Expression of MAC30 protein is related to survival and biological variables in primary and metastatic colorectal cancers

MAC30 is highly expressed in several types of tumors including colorectal cancers, however, its clinicopathological and biological significance in colorectal cancers is currently not known. The aim of our study was to investigate MAC30 expression in distant normal mucosa, adjacent normal mucosa, primary tumors and metastases of colorectal cancer, and to determine the relationship between MAC30 expression and clinicopathological and biological variables. MAC30 expression was immunohistochemically examined in distant normal mucosa (n = 54), adjacent normal mucosa (n = 123), primary tumors (n = 217) and lymph node metastases (n = 56) from colorectal cancer patients. MAC30 cytoplasmic expression was increased from distant normal mucosa to primary tumor and to metastasis (p < 0.0001-0.04). Furthermore, 40% primary and 37% metastatic tumors showed stronger cytoplasmic expression of MAC30 at the tumor invasive margins compared to inner tumor areas. Strong cytoplasmic expression of MAC30 in the metastasis was related to a poor prognosis (p = 0.04). MAC30 cytoplasmic expression was positively related to expression of proliferating cell nuclear antigen (p = 0.04), p53 (p = 0.04), nucleoporin 88 (p = 0.001), legumain (p = 0.004) and particularly interesting new cysteine-histidine rich protein (p = 0.004). However, MAC30 expression in the nucleus and stroma did not have any clinicopathological and biological significance (p > 0.05). In conclusion, MAC30 protein may play a role in development of colorectal cancer, and can be considered as a prognostic factor.     

Clinicopathological significance of Nup88 expression in patients with colorectal cancer

OBJECTIVE: The nucleoporin Nup88 is overexpressed in a series of human malignancies, however, its clinicopathological significance has not been studied. Our aims were to analyze Nup88 expression in normal mucosa, primary tumors and metastases from colorectal cancer patients and further to identify relationships of Nup88 expression with clinicopathological and other factors. MATERIALS AND METHODS: Using immunohistochemistry, we investigated Nup88 expression in 198 primary colorectal tumors, 96 normal mucosa samples and 35 lymph node metastases. RESULTS: The results showed that the intensity of Nup88 expression increased from the normal mucosa to the primary tumors (p < 0.0001) and tended to increase from the primary tumors to the metastases (p = 0.15). Both primary tumors and metastases presented stronger expression in the invasive margin and vascular-invaded areas. Nup88 expression was positively related to distal tumor location (p = 0.01), infiltrative growth pattern (p = 0.04) and higher proliferative activity (p = 0.04) and reversely to the grade of differentiation (p = 0.02) and apoptosis (p = 0.049). Strong expression of Nup88 predicted a worse outcome in the patients with distal tumors during the follow-up period of up to 3 years (p = 0.02). CONCLUSIONS: It seems that overexpression of Nup88 was involved in the tumorigenesis and aggressiveness of colorectal cancers, and Nup88 may be used as a prognostic factor in patients with distal tumors.     

p73 overexpression is a prognostic factor in patients with colorectal adenocarcinoma.

PURPOSE: To examine the expression of p73 in the different stages of colorectal cancer development and the association of p73 expression with patient survival. EXPERIMENTAL DESIGN: Expression of p73 protein was evaluated by immunohistochemistry in 221 primary colorectal cancer patients, including 58 patients with matched normal mucosa and metastases in the regional lymph nodes. RESULTS: Frequency and intensity of p73 expression were markedly increased from the normal samples (19%) to primary tumors (67%) and to metastases (95%). Overexpression of p73 predicted poor outcome in the whole group of patients (P = 0.014) and the subgroups with left-sided (P = 0.002) or ras-positive tumors (P = 0.019). The prognostic significance remained in the whole group (P = 0.008) and the subgroup with left-sided tumors (P = 0.019) after adjustment for the patient's sex, age, tumor stage, growth pattern, and differentiation. The p73 expression was positively correlated with ras expression (P = 0.006). The 5-year survival rates were 37, 53, 72, and 74% for the patients with p73+/ras+, p73+/ras-, p73-/ras+, and p73-/ras- tumors, respectively (P = 0.007). CONCLUSION: Our data indicate that overexpression of p73 independently predicted poor prognosis in the patients with colorectal cancer.     

