Genetic detection of lymph node micrometastases in patients with gastric carcinoma by multiple-marker reverse transcriptase-polymerase chain reaction assay

Effect of lymph node micrometastases on prognosis of gastric carcinoma

AIM: To evaluate the relationship between lymph node micrometastases and prognosis of patients with gastric carcinoma and to evaluate the significance of the new assessment of nodal status in determining the pN categories in the 5th edition of the UICC TNM classification.

METHODS: A total of 850 lymph nodes from 30 patients with gastric carcinoma who underwent gastrectomy with lymphadenectomy were assessed by reverse transcription polymerase chain reaction assay in addition to histologic examination. Cytokeratin-20 gene marker was used in this assay.

RESULTS: Routine examination by HE staining confirmed metastasis in 233 lymph nodes from 20 patients. All these 233 lymph nodes were cytokeratin-20 positive. Moreover, lymph node micrometastases were detected in an additional 67 lymph nodes in 12 of these 20 patients. Lymph node micrometastases were also detected in 10 lymph nodes from 2 of 10 patients who had no obvious metastases identified by HE staining. Totally, lymph node micrometastases were identified by the reverse transcription polymerase chain reaction assay in 77 (12.5%) lymph nodes from 14 (46.7%) patients with gastric carcinoma. Of 27 patients who underwent curative resection, 7 (25.9%) were up-staged (fromIB stage to II stage in 1 patient, from IB stage to IIIA stage in 1 patient, from II stage to IIIA stage in 1 patient, from IIIA stage to IIIB stage in 1 patient, from IIIA stage to IV stage in 1 patient, from IIIB stage to IV stage in 2 patients). In a median follow-up of 32 (range 8-36) mo, Kaplan-Meier survival analysis showed significant improvements in median survival (22.86 ± 3.17 mo, 95% CI: 16.64-29.08 mo vs 18.00 ± 7.4 mo, 95% CI: 3.33-32.67 mo) of patients with negative lymph node micrometastases over patients with positive lymph node micrometastases (log-rank, P < 0.05).

CONCLUSION: Lymph node micrometastases have a significant impact on the current staging system of gastric carcinoma, and are significant risk factors for prognosis of patients with gastric carcinoma.

K-19 mRNA RT-PCR in detecting micrometastasis in regional lymph nodes of gastric cancer

AIM: To investigate the value and prospect of RT-PCR in detecting micrometastasis in regional lymph nodes of gastric cancer.

METHODS: Histopathology was used and K19 mRNA expression was detected by RT-PCR in tumor tissues and lymph nodes from gastric cancer patients undergoing radical resection of gastric carcinoma.

RESULTS: K19 mRNA was expressed in all tumor specimens of 30 cases; of the 126 lymph nodes, 26 were histopathologically positive (20.6%), and 42 positive (33.3%) by RT-PCR. Amplification fragments of 460 and 540 bp were shown in all the tumor tissues and metastatic lymph nodes after K19 and β-actin RT-PCR, while only a 540 bp fragment appeared in the lymph nodes of non-tumor patients.

CONCLUSION: K19 mRNA RT-PCR is sensitive and specific in testing micrometastasis in regional lymph nodes of gastric cancer, and it is superior to routine histopathology.

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Lymph node micrometastasis and its correlation with MMP-2 expression in gastric carcinoma

AIM: To examine matrix metalloproteinase-2 (MMP-2) expression in gastric cancer tissues and to evaluate its relationship with lymph node micrometastasis.

METHODS: The authors studied 850 lymph nodes resected from 30 patients with gastric carcinoma who underwent gastrectomy with lymphadenectomy using reverse transcription polymerase chain reaction (RT-PCR) assay in addition to H-E staining. MMP-2 expression of the tumor tissues was detected by immunohistochemical technique (EliVision^TM plus).

RESULTS: MMP-2 expression was positive in 21 (70%) cases and negative in 9 (30%) cases. No significant correlations were found between MMP-2 expression and other variables such as age, gender, tumor location, tumor diameter, Lauren classification and lymphatic invasion. In contrast, MMP-2 expression correlated significantly with depth of tumor infiltration (P = 0.022), lymph node metastasis (P = 0.030) and tumor differentiation (P = 0.043). Lymph node micrometastases were detected in 77 (12.5%) lymph nodes of 14 (46.7%) gastric carcinoma patients. MMP-2 expression was positive in 12 (85.7%) of the 14 patients with lymph node micrometastasis, and in 9 (56.3%) of the 16 patients without lymph node micrometastasis (P = 0.118).

CONCOUSION: Our results demonstrate that MMP-2 expression has significant correlation with tumor invasion, tumor differentiation and lymph node metastases. MMP-2 expression may be an important biological characteristics and significant prognostic parameter of gastric carcinoma. We also conclude that MMP-2 may participate in the development of lymph node micrometastasis of gastric carcinoma. Further investigations are needed to draw a conclusion.

Expression of E-cadherin in gastric carcinoma and its correlation with lymph node micrometastasis

AIM: To examine the expression of E-cadherin in the primary tumor and to evaluate its relationship with lymph node micrometastasis (LNM).

METHODS: The authors studied 850 lymph nodes resected from 30 patients with gastric carcinoma who underwent gastrectomy with lymphadenectomy using reverse transcription polymerase chain reaction (RT-PCR) assay in addition to H&E staining. Cytokeratin-20 (CK-20) gene marker was used in this assay. The level of E-cadherin expression in the primary tumor was examined by immunochemical technique (EliVision^TM plus).

