p53 gene mutations in early colorectal carcinoma. De novo vs. adenoma-carcinoma sequence

A genome-wide analysis of the molecular alterations occurring in the adenomatous and carcinomatous components of the same tumor based on the adenoma-carcinoma sequence

Identification of molecular alterations occurring in the adenomatous and carcinomatous components within the same tumor would greatly enhance understanding of the neoplastic progression of colorectal cancer. We examined somatic copy number alterations (SCNAs) and mRNA expression at the corresponding loci involved in the adenoma–carcinoma sequence in the isolated adenomatous and cancer glands of the same tumor in 15 cases of microsatellite‐stable “carcinoma in adenoma,” using genome‐wide SNP and global gene expression arrays. Multiple copy‐neutral loss of heterozygosity events were detected at 4q13.2, 15q15.1, and 14q24.3 in the adenomatous component and at 4q13.2, 15q15.1, and 14q24.3 in the carcinomatous component. There were significant differences in the copy number (CN) gain frequencies at 20q11.21–q13.33, 8q13.3, 8p23.1, and 8q21.2–q22.2 between the adenomatous and carcinomatous components. Finally, we found a high frequency of five genotypes involving CN gain with upregulated expression of the corresponding gene (RPS21, MIR3654, RSP20, SNORD54, or ASPH) in the carcinomatous component, whereas none of these genotypes were detected in the adenomatous component. This finding is interesting in that CN gain with upregulated gene expression may enhance gene function and play a crucial role in the progression of an adenoma into a carcinomatous lesion.

Immunohistochemical analysis of beta-catenin, E-cadherin and p53 in canine gastrointestinal epithelial tumors

Wnt/beta-catenin signaling, E-cadherin and p53 reportedly play important roles in the development and/or progression of human gastrointestinal cancer. The present study evaluated the roles of beta-catenin, E-cadherin and p53 in canine gastrointestinal tumors. Endoscopic biopsy or surgically resected samples, a total of 131, including 38 gastric, 13 small intestinal and 80 large intestinal tumors, were obtained from 95 dogs. Those specimens were examined pathologically. Immunohistochemically, nuclear beta-catenin expression was found in 88% (42/48) of polypoid type adenocarcinomas. Most cases of non-polypoid type adenocarcinomas lacked nuclear expression of beta-catenin with the exception of one case (6%, 1/17). Nuclear beta-catenin expression was not observed in signet ring cell carcinomas (0/15), mucinous adenocarcinomas (0/7) and undifferentiated carcinomas (0/4). The findings indicate that nuclear translocation of beta-catenin is closely related to the development of polypoid type adenocarcinomas but not that of non-polypoid type malignant tumors. The immunoreactivity of E-cadherin for tumor cells tended to decline overall in most of cases including benign tumors. Significant immunoreactivity for p53 was not found in 61% of tumors examined (80/131), including malignant tumors (63%, 57/91), while intense p53-immunoreactivity was rarely found in a few cases of malignant tumors (8%, 7/91). We could not conclude clearly significant correlations between histopathological tumor types and immunohistochemical results of E-cadherin or p53. This paper indicates the importance of the nuclear translocation of beta-catenin for the tumorigenesis of canine intestinal polypoid type adenocarcinomas, especially in the colorectum.

The impact of APC polymorphisms on the transition from polyps to colorectal cancer (CRC)

OBJECTIVE

The purpose of this study was to investigate the function of APC polymorphisms (D1822V and E1317Q) on the transition from polyps to colorectal cancer (CRC).

METHODS

259 patients with polyps were included in the study. APC polymorphisms were genotyped via polymerase chain reaction (PCR) and subsequent sequencing. χ² test was performed to analyze the relationship of APC polymorphisms or CRC occurrence with clinical features. COX regression was used to find out risk factors for CRC. Hazard ratio (HR) and 95% confidence interval (CI) represented the risk of CRC.