Immunohistochemical dihydropyrimidine dehydrogenase expression is a good prognostic indicator for patients with Dukes' C colorectal cancer

BACKGROUND: Dihydropyrimidine dehydrogenase (DPD) is an enzyme that catabolizes 5-fluorouracil (5-FU), which is widely used for chemotherapy in patients with advanced colorectal cancer (CRC). However, the clinical importance of tumor dihydropyrimidine dehydrogenase (DPD) expression in patients with CRC treated with 5-FU remains unclear. MATERIALS AND METHODS: We investigated DPD activities in normal mucosa (N) and tumors (T) by enzyme-linked immunosorbent assay (ELISA) in 64 surgically resected patients with Dukes' C CRC who were treated orally with postoperative adjuvant FU-based chemotherapy. We also immunohistochemically investigated DPD expression in these specimens. The clinicopathological importance of DPD activity and expression was evaluated in the patients. RESULTS: Positive DPD expression was detected in 28 tumors (43.8%) and tumor DPD activity significantly correlated with tumor DPD immunoreactivity (p=0.0121). Further, tumor DPD activity and immunoreactivity also correlated with lymph node metastatic status (p=0.0409). The disease-free survival rate of patients with positive-tumor DPD expression was significantly worse than that of patients with negative-tumor DPD expression (39.3% vs. 72.2%, p=0.0127). However, DPD activity in tumors or normal mucosa did not correlate with patient prognosis. Tumor DPD expression appeared to be an important poor prognostic factor in patients with Dukes' C CRC by multivariate analysis (p=0.013). CONCLUSION: Immunohistochemical DPD expression in tumors is a useful prognostic parameter in patients with Dukes' C CRC treated with postoperative adjuvant FU-based chemotherapy.     

Overexpression of focal adhesion kinase in primary colorectal carcinomas and colorectal liver metastases: immunohistochemistry and real-time PCR analyses.

PURPOSE: Focal adhesion kinase (FAK), a protein tyrosine kinase that functions in signaling events between cells and their extracellular matrix, is overexpressed in a variety of human solid tumors. To determine whether FAK expression is up-regulated in colorectal cancer, we analyzed FAK mRNA and protein levels in primary colorectal tumors and colorectal liver metastases. EXPERIMENTAL DESIGN: p125(FAK) expression in formalin-fixed paraffin-embedded (FFPE) tissue was studied using immunohistochemical assays on 24 matched primary colorectal carcinomas and colorectal liver metastases as well as 18 different colorectal liver metastases using monoclonal anti-FAK 4.47. FAK mRNA expression was quantitated by real-time PCR on 39 matched normal colorectal mucosa and primary colorectal carcinomas as well as on 17 separate liver metastases. RESULTS: Elevated levels of p125(FAK) expression were demonstrated in both primary colorectal tumors and colorectal liver metastases compared with normal colorectal mucosa. Immunohistochemistry experiments demonstrated equivalent FAK expression in matched samples of colorectal primary tumors and liver metastases. Using real-time PCR in 39 matched samples, FAK mRNA copy number was significantly higher in primary colorectal tumors compared with normal colorectal mucosa. FAK expression was analyzed by both real-time PCR and immunohistochemistry in a separate set of colorectal liver metastases. Immunohistochemistry demonstrated high levels of FAK expression in 89% of samples. Furthermore, FAK mRNA copies in these unmatched liver metastases were significantly higher than the primary tumor FAK mRNA copies. CONCLUSION: These experiments have shown that both primary colorectal cancers and colorectal liver metastases express high levels of FAK mRNA and p125(FAK) protein. Furthermore, the majority of colorectal liver metastases demonstrated robust FAK expression equivalent to or greater than that in the primary colorectal tumor.     

Differences in messenger RNA expression of carcinoembryonic antigen in surgical specimens of colorectal carcinoma.