RESULTS: LNM was detected in 77 (12.5%) lymph nodes of 14 patients (46.7%) with gastric carcinoma. The incidence of LNM was significantly higher in the diffuse type (12 of 19 cases, 63.2%) than in the intestinal type of gastric carcinoma (2 of 11 cases, 18.2%, P = 0.026). The incidence of LNM also increased in accordance with the depth of tumor invasion. The loss of expression of E-cadherin in primary tumors was found in 14 (46.7) of 30 tumors. The absence of E-cadherin expression was significantly associated with the Lauren classification (P = 0.026), lymph node metastasis (P = 0.011), the grade of differentiation (P = 0.004) and the lymphatic invasion (P = 0.001). Expression of E-cadherin was negative in 10 (71.4%) of the 14 patients with LNM, and in 4 (25%) of the 16 patients without LNM (P = 0.026).

CONCLUSION: The current results indicate that the RT-PCR assay is useful for the detection of LNM and can significantly increase the detection rate of lymph node metastasis in patients with gastric carcinoma. The Lauren classification and depth of tumor invasion are significantly associated with lymph node micrometastases. Our findings also indicate that E-cadherin may play an important role in determining the growth type and differentiation of gastric carcinoma. The loss of E-cadherin expression may contribute to LNM.

Detection of micrometastasis of gastric carcinoma in peripheral blood circulation

AIM: To detect the micrometastasis of gastric carcinoma in peripheral blood circulation using immunomagnetic beads sorting technique and RT-PCR technique, and to discuss its significance and the difference between the two methods.

METHODS: Density gradient centrifugation was used to isolate mononuclear cells from peripheral blood, immunomagnetic beads sorting technique and RT-PCR technique were used to detect the disseminated carcinoma cells. HE, immunocytochemical and immunofluorescence staining were also used to identify the characteristics of the cells separated with immunomagnetic beads sorting technique.

RESULTS: Cells expressing cytokeratin were separated and enriched from the peripheral blood specimens of patients suffering from gastric carcinoma or chronic gastritis. After HE staining, two kinds of cells with little cytoplasm were found. Majority of these cells had small and round nuclei, even chromatins and the thickness of nuclear membrane was normal. Immunohistochemical staining indicated that there were CD34 and CD45 expression on the cell membrane of this kind of cells and these cells also showed expressed human telomerase reverse transcriptase by immunofluorescence staining, but the expression of carcinoembryonic antigen was absent. So, these cells might hematopoiesis precursors. Another kind of cells had larger and abnormal nuclei with thicker nuclear membranes. Massed chromatins and poly-nucleoli were found in the nuclei. These cells expressed human telomerase reverse transcriptase and carcinoembryonic antigen, but CD34 and CD45 were not found on the cell membrane. So, these cells were considered as gastric carcinoma cells escaping from the original focuses and existing in the peripheral blood circulation. Carcinoma cells were found in 25 of 60(41.7%) specimens of peripheral blood from patients with gastric carcinoma, while there were no such cells separated from the blood specimens of chronic gastritis patients. The difference of positive rates of disseminated carcinoma cells between two groups was markedly significant (P < 0.005). The expressions of CK20 mRNA in peripheral blood specimens were examinated with RT-PCR. CK20 mRNA was detected from 32 of 60(53.3%) peripheral blood specimens in the group of gastric carcinoma patients, while none of the specimens from patients suffering from chronic gastritis had CK20 mRNA. Significant difference was also found between two groups (P < 0.005). Statistic analyses also showed that there was a significant difference between the positive rates of two methods in detecting the disseminated carcinoma cells from the peripheral blood circulation of gastric carcinoma patients (P < 0.05).

CONCLUSION: The results demonstrated that there were disseminated carcinoma cells in the peripheral blood circulation of some patients with gastric carcinoma. Disseminated carcinoma cells can be detected from the peripheral blood samples with immunomagnetic beads sorting technique and RT-PCR technique. The positive rate of RT-PCR technique is higher than that of immunomagnetic beads sorting technique in detecting micrometastasis.

Effect of P-selectin monoclonal antibody on metastasis of gastric cancer and immune function

AIM: To investigate the effect of cell adhesion molecule P-selectin monoclonal antibody (Mab) on metastasis and immune function of mice orthototopically implanted with human gastric cancer tissue.

METHODS: SCID mice were implanted orthotopically with SGC-7901 human gastric carcinoma tissue. Starting from day 3 after operation, animals were given intravenously PBS or P-selectin Mab (100 μg/injection) (for both normal mice and tumor-implanted mice with tumors), twice weekly for 3 wk. Two animals in each group were sacrificed randomly at the 1st, 2nd, 4th week and 6th week. While T cell and B cell transformation indices were determined with the ³H TdR infiltration method, the NK cell activity was detected by the LDH release method.

RESULTS: The metastatic rate in the P-selectin Mab treated group was lower than that in the PBS treated group (with tumors). The NK activity of normal mice increased over time. The immune functions (T, B cell function, NK activity) of the tumor group in the 6th week were significantly lower than those in the 4th week, but the change was attenuated by P-selectin Mab.

CONCLUSION: P-selectin Mab could suppress the metastasis of gastric cancer with no adverse effect on host immune function.