Expression of cytokeratin 20 in the blood of patients with disseminated carcinoma of the pancreas, colon, stomach, and lung

Correlation between CK18 gene and gastric carcinoma micrometastasis

AIM: To explore the biological behavior of gastric carcinoma micrometastasis (MM) with a marker of cytokeratin 18 (CK18) and to evaluate the clinical stage of gastric carcinoma and its prognosis.

METHODS: Reverse transcription-polymerase chain reaction (RT-PCR) was used to examine the expression of CK18 mRNA in 298 lymph nodes from 35 patients with gastric carcinoma and 20 lymph nodes from 10 patients with chronic peptic ulcer and gastric perforation diagnosed by pathological examination and surgery. CK18 mRNA expression of peripheral blood from 54 patients with gastric carcinoma and 10 healthy people were also examined.

RESULTS: Expression of CK18 mRNA was not found in 10 patients with benign pathological changes. CK18 mRNA expression in gastric carcinoma tissues was strongly positive. In gastric carcinoma patients, pathological examination revealed that 99 of 298 (33.2%) lymph nodes were positive, while RT-PCR showed that 133 of 298 (44.6%) lymph nodes had expression of CK18 mRNA. The difference was significant (P < 0.05). Among the 199 negative lymph nodes identified by pathological examinations, 34 (17.1%) displayed positive expression of CK18 mRNA by RT-PCR. The positive expression of CK18 mRNA was associated with lymph node micrometastasis (LMM) of gastric carcinoma. CK18 mRNA was negatively expressed in all 10 healthy cases and positively expressed in 38.9% of 54 blood specimens from gastric carcinoma patients. The positive rate was not correlated with tumor invasion of gastric carcinoma, but was significantly associated with TNM stage, lymph node metastasis (P = 0.0290, P < 0.05) and tumor differentiation (P = 0.2956, P<0.05).

CONCLUSION: RT-PCR with CK18 mRNA as a molecular marker is highly sensitive and specific in detecting LMM of gastric carcinoma. It can benefit the diagnosis of MM and guide studies on biological behavior, clinical phase, and therapy as well as relapse monitoring.

Clinical application of gene detection in micrometastases of gastric cancer

AIM: To analyze feasibility of amplifying P53 gene by FQ-PCR in micrometastasis detection of gastric cancer.

METHODS: PCR and FQ-PCR were used to detect the peripheral blood carcinoma gene in the metastased group (n = 12) and non-metastased group (n = 18) of gastric cancer, to evaluate the correlation between gene expression and micrometastasis in gastric cancer and the sensitivity of PCR and FQ-PCR.

RESULTS: P53 expression rate was 58.3% (7/12) in the metastased group, and 11.1% (2/18) in the non-metastased group. There was significant difference between the two groups (P <0.01).

CONCLUSION: P53 may be an important marker of micro-metastasis. FQ-PCR can be used to detect micrometastases of gastric cancer for early diagnosis.

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.