Carcinoembryonic antigen (CEA) is the most widely used tumor marker for colorectal cancer. Plasma CEA levels have been variably associated with prognosis. Since plasma CEA level is multifactorial, CEA gene expression in tumors may provide one precise mechanism to evaluate its functional role. This study evaluated CEA expression at the messenger RNA (mRNA) level in 22 human colorectal carcinomas and their adjacent normal mucosae by Northern blot hybridization using a 32P-labeled CEA probe (a loop-domain specific cDNA, LV7). Both tumor and normal mucosa displayed three mRNA species of 4.0, 3.6, and 3.0 kb in length. The expression of 3.6-kb mRNA which encodes for CEA was dominant and it was correlated with another 4.0-kb CEA mRNA expression. The expression of 3.0-kb mRNA which encodes for nonspecific cross-reacting antigen was weak and not detectable in 8 of 22 colon tumors and 12 of 22 normal colon mucosae. In only one tumor, a 4.5-kb mRNA (which might encode for a new family member of CEA) was expressed. A two- to fourfold higher expression of CEA mRNA (3.6 kb) was observed in 11 of 22 colorectal tumors (2 of 9 proximal colon tumors and 9 of 14 rectosigmoid tumors) when compared with morphologically normal adjacent mucosae. Preoperative plasma CEA levels and Dukes' staging had no correlation with this CEA mRNA expression. CEA mRNA did not appear to correlate with metastasis because its expression in the primary colon cancers with metastases (Dukes' stage D tumor) was not always increased. These data also imply that factors other than mRNA expression in tumor might be important in regulating plasma CEA levels.     

Determination of molecular marker expression can predict clinical outcome in colon carcinomas.

PURPOSE: Conventional staging procedures are often unable to precisely predict prognosis in colorectal cancer (CRC). In this study, we set out to investigate the possible role of molecular/structural indicators involved in cell cycle regulation (p27 and p53), apoptosis (p53 and p27), and tumor neoangiogenesis [p53, vascular endothelial growth factor (VEGF), and microvessel count] in predicting tumor behavior and clinical outcome in CRC patients EXPERIMENTAL DESIGN: Analysis of the above indicators was performed by immunohistochemistry on 104 CRC patient samples and 25 normal colon mucosa specimens. RESULTS: Intense p27 nuclear staining was found in normal colon mucosa, with p53 nuclear staining and VEGF cytoplasmic accumulation <10%, and low microvessel count. In contrast, in CRC samples, p27 was down-regulated in 53.8%, p53 protein was overexpressed in 52%, and VEGF stained positive in 67.3% of the cases, respectively. Multiple regression analysis showed that molecular markers were strongly correlated. In patients treated with curative surgery, a significant relationship was seen between p27 down-regulation and Dukes' stage, nodal status, and the presence of distant metastases. VEGF overexpression correlated significantly with Dukes' stage, tumor (t) and metastasis (m) parameters, and left site. Stepwise regression selected p27, p53, VEGF, and Dukes' stage as the best combination of variables capable of predicting both disease-specific and disease-free survival. CONCLUSIONS: The investigated indicators may be useful for the prediction of outcome and recurrence rate in curatively treated CRC patients. In conjunction with clinical and pathological staging, they may provide a stronger indication of clinical outcome than staging alone and help better select therapeutic options in CRC patients.     

Immunohistochemically detected thymidylate synthase in colorectal cancer: an independent prognostic factor of survival.

Intratumoral thymidylate synthase (TS) expression and M(r) 53,000 phosphoprotein (p53) overexpression were studied immunohistochemically in sections from stored paraffin-embedded primary colorectal cancers in 70 patients who had undergone surgery during the years 1987-1990. These cancers were classified according to Dukes' stage A-D, using monoclonal antibodies TS 106 and DO-7. In patients with Dukes' stage A-C tumors, univariate analyses showed that there was a significant correlation (P = 0.048) between disease-free survival and TS expression and between TS expression and time to death with colorectal cancer (P = 0.038). In patients with Dukes' stage A-D tumors, overall survival was correlated to TS expression (P = 0.015), Dukes' stage (P < 0.001), and level of tumor differentiation (P = 0.044) but not to p53 overexpression. Patients with low intratumoral TS expression survived significantly longer than patients with high expression. Cox multivariate analysis showed that Dukes' stage (P < 0.001) and TS expression (P = 0.043) could independently serve as prognostic factors for time to death with colorectal cancer in patients with Dukes' stage A-D tumors.     