RESULTS

Clinical information on sex, regular physical activity, smoking history, alcohol use and polyps types was recorded. Neither D1822V nor E1317Q polymorphism was associated with these factors. In following analysis, we found significant difference in the frequency of males between CRC and non-CRC patients (87.4% vs. 58.7%, P < 0.001). Distinct difference in the distribution of D1822V polymorphism was also observed between CRC and non-CRC patients (P = 0.001). In COX analysis, sex was identified as a risk factor for transition from polyps to CRC (HR = 2.442, 95%CI = 1.281-4.654). D1822V polymorphism tended to inhibit the transition process (HR = 0.286, 95%CI = 0.170-0.480). However, E1317Q seemed to have no significant effect on this process (HR = 1.042, 95%CI = 0.676-1.606).

CONCLUSION

In a word, APC D1822V polymorphism has strong effect on the transition from polyps to CRC.

Genetic alterations related to endoscopic treatment of colorectal tumors

Background and Aim

Genetic indicators of endoscopic resection for colorectal carcinoma remain inconclusive. This study analyzed genetic changes in early colorectal tumors that could inform decisions for endoscopic procedures.

Methods

A total of 83 colorectal tumors from 81 patients, including adenoma (n = 7), Tis–T1a (n = 22), T1b (n = 14), and advanced carcinoma (n = 40), were analyzed. Tis tumors (n = 16) and some T1 carcinomas (n = 11) were analyzed as mixed adenomas and carcinomas. Lesions were laser‐capture microdissected for DNA extraction, and targeted sequencing of 50 cancer‐related genes was performed. Genetic data were then correlated with clinical records, including magnifying endoscopic findings.

Results

Numbers of gene alteration rates in TP53 and SMAD4 increased with tumor progression from adenoma to carcinoma. Frequencies of mutant variants in TP53 (P = 0.004) and rates of copy number loss in SMAD4 (P = 0.006) increased in carcinoma components of mixed tumors compared to adenoma components. Moreover, adenoma components of T1b carcinomas had higher TP53 mutation rates than Tis or T1a carcinomas (P = 0.011) and pure adenomas (P = 0.026). Gene alterations in TP53 (P = 0.0055) and SMAD4 (P = 0.0055) increased in cases with irregular surface patterns of magnifying endoscopic findings.

Conclusions

Numbers of copy number variations and TP53 and SMAD4 alterations were related to colorectal tumor progression. TP53 alteration rates in adenoma components were high in T1b carcinomas, warranting complete treatment with en bloc resection. Magnifying endoscopic findings might reflect the genetic status of colorectal tumors.

Analysis of molecular alterations in laterally spreading tumors of the colorectum

BACKGROUND

Colorectal laterally spreading tumors (LSTs) are classified into LST-Gs and LST-NGs, according to macroscopic findings. In the present study, we determined the genetic and epigenetic alterations within colorectal LSTs and protruding adenomas.

METHODS

A crypt isolation method was used to isolate DNA from tumors and normal glands of 73 macroscopically verified colorectal LSTs (histologically defined adenomas; 38 LST-Gs and 35 LST-NGs) and 36 protruding adenomas. The DNA was processed using polymerase chain reaction (PCR) microsatellite assays, single-strand conformation polymorphism (SSCP) assays, and pyrosequencing to detect chromosomal allelic imbalance (AI), mutations in APC, KRAS, and TP53, and the methylation of MLH1, MGMT, CDKN2A, HPP1, RASSF2A, SFRP1, DKK1, ZFP64, and SALL4 genes. In addition, methylation status was examined using the following set of markers: MIN1, MINT2, MINT31, MLH1, and CDKN2A (with classification of negative/low and high). Microsatellite instability (MSI) was also examined.

RESULTS

5q AI and methylation of the SFRP1 and SALL4 genes were common molecular events in both LST-Gs and LST-NGs. Neither MSI nor mutations in BRAF ware observed in the LSTs. TP53 mutations were rarely found in LSTs. The frequencies of KRAS and APC mutations and the methylation levels of ZFP64, RASSF2A, and HPP1 genes were significantly higher in LST-Gs than in LST-NGs. Protruding adenomas showed alterations common to LST-Gs. Negative/low methylation status was common among the three types of tumors.

