Analysis of gene expression in human colorectal cancer tissues by cDNA array

cDNA array analysis for prediction of hepatic metastasis of colorectal carcinoma

PURPOSE

Distant metastasis is a significant prognostic factor of colon carcinoma. Adjuvant chemotherapy has been shown to decrease its recurrence. However, there are no definitive methods for the diagnosis of hepatic recurrence after potentially curative surgery. The aim of this study was to evaluate the accuracy of mRNA expression profiling using samples obtained from primary tumors to predict hepatic recurrence.

METHODS

Patients with stage III colorectal carcinoma without any recurrence for at least 5 years (group A: n = 9) and patients with stage IV carcinoma with hepatic metastasis (group B: n = 10) were included in this study. Tissue samples were collected from the primary tumor and adjacent normal colonic mucosa at the time of surgery in each patient. Total RNA was extracted and the mRNA expression profile was examined using a cDNA macroarray.

RESULTS

A hierarchical clustering analysis revealed a dendrogram in which the patients were divided into two clusters. One cluster consisted of seven patients in group A and two in group B. The other consisted of two patients in group A and eight in group B. Therefore, the positive and negative predictive value of hierarchical clustering analysis for hepatic metastasis was 80.0% and 78.8%, respectively. Fifteen genes were revealed to be upregulated and 12 were downregulated in group B. The upregulated genes included CCNA2, TP53, and MDM2, while the downregulated genes included CDH1, GADD45A, and BCL2L2.

CONCLUSIONS

mRNA expression profiling by a cDNA array analysis of specimens obtained from primary tumors was found to be useful for distinguishing patients with and without hepatic metastasis. This method is expected to contribute to the identification of patients at high risk for hepatic recurrence, while also helping in the administration of intensive adjuvant chemotherapy for such high risk patients.

A case of colorectal carcinoma in adenoma analyzed by a cDNA array

PATIENT AND METHODS

A 68-year-old woman presenting with bloody stools and anemia was referred to our hospital. Colonoscopy showed a Is-type tumor of 45 mm in diameter in the cecum and three Is-type tumors in the ascending colon. Ileocecal resection with regional lymph node dissection was performed. Microscopically, the large tumor consisted of a well-differentiated adenocarcinoma with a tubulovillous adenoma (TVA) component (carcinoma in adenoma). Some carcinoma (CA) cells had invaded the submucosal layer, but the lymph nodes were negative for malignancy. The other three polyps were diagnosed as TVAs. Because her family history fulfilled the Amsterdam criteria II for hereditary non-polyposis colorectal cancer (HNPCC), genetic analysis was performed. All of the four tumor tissues were classified as microsatellite stable (MSS) according to the National Cancer Institute guideline for analysis of microsatellite instability (MSI). K-ras mutation was detected in both CA and TVA lesions of the carcinoma in adenoma. To clarify relevant alterations of gene expression associated with adenoma-carcinoma progression, the gene expression profiles of these tumor tissues were analyzed by a cDNA array.

RESULTS

Although the gene expression profiles were similar, insulin-like growth factor-II (IGF-II) was expressed most differentially in CA and TVA tissues. The results were further substantiated by comparison of the gene expression profiles of CA and TVA lesions of the carcinoma in adenoma.

CONCLUSION

The results suggest that overexpression of IGF-II played an important role in the progression of adenoma to carcinoma in this patient.

Gene expression profiling of colorectal adenomas and early invasive carcinomas by cDNA array analysis

It is generally accepted that most colorectal carcinomas arise in pre-existing adenomas. Morphologically, colorectal adenomas can be divided into two groups, protruded type and flat type. The aim of this study was to clarify relevant alterations of gene expression associated with the early stage of colorectal carcinogenesis. Using cDNA array, we analysed the expression profiles of 550 cancer-related genes in 36 colorectal adenomas (18 flat-type and 18 protruded-type adenomas) and 14 early invasive carcinomas. Among the 550 genes, we chose 32 genes the average expression levels of which were at least three-fold up- or downregulated in tumour tissues compared with levels in matched normal tissues. A total of 13 and 19 genes were identified as up- and downregulated genes in tumour tissues, respectively. Among the upregulated genes, the average expression levels of E1AF, bone morphogenic protein (BMP)-4, insulin-like growth factor (IGF)-2, inducible nitric oxide synthase (iNOS), tissue inhibitors of metalloproteinase (TIMP)-1, Smad4, and nm23 in tumour tissues were over five times higher than those in matched normal tissues. Colorectal adenomas and early invasive carcinomas were divided into two major clusters by clustering analysis. Moreover, flat- and protruded-type adenomas were divided into two major clusters by clustering analysis. The expression profiles obtained by the cDNA array clearly indicate that colorectal adenomas and early invasive carcinomas have specific expression profiles. Likewise, the gene expression profiles of flat- and protruded-type adenomas are different. These results indicate that molecular classification of early colorectal tumours by a cDNA array is feasible.

Interplay of insulin-like growth factor-II, insulin-like growth factor-I, insulin-like growth factor-I receptor, COX-2, and matrix metalloproteinase-7, play key roles in the early stage of colorectal carcinogenesis

PURPOSE

The aim of this study was to characterize the relationship of insulin-like growth factor (IGF)-II expression with IGF-I, IGF-I receptor (IGF-IR), cyclooxygenase-2 (COX-2), and matrix metalloproteinase (MMP)-7 in early colorectal carcinogenesis.

EXPERIMENTAL DESIGN

With the semiquantitative reverse transcriptase-PCR, 90 human colorectal tumor tissues (63 adenomas and 27 submucosal pT1 cancers) were analyzed for IGF-II, IGF-IR, IGF-I, COX-2, and MMP-7 expression. Ninety-nine adenoma tissues and 60 pT1 cancer tissues were also analyzed immunohistochemically for IGF-II expression. Loss of imprinting of the IGF-II gene was analyzed. Paired carcinoma and adenoma tissues obtained from a carcinoma in adenoma lesion was analyzed by a cDNA array.

RESULTS

IGF-II mRNA expression was detected in 37.8% of the 90 colorectal tumor tissues. The frequency of IGF-II mRNA expression was significantly higher in pT1 cancer (70.4%) than in adenoma (23.8%). Immunohistochemical IGF-II expression was also more frequently detected in pT1 cancer (58.3%) than in adenoma (25.3%). Loss of imprinting of the IGF-II gene was observed in 15 (44.1%) of the 34 colorectal tumors in which IGF-II was overexpressed. IGF-II expression was positively correlated with the expression of IGF-IR and IGF-I. COX-2 and MMP-7 mRNA expression was detected in 42.2% and 77.8% of the tumor tissues, respectively, and both were positively correlated with IGF-I, IGF-II, and IGF-IR expression. IGF-II was the most differentially expressed gene between carcinoma and adenoma lesions.

CONCLUSIONS

IGF-II, in conjunction with IGF-IR, IGF-I, COX-2, and MMP-7, seems to play a key role in the early stage of colorectal carcinogenesis.