Prognostic significance of the deleted in colorectal cancer gene protein expression in high-risk resected gastric carcinoma

The deleted in colorectal cancer (DCC) gene is a candidate tumor suppressor gene that may be associated with differentiation and proliferation of normal cells. Loss of heterozygosity (LOH) of 18q, where the gene is located, and absence of DCC protein expression have been associated with worse prognosis in certain subgroups of patients with colorectal adenocarcinoma. We studied the prognostic significance of loss-of-protein expression in 66 patients with resected gastric cancer with a high probability of relapse (T3, T4, N+). The DCC protein was detected with immunohistochemistry using an anti-DCC monoclonal antibody on paraffin-embedded sections. The DCC protein expression was present in 51 cases (77.3%) and absent in 15 cases (22.7%). Poorly differentiated and signet ring carcinomas had significantly lower expression than more differentiated tumors (p < 0.05) as did diffuse-type tumors compared to intestinal and mixed (p < 0.01). There was no correlation with proliferation rate, estimated immunohistochemically using an anti-proliferating cell nuclear antigen (PCNA) monoclonal antibody. Absence of DCC protein was an independent favorable prognostic factor (median survival 57 months vs. 18 months, p = 0.0176). The DCC protein expression was correlated with relapse site: all patients with distant metastases were positive for DCC staining, while one-third of patients with local/peritoneal relapse were negative (p < 0.01). In conclusion, DCC protein expression seems to be a significant prognostic factor in high-risk resected gastric cancer. Our results support previous data associating the DCC gene with differentiation and indicate that this gene may play a role in the metastatic potential of these tumors. These findings need to be confirmed by future larger studies.     

Cyclin B1, unlike cyclin G1, increases significantly during colorectal carcinogenesis and during later metastasis to lymph nodes

In collaboration with p53, cyclins B1 and G1 regulate the G2/M transition, a key checkpoint in the active cell cycle, which can be monitored by Ki67. However, the cyclin B1 expression remains unclear during colorectal carcinogenesis and during later metastasis to lymph nodes, and cyclin G1 expression is not clear in colorectal tumors. To clarify the variations of the two cyclins in colorectal tumors, cyclin B1, cyclin G1, p53, and Ki67 were immunohistochemically stained in 22 normal mucosa, 62 adenomas, 17 carcinomas in adenomas, 194 primary carcinomas, and 21 lymph node metastases; and the two cyclins were examined by Western blot in other 10 pairs of normal mucosa and primary carcinomas. Located in cytoplasms, nuclei or both, cyclin B1 expression increased significantly from normal mucosa through adenomas to primary carcinomas, from adenomas with mild dysplasia through those with moderate to those with severe, from peripheral adenomas to their central carcinomas, and from primary to metastatic foci. These increased expressions were confirmed by Western blot. Cyclin B1 expression, however, declined significantly in primary carcinomas showing large size, mucinous type, deep invasion, or short postoperative-patient-survival time. High cyclin B1 was linked to high p53 in adenomas, and to high Ki67 in adenomas and primary carcinomas. In contrast, found limited to nuclei, cyclin G1 expression did not vary significantly from normal mucosa through to metastatic carcinomas, and was not associated with clinicopathological parameters, p53 or Ki67. The unchanged expressions were confirmed by Western blot. Thus, increased cyclin B1, but not cyclin G1, may promote colorectal carcinogenesis and later metastasis to lymph nodes.     