CONCLUSION

Combined genetic and epigenetic data suggested that the molecular mechanisms of tumorigenesis were different between LST-Gs and LST-NGs.

Methyl jasmonate down-regulates survivin expression and sensitizes colon carcinoma cells towards TRAIL-induced cytotoxicity

BACKGROUND AND PURPOSE

Methyl jasmonate (MJ) is a plant stress hormone with selective cytotoxic anti-cancer activities. The TNF-related apoptosis-inducing ligand (TRAIL) death pathway is an attractive target for cancer therapy. Although TRAIL receptors are specifically expressed in primary cancer cells and cancer cell lines, many types of cancer cells remain resistant to TRAIL-induced cytotoxicity. Here we have assessed a possible synergy between MJ and TRAIL cytotoxicity in colorectal cancer (CRC) cell lines.

EXPERIMENTAL APPROACH

CRC cell lines were pre-incubated with sub-cytotoxic concentrations of MJ followed by TRAIL administration. Cell death was determined by XTT assay and microscopy. Cytochrome c release, caspase cleavage, TRAIL-associated factors, X-linked inhibitor of apoptosis (XIAP) and survivin protein levels were detected by immunoblotting. Survivin transcription was examined by RT-PCR.

KEY RESULTS

Pre-treatment with MJ resulted in increased TRAIL-induced apoptotic cell death, increased cytochrome c release and caspase cleavage. TNFRSF10A, TNFRSF10B, TNFRSF10D, Fas-associated death domain and cellular FLICE-like inhibitory protein remained unchanged during MJ-induced TRAIL sensitization, whereas MJ induced a significant decrease in survivin protein levels. Overexpression of survivin prevented MJ-induced TRAIL cytotoxicity, implying a role for survivin in MJ-induced TRAIL sensitization. MJ decreased survivin mRNA indicating that MJ may affect survivin transcription. In a β-catenin/transcription factor (TCF)-dependent luciferase activity assay, MJ decreased TCF-dependent transcriptional activity.

CONCLUSION AND IMPLICATIONS

MJ, at sub-cytotoxic levels, sensitized CRC cells to TRAIL-induced apoptosis. Thus, combinations of MJ and TRAIL, both selective anti-cancer agents, have potential as novel treatments for CRC.

Establishment and characterization of a new cell line derived from human colorectal laterally spreading tumor

AIM: To study the molecular mechanism of laterally spreading tumor (LST), a cell line [Laterally Spreading Tumor-Rectum 1 (LST-R1)] was derived and the characteristics of this cell line were investigated.

METHODS: A new cell line (LST-R1) originated from laterally spreading tumor was established. Properties of the cell line were characterized using scanning and transmission electron microscopy, immunohistochemistry method, cytogenetic analysis and nude mice xenograft experiments. In vitro invasion assay, cDNA microarray and Western blotting were used to compare the difference between the LST-R1 and other colorectal cancer cell lines derived from prudent colon cancer.

RESULTS: Our study demonstrated that both epithelial special antigen (ESA) and cytokeratin-20 (CK20) were expressed in LST-R1. The cells presented microvilli and tight junction with large nuclei. The karyotypic analysis showed hyperdiploid features with structural chromosome aberrations. The in vivo tumorigenicity was also demonstrated in nude mice xenograft experiments. The invasion assay suggested this cell line has a higher invasive ability. cDNA microarray and Western blotting show the loss of the expression of E-cadherin in LST-R1 cells.

CONCLUSION: We established and characterized a colorectal cancer cell line, LST-R1 and LST-R1 has an obvious malignant tendency, which maybe partially attributed to the changes of the expression of some adhesion molecules, such as E-cadherin. It is also a versatile tool for exploring the original and progressive mechanisms of laterally spreading tumor and the early colon cancer genesis.

Shifting from clinical to biologic indicators of prognosis after resection of hepatic colorectal metastases

Following resection of hepatic colorectal metastases, there are few criteria for predicting which patients have more aggressