidence suggests MMR status predicts the immune response to anti-PD-1 therapy in CRC patients; however little is known about combined MMR and BRAF mutation status in this context. Therefore, it is important to identify whether there is a differential response to anti-PD-1 therapy based on BRAF status in the subset of MSI-high CRC patients. OBSERVATIONS: We report the first case of MSI-high, BRAF mutant metastatic CRC that had an excellent response (pathologic complete response) to anti-PD-1 therapy. We take this opportunity to review the similar cases in literature and discuss combined MMR and BRAF status as a potential biomarker for anti-PD-1 therapy. CONCLUSION AND RELEVANCE: The case presented illustrates that anti-PD-1 therapy can be effectively used to treat CRC patients with MSI-high and BRAF mutant status which is usually considered a poor prognostic category as opposed to MSI-high and BRAF wild type tumors. Future studies with anti-PD-1 therapy distinguishing these molecular subgroups will improve our knowledge of whether BRAF status can add to MMR status as a predictive biomarker for anti-PD-1 therapy in patients with metastatic CRC.