Familial adenomatous polyposis: analysis of genetic instability of microsatellites Loci and genetic alternations of tumor suppressor genes

Sensitivity and polymorphism of Bethesda panel markers in Chinese population

PURPOSE

This study aims to analyze sensitivities and polymorphisms of the Bethesda panel markers (BAT25, BAT26, D2S123, D5S346 and D17S250) for microsatellite instability testing in Chinese from Jiangsu Province and their clinical implication.

METHODS

MSI, sensitivity and polymorphism analysis in 541 colorectal cancer (CRC) patients were detected by fragment analysis.

RESULTS

Five hundred and twenty-five tissue samples and 541 blood samples of the 541 sample pairs were successfully amplified. Thirty-four (6.5%) cases were MSI-high (MSI-H) while 33 (6.3%) and 458 (87.2%) were MSI-low (MSI-L) and microsatellite stable (MSS), respectively. BAT26 (85.3%) exhibited the highest instability followed by BAT25 (82.4%), D2S123 (67.6%), D17S250 (64.7%) and D5S346 (50.0%) in MSI-H cases. The median ages of CRC patients with LS, MSI-H, MSI-L and MSS status were 38-43, 48, 60 and 63, respectively. 75.0%, 44.1%, 12.1% and 7.0% CRC cases were mucinous carcinomas in LS, MSI-H, MSI-L and MSS group, respectively. For D2S123, D17S250 and D5S346, heterozygosity was 80.8%, 74.1% and 57.7% and sizes of polymorphic variation range (PVR) were 207bp to 234bp, 140bp to 169bp and 109bp to 137bp, respectively. For D2S123 and D5S346, there was a bimodal distribution distinguishing the D17S250 from an indistinct trimodal or tetramodal distribution.

CONCLUSION

MSI-H cases showed earlier onset and higher proportion of mucinous carcinomas. Mononucleotide BAT26 and BAT25 exhibited higher sensitivity than dinucleotides D2S123, D17S250 and D5S346 in the Chinese population. The dinucleotide markers were highly polymorphic with high percent of heterozygosity, great variation in repeat length and non-normal distribution in Chinese population from Jiangsu Province.

Tumor suppressor genes in familial adenomatous polyposis

Colorectal cancer (CRC) is mostly due to a series of genetic alterations that are being greatly under the influence of the environmental factors. These changes, mutational or epigenetic modifications at transcriptional forefront and/or post-transcriptional effects via miRNAs, include inactivation and the conversion of proto-oncogene to oncogenes, and/or inactivation of tumor suppressor genes (TSG). Here, a thorough review was carried out on the role of TSGs with the focus on the APC as the master regulator, mutated genes and mal-/dysfunctional pathways that lead to one type of hereditary form of the CRC; namely familial adenomatous polyposis (FAP). This review provides a venue towards defining candidate genes that can be used as new PCR-based markers for early diagnosis of FAP. In addition to diagnosis, defining the modes of genetic alterations will open door towards genome editing to either suppress the disease or reduce its progression during the course of action.

NM23 protein expression in colorectal carcinoma using TMA (tissue microarray): association with metastases and survival

CONTEXT

NM23, a metastasis suppressor gene, may be associated with prognosis in patients with colorectal carcinoma.

OBJECTIVE

To analyze NM23 expression and its association with the presence of lymph node and liver metastases and survival in patients operated on for colorectal carcinoma.

METHODS

One hundred thirty patients operated on for colorectal carcinoma were investigated. Tissue microarray blocks containing neoplastic tissue and tumor-adjacent non-neoplastic mucosa were obtained and analyzed by immunohistochemical staining using a monoclonal anti-NM23 antibody. Immunohistochemical expression was assessed using a semiquantitative scoring method, counting the percentage of stained cells. The results were compared regarding morphological and histological characteristics of the colorectal carcinoma, presence of lymph node and liver metastases, tumor staging, and patient survival. Statistical analysis was performed using the Mann-Whitney test, the Kruskal-Wallis test and Fisher's exact test. Survival analysis was performed using the Kaplan-Meier method and the log-rank test.

RESULTS

NM23 expression was higher in colorectal carcinoma tissue than in adjacent non-neoplastic mucosa (P<0.0001). NM23 protein expression did not correlate with degree of cell differentiation (P = 0.57), vascular invasion (P = 0.85), lymphatic invasion (P = 0.41), perineural infiltration (P = 0.46), staging (P = 0.19), lymph node metastases (P = 0.08), or liver metastases (P = 0.59). Disease-free survival showed significant association (P = 0.01) with the intensity of NM23 protein immunohistochemical expression in colorectal carcinoma tissue, whereas overall survival showed no association with NM23 protein expression (P = 0.13).

CONCLUSIONS

NM23 protein expression was higher in neoplastic colorectal carcinoma tissue than in adjacent non-neoplastic mucosa, showing no correlation with morphological aspects, presence of lymph node or liver metastases, colorectal carcinoma staging, or overall survival. Disease-free survival was higher in patients with increased NM23 expression.