Chromosome 18q deletion and Smad4 protein inactivation correlate with liver metastasis: a study matched for T- and N- classification

Abstract

Smad4 protein, whose gene is coded at chromosome 18q21.1, is an important tumour suppressor that mediates transforming growth factor-beta. It has been reported that inactivation of the Smad4 gene and allelic loss of chromosome 18q correlate with liver metastasis and poorer prognosis in colorectal cancers. Utilising a recently developed method of immunohistochemical staining for Smad4 protein, we focused on the specific impact of Smad4 protein expression on liver metastasis in colorectal cancer. We also evaluated the association between chromosome18q deletion and liver metastasis. We selected 20 colorectal cancers with liver metastasis for the experimental group, and 20 cases without liver metastasis for the control. In order to exclude the influence of lymph node metastasis, all cases were lymph node negative. In addition, the two groups were matched for tumour depth, tumour differentiation and tumour location. We compared the expression level of Smad4 protein immunohistochemically in these 20 matched pairs. We also compared the loss of heterozygosity status at chromosome 18q in these 20 matched pairs. Immunohistochemical staining revealed a significant difference (P ¼ 0.024) in the level of Smad4 protein between the two groups. We also observed a significantly different (P ¼ 0.0054) ratio of allelic deletion at chromosome 18q21. Smad4 protein expression level and allelic loss at 18q21 are associated with the process of liver metastasis in colorectal cancers evaluated when excluding clinical and pathological features except for liver metastasis. (Vogelstein et al, 1988(Vogelstein et al, , 1989Benhattar et al, 1993;Kinzler and Vogelstein, 1996;Span et al, 1996;Kambara et al, 2004;Nassif et al, 2004). Loss of heterozygosity (LOH) is one of the major types of genetic inactivation, and the long arm of chromosome 18 is the most frequently deleted region in colorectal cancers. To date, many reports suggest that this deletion is a molecular predictor that affects survival (Fearon et al, 1990;Jen et al, 1994;Chung, 1998;Lanza et al, 1998;Ogunbiyi et al, 1998;Jernvall et al, 1999;McLeod and Murray, 1999;Sarli et al, 2004). We too reported that the allelic deletion of chromosome 18q was associated with poorer prognosis in stage III colon cancer after adjuvant chemotherapy (Watanabe et al, 2001. These reports suggest that there might be tumour suppressor genes located at chromosome 18q, which has a strong influence on survival. Smad4 gene, which mediates the intracellular signalling pathway of transforming growth factor (TGF)-beta receptor, has been detected as one of the target genes at 18q21 (Wang et al, 1995;Eppert et al, 1996;Hahn et al, 1996;Thiagalingam et al, 1996;Carethers et al, 1998;Markowitz, 2000;Fink et al, 2003;Alazzouzi et al, 2005;Li et al, 2005). Recently, an immunohistochemical method for evaluating Smad4 protein has been developed and several studies found higher frequency of Smad4 protein inactivation in the cases with liver metastasis and in the cases presenting unfavourable survival (Maitra et al, 20...

SMAD4 protein expression and cell proliferation in colorectal adenocarcinomas

“…SMAD4 alterations are not observed in precancerous lesions such as adenomas [23,37] and occur in approximately 5% of non-invasive epithelial colorectal lesions [8,37]. When considering invasive adenocarcinomas, SMAD4 mutations are more frequent and correlate with an advanced, metastatic tumour stage [8,23,30,[36][37][38]. Additional support for this relationship could be derived from data showing significant correlations between loss of immunohistochemical SMAD4 tumour expression or loss of 18q heterozygosity and lymph node [31,39], liver or distant metastases [23,30,31,36,39,40].…”

“…When considering invasive adenocarcinomas, SMAD4 mutations are more frequent and correlate with an advanced, metastatic tumour stage [8,23,30,[36][37][38]. Additional support for this relationship could be derived from data showing significant correlations between loss of immunohistochemical SMAD4 tumour expression or loss of 18q heterozygosity and lymph node [31,39], liver or distant metastases [23,30,31,36,39,40]. The results of our study suggest that aggressive disease, characterized by the presence of lymph node metastases, correlated with the loss of SMAD4 nuclear expression, which is in agreement with a metastasis promoter effect observed in colon cancer models [41,42].…”

“…In the present study, we investigated a 'homogeneous' group of invasive adenocarcinomas. Only SMAD4 nuclear staining was considered because current data are contradictory in terms of whether cytoplasmic staining and low staining intensity is an accurate reflection of gene status [33] or of signal transduction [32,[34][35][36]. Immunohistochemistry allows analysis of a large number of tumours and thus robust statistical analyses.…”

DPC4 Gene Status of the Primary Carcinoma Correlates With Patterns of Failure in Patients With Pancreatic Cancer

“…26 While these findings do not establish that Dpc4 plays a direct role in metastatic ability, an intriguing study by Michor et al 27 who applied mathematical modeling to the dynamics of metastasis suppressor gene inactivation found, at a constant rate of cancer cell dissemination, a striking similarity among bi-allelic advantageous mutations in a primary carcinoma and the expected number of metastatic foci (none to Ͼ 1,000) that paralleled the metastatic burden seen in this cohort of patients. While more studies are needed to clarify the role of DPC4 and other molecular features of pancreatic cancers in relation to patterns of failure (locally destructive v distant metastasis), our observations do indicate that fundamental molecular differences exist in a primary pancreatic carcinoma that underlies aggressive behavior or may influence response to treatment.…”

Colitic Cancer Develops Through Mutational Alteration Distinct from that in Sporadic Colorectal Cancer: A Comparative Analysis of Mutational Rates at Each Step

“…Further accumulation of genetic changes confers invasiveness or metastatic potential on the tumor (6, 7), and to date, several indicators have been identified to predict outcomes (7,8). In contrast, colitic cancer, which develops through inflammation-prone carcinogenesis in patients with ulcerative colitis (UC), has a somewhat different etiology (9).…”