Role of detection of microsatellite instability in Chinese with hereditary nonpolyposis colorectal cancer or ordinary hereditary colorectal cancer

BAT-25 polymorphism in Chinese from Jiangsu province and its implication for locus microsatellite instability screening

Background

Colorectal cancer is one of the most common tumors with high mortality in China. Microsatellite instability (MSI) analysis is important for the diagnosis of hereditary non-polyposis colorectal cancer (HNPCC) and for the prediction of 5-FU chemotherapy efficiency of colorectal tumors, especially in terms of therapeutic response and overall survival rates. Among the MSI markers recommended by the NIH/NCI, BAT-25 has been extensively studied for its major role in MSI. BAT-25 presents different polymorphisms in different ethnic populations and studies of its polymorphisms in the Chinese population are still very limited.

Aims

To analyze the frequency of constitutive polymorphic variation at the BAT-25 locus in Chinese from Jiangsu Province and its implication for locus MSI screening.

Methods

The frequency of allelic variation at the BAT-25 locus of cervical cells from 500 healthy women and blood from 16 healthy males was assessed by direct sequencing. Twenty samples were also analyzed by fragment analysis. DNA extracted from blood of 94 patients with gastrointestinal cancer or endometrial cancer was analyzed by fragment analysis.

Results

After comparison with the sequencing results, the more frequent allele lengths were 126–127 bp, 128–129 bp, 129–130 bp, respectively consistent with the 24 poly(T) (T24), T25 and T26 alleles. At the BAT-25 locus, 516 healthy individuals had respectively 1.36%, 97.28% and 1.36% of the T24, T25 and T26. Whereas for the 94 cancer patients allelic frequencies were 0.53%, 1.06%, 96.8%, 1.6% for T15, T24, T25 and T26 alleles respectively. Sixteen healthy males had only the T25 allele and heterozygous T15 was only found in 1 male patient with colon cancer.

Conclusion

We established the relation between fragment length and thymine repeats in BAT-25. The results showed that the BAT-25 locus is quasimonomorphic in Chinese from Jiangsu province. Moreover we showed that variant alleles of BAT-25 were found more likely in blood from cancer patients than in healthy individuals, suggesting the need to perform comparative studies between tumor and blood, or normal tissue, as to obtain a correct MSI identification.

Comparative Polymorphism of BAT-26 between Healthy Individuals and Cancer Patients and Its Cancer Risk Implication for Local Chinese

Purpose

BAT-26 is one of the representative markers for microsatellite instability evaluation and presents different polymorphisms in different ethnic populations. The current knowledge of its comparative polymorphism between healthy individuals and cancer patients in the Chinese population is insufficient. This study aims to analyze germline polymorphic variations of BAT-26 between healthy individuals and cancer patients in Chinese from Jiangsu province and the associated cancer risk implications.

Methods

The various BAT-26 alleles and their percentages in cervical cells from 500 healthy women were assessed by direct sequencing. Twenty of these samples were also analyzed by fragment analysis. BAT-26 of blood DNA from 24 healthy individuals and 247 cancer patients was analyzed by fragment analysis.

Results

Compared with the sequencing results, 122.6-122.9 bp, 123.4-123.8 bp and 124.1-124.8 bp corresponded to the A25, A26 and A27 alleles, respectively. The 524 healthy individuals showed 4.58%, 92.18% and 3.24% of A25, A26 and A27, respectively. The variant alleles A18, A24, A28, A29 and A32 were only found in cancer patients, accounting for 0.81%, 0.40%, 0.40%, 0.40% and 0.40%, respectively; the A25, A26 and A27 alleles in cancer patients accounted for 6.48%, 77.33% and 13.77%.

Conclusions

Healthy individuals had a stable BAT-26 profile within the quasimonomorphic variation range (QMVR), but cancer patients harbored variant alleles outside QMVR and showed a trend from quasimonomorph to polymonomorph, suggesting that variant alleles of BAT-26 in germline cells may be regarded as a potential marker of higher cancer risk in the Chinese population from Jiangsu province.

Expression of hMSH2, hMLH1, transforming growth factor β receptor type Ⅱ, matrix metalloproteinase-7, tissue inhibitor of metalloproteinase-2 and their correlations with the biological behaviors of hereditary nonpolyposis colorectal cancer

AIM: To investigate the correlation of hMSH2, hMLH1, transforming growth factor β receptor type Ⅱ (TβRⅡ), matrix metalloproteinase-7 (MMP-7) and tissue inhibitor of metalloprotei-nase-2 (TIMP-2) expression with the biological behaviours of human hereditary nonpolyposis colorectal cancer (HNPCC).