p73 Overexpression and angiogenesis in human colorectal carcinoma

BACKGROUND: Solid tumors requires neovascularization for growth and metastasis. Angiogenesis depends on the local balance between positive and negative effectors, the production of which can be regulated by oncogenes and tumor suppressor genes. The aim of this study was to investigate expression of p73, a gene homologous to the tumor suppressor gene p53, in colorectal cancer and its relationship to angiogenesis. METHODS: p73 expression was examined by immunohistochemistry and western blot analysis on 56 primary colon carcinomas with matched normal mucosas. Vascular endothelial growth factor (VEGF) and microvessels were highlighted using a monoclonal antibody specific to VEGF and von Willebrand factor (vWF). RESULTS: The immunoexpressions of p73 were significantly higher in the primary colorectal carcinomas than that in the matched normal mucosa (P < 0.001). Western blotting showed that 85% patients have a high level of p73 expression (more than double the normal level). A close association between p73 and VEGF expression level was observed (P = 0.016). Colorectal adenocarcinoma that expressed p73 showed significantly greater vascularity than p73-negative tumors (P = 0.012). However, no association between immunoexpression of p73 and tumor stage or differentiation was observed. CONCLUSION: These findings suggest a potential role of p73 in tumor angiogenesis.     

Expression of cell cycle control proteins in primary colorectal tumors does not always predict expression in lymph node metastases.

Analysis of tumor markers focuses on expression in primary tumors with the assumption that this is representative of metastatic tumor, against which treatment is targeted. Few studies have compared the expression of such markers in primary and secondary tumors. In this study, several key genes involved in cell cycle regulation were investigated in colorectal tumors and corresponding lymph node metastases. The cell cycle regulators p53, cyclin D1, p21, p27, retinoblastoma protein (Rb), and proliferating cell nuclear antigen (PCNA) were examined in a series of 42 paired samples of primary colorectal and secondary lymph node tumors by immunohistochemistry. Expression of p53, p27, and Rb was similar in virtually all paired samples (p53, 38 of 42; p27, 39 of 42; Rb, 40 of 42), indicating that the pattern of these proteins in colorectal tumors may be used to predict that in lymph node tumors. It also suggests a lack of direct involvement in the metastatic process. A lower concordance for p21 and cyclin D1 staining was observed between primary and secondary tumors (p21, 19 of 42; cyclin D1, 22 of 42). p21 expression was more often observed in primary colorectal cancers, whereas cyclin D1 expression was more frequently seen in lymph node metastases, in keeping with the contrasting roles of these proteins as a cell cycle inhibitor (p21) and activator (cyclin D1). The PCNA-labeling index was found to vary considerably in a number of cases, thus limiting the ability to predict expression of this protein in lymph node metastases from the primary tumor. In addition, PCNA-labeling indices between paired samples were neither consistently higher nor lower, suggesting that the proliferative capacity of tumor cells is not directly related to their ability to metastasize.     

Legumain expression in relation to clinicopathologic and biological variables in colorectal cancer.

PURPOSE: Legumain, a novel asparaginyl endopeptidase, has been observed to be highly expressed in several types of tumors including colorectal cancer. However, there is no study examining the relationship of legumain expression to clinocopathologic and biological variables in colorectal cancers. EXPERIMENTAL DESIGN: We investigated legumain expression in 164 primary colorectal cancers, 34 corresponding distant normal mucosa samples, 89 adjacent normal mucosa samples, and 33 lymph node metastases using immunohistochemistry. We also did Western blotting analysis on three additional colorectal cancers and three colonic cell lines. RESULTS: Legumain expression was increased in primary tumors compared with distant or adjacent normal mucosa (P < 0.05), but there was no significant change between primary tumors and metastases (P > 0.05). Legumain expression was positively related to poorer differentiation/mucinous carcinoma (P = 0.04), higher degree of necrosis (P = 0.03) and apoptosis (P < 0.0001), positive proliferating cell nuclear antigen (P < 0.0001) and p53 expression (P = 0.049), and had a positive tendency towards stromelysin 3 (P = 0.058) and PINCH positivity (P = 0.05). The patients with tumors that showed both weak and lower percentage of the legumain expression, either in tumor (P = 0.01) or in stroma (P = 0.04), had a better prognosis. CONCLUSIONS: The legumain expression may be involved in colorectal cancer development and have a prognostic value in the patients.     

Expression of the deleted in colorectal cancer gene is related to prognosis in DNA diploid and low proliferative colorectal adenocarcinoma.

PURPOSE: Whether or not the deleted in colorectal cancer (DCC) gene is implicated in metastases or in predicting prognosis in patients with colorectal cancer has not previously been substantiated. Our aims were to investigate DCC expression in primary colorectal cancers and in metastases to identify any prognostic significance. PATIENTS AND METHODS: DCC expression was examined immunohistochemically in 195 primary colorectal adenocarcinomas and in 23 paired primary tumors and lymph node metastases. DNA content and S-phase fraction were measured by flow cytometry. RESULTS: The absence of DCC expression was observed in 55 primary tumors (28%). DCC negativity was significantly related to poor prognosis in patients with DNA diploid tumors (P =.03) and those with a low S-phase fraction (< 5%, P =.02) but not in patients with nondiploid tumors or those with a higher S-phase fraction. Furthermore, DCC expression retained its prognostic significance in the diploid subgroup after adjusting for sex, age, site, stage, growth pattern, and differentiation (P =.01). DCC expression was similar in primary tumors and their metastases. CONCLUSION: The absence of DCC predicted a poor outcome in the patients with diploid tumors and those tumors with a low S-phase fraction. Immunohistochemistry may be considered as a practical test to assess prognosis in this subgroup of patients.     

Fas ligand expression is correlated with metastasis in colorectal carcinoma

The Fas/Fas ligand (FasL) system is one apoptotic pathway through which malignant tumors can evade immune surveillance. While FasL is expressed in malignant tumors, Fas is conversely downregulated to escape host immune attack, resulting in tumor invasion. The aim of the current study was to find out further clinicopathological significance of FasL expression in carcinoma of the colon and rectum. FasL expression was investigated using immunohistochemical staining in 143 consecutive patients with primary colorectal carcinomas. Seventy-nine carcinomas (55.2%) expressed FasL. The incidence of lymph node and distant metastases in carcinomas expressing FasL was significantly higher than in carcinomas that did not express FasL (p = 0.031 and p = 0.0003, respectively). Although univariate analysis showed that survival in patients with carcinomas expressing FasL was significantly poorer than that in patients with carcinomas without FasL expression (p = 0.001), only Dukes' stage was an independent prognosticator by multivariate analysis. FasL expression was found to be correlated with lymph node involvement and distant metastases in colorectal carcinoma.     

Folic acid mediated attenuation of loss of heterozygosity of DCC tumor suppressor gene in the colonic mucosa of patients with colorectal adenomas

Loss of heterozygosity (LOH) and/or inactivation of tumor suppressor genes are implicated in the initiation and progression of many malignancies, including colorectal cancer. Although accumulating evidence suggests a chemopreventive role for folate in colorectal cancer, regulatory mechanisms are poorly understood. The primary objective of the current investigation was to determine whether folic acid would prevent LOH of the three tumor suppressor genes, deleted in colorectal cancer (DCC), adenomatous polyposis coli (APC) and p53 in macroscopically normal appearing rectal mucosa of patients with adenomatous polyps. In addition, the effect of folic acid on rectal mucosal proliferation was determined. Twenty patients were randomized in a double-blind study to receive either folic acid 5mg once daily or identical placebo tablets for 1 year. Genomic DNA and total protein were extracted from the rectal mucosa at baseline and after 1 year of treatment and analyzed for LOH and protein levels of APC, DCC and p53 genes. In addition, paraffin-embedded mucosal specimens were analyzed for proliferating cell nuclear antigen (PCNA) immunoreactivity, as a measure of cellular proliferative activity. Folate supplementation prevented LOH of DCC gene in five out of five (100%) patients who demonstrated baseline heterozygosity, whereas two out of four (50%) placebo-treated patients with baseline heterozygosity demonstrated allelic loss. Mucosal protein levels of DCC were also reduced in 7 of 10 (70%) placebo-treated patients compared to only 2 of 10 (20%) of patients treated with folate. Levels increased, however, in eight and three patients in the folic acid and placebo groups, respectively (P<0.02). Folic acid caused no change in allelic status of either APC or p53 gene. Folate supplementation caused a small, but not statistically significant, 16% reduction in mucosal proliferation, whereas placebo treatment resulted in a 88% (P<0.05) increase in this parameter, when compared with the corresponding baseline values. Our results indicate that folic acid prevents an increase in proliferation and arrests LOH of DCC gene and also stabilizes its protein in normal appearing rectal mucosa of patients with colorectal adenomas. Taken together, our data suggest that one of the ways folate may exert its chemopreventive effect is by stabilizing certain tumor suppressor gene(s) and preventing further increases in proliferation.     