METHODS: Immunohistochemical staining was used to detect the expression of hMSH2, hMLH1, TβRⅡ, MMP-7 and TIMP-2 protein in 30 cases of sporadic colorectal cancer (SCRC), 30 cases of HNPCC and 8 cases of normal colorectal mucosa, and their corresponding clinical datas were studied retrospectively.

RESULTS: The positive rates of hMSH2, hMLH1, TβRⅡ, MMP-7 and TIMP-2 expression were significantly related to the depth of invasion and lymph node metastasis, but not to the sex of patients and the size or position of tumors. The positive rates of hMSH2, hMLH1, TβRⅡ, MMP-7 and TIMP-2 expression were remarkably different between SCRC and HNPCC (P < 0.05). The expression of hMSH2 had a positive correlation with hMLH1 (r = 0.835, P < 0.01); The expression of TβRⅡ had positive correlations with hMSH2 (r = 0.592, P < 0.01), hMLH1 (r = 0.472, P < 0.01) and MMP-7 (r = 0.735, P < 0.01), while the expression of MMP-7 had negative correlations with TβRⅡ(r = -0.582, P < 0.01), TIMP-2 (r = -0.421, P < 0.01) in HNPCC.

CONCLUSION: The mutations of hMSH2 and hMLH1 beget the inactivation of TβRⅡ in HNPCC, which induces down-regulated expression of MMP-7 and up-regulated expression of TIMP-2. This might be one reason for the special biological behaviours of HNPCC.

Expression of transforming growth factor β receptor Type Ⅱ, matrix metalloproteinase-7 and tissue inhibitor of metalloproteinase-2 and their roles in the invasion and metastasis of hereditary nonpolyposis colorectal cancer

AIM: To investigate the roles of transforming growth factor β receptor Type Ⅱ (TβRⅡ), matrix metalloproteinase-7 (MMP-7) and tissue inhibitor of metalloproteinase-2 (TIMP-2) expression in the invasion and metastasis of human hereditary nonpolyposis colorectal cancer (HNPCC).

METHODS: Immunohistochemical staining was used to detect the expressions of TβRⅡ, MMP-7 and TIMP-2 protein in 30 cases of sporadic colorectal cancer (sporadic CRC) and 30 cases of HNPCC, and their corresponding clinical data were analyzed retrospectively.

RESULTS: The positive rates of TβRⅡ, MMP-7 and TIMP-2 expression in HNPCC were 40.0%, 46.7% and 63.3% respectively, while in sporadic CRC, the rates were 73.3%, 86.7% and 20.0% respectively. The ratio of MMP-7(+~++) to TIMP-2(-) in sporadic CRC was higher while that of MMP-7(-) to TIMP-2(+~++) was lower significantly than that in HNPCC. TβRⅡ, MMP-7 and TIMP-2 expression were closely related to the depth of invasion and lymph node metastasis, but not to the sex of patients, tumor size and position. The positive rate of MMP-7 expression was significantly increased in tissues with extra-chorion invasion and metastasis, but the expression of TβRⅡ and TIMP-2 were markedly decreased (P < 0.05). In HNPCC and sporadic CRC, positive correlation was found between TβRⅡ and MMP-7 expression (r = 0.735, P = 0.000; r = 0.792, P = 0.000), while negative correlation existed between TIMP-2 and TβRⅡ expression (r = -0.582, P = 0.001; r = -0.394, P = 0.031) as well as between TIMP-2 and MMP-7 expression (r = -0.473, P = 0.008; r = -0.388, P = 0.034).

CONCLUSION: TβRⅡ, MMP-7 and TIMP-2 are differently expressed in HNPCC and sporadic CRC. The expression rates and intensities of TβRⅡ and MMP-7 are obviously higher in sporadic CRC than those in HNPCC, while the positive expression of TIMP-2 was a reverse situation. So the imbalance of MMP-7/TIMP-2 is increased in sporadic CRC. Down-regulated expression of MMP-7, TβRⅡ and up-regulated expression of TIMP-2 may play important roles in the invasion and metastasis of HNPCC.