Assessment of K-ras, Smad4 and p53 gene alterations in colorectal metastases and their role in the metastatic process

To date there is no genetic marker that gives accurate information on the prognostic impact for patients with colorectal cancer. A particular clone, not detected in the tumor, could be responsible for the metastatic process. To overcome this problem, genetic alterations were analyzed in metastatic tissues from 58 patients who developed metastases after curative surgery for colorectal cancer. K-ras, p53 and Smad4 alterations were observed in respectively 38, 60 and 27% of the metastases. These frequencies are similar to the ones reported in primary colorectal tumors. Thus, these genetic alterations cannot be used as prognostic biomarkers in patients with colorectal cancer. The metastases were stratified into 3 groups, according to the metastatic localization. K-ras mutations were detected in respectively 75, 26 and 11% of the distant, peritoneal and liver metastases. Loss of Smad4 expression was observed more frequently in the liver (62%) than in other metastases (13%). These results suggest that the genetic changes of the tumor cells indicate the location of the metastases and thus, the route of metastatic spread.     

Correlation of Skp2 with carcinogenesis, invasion, metastasis, and prognosis in colorectal tumors

In colorectal tumors, S-phase kinase-associated protein 2 (Skp2) still has numerous important questions unanswered: its expression in adenomas, its correlation with key clinicopathological indices, its association with patient prognosis, its variation in lymph node metastases, and its association with many cell-cycle regulators. To answer these questions in colorectal tumors, Skp2, cyclin A, cyclin B1, cyclin E, CDK2, and Ki67 were immunohistochemically stained in 12 normal mucosa, 36 adenomas, 11 carcinomas in adenomas, 102 primary carcinomas, and 12 paired lymph node metastases; and Skp2 was examined by Western blot in 8 pairs of normal mucosa and carcinomas. Situated in nuclei, Skp2 expression significantly increased from normal mucosa through adenoma to primary carcinoma (p<0.0001), from mild through moderate to severe dysplasia in adenomas (p=0.038), from peripheral adenoma to paired central carcinoma (p=0.0033), and from primary carcinoma to lymph node metastasis (p=0.015), and these increases were confirmed by Western blot. Expression, however, relatively declined significantly in the primary carcinomas showing deep invasion (p=0.0113), lymph nodal metastases (p=0.0268), and poor prognosis for all (p=0.0104) or stage III patients (p=0.0119). High Skp2 was also significantly linked with elevated cyclin A, cyclin B1, cyclin E, CDK2 (in primary carcinomas only), and Ki67 in both adenomas and primary carcinomas. Thus, overexpression of Skp2 is associated with colorectal carcinogenesis and late metastasis to lymph nodes, whereas relative reduction of Skp2 is correlated with local invasion of primary carcinoma.     

Allelic losses associated with the metastatic potential of colorectal-carcinoma

The aim of this study was to define the association of allelic losses with the metastatic potential of colorectal carcinoma and to determine whether allelic losses can be genetic markers for the prognosis of patients with colorectal carcinoma. Eighty primary colorectal tumors and 31 liver metastases from 95 patients were examined for loss of heterozygosity (LOH) at the APC, p53, RB, DCC and chromosome 14q loci by using polymerase chain reaction-single strand conformation polymorphism analysis and restriction fragment length polymorphism analysis. The incidence of LOH at the DCC and RB loci and on chromosome 14q in liver metastases was significantly higher than that in primary tumors. DCC and RB alterations were detected more frequently in primary tumors with higher metastatic potential. Although no statistically significant association was found between these losses and survival or distant metastasis, patients with DCC losses showed poorer survival by multivariate analysis (p=0.056). Thus, inactivation of the DCC and RB genes and gene(s) on chromosome 14q seem to be critical genetic events for the acquisition of metastatic potential in colorectal carcinoma. However, further studies will be required to utilize these genetic alterations as valuable prognostic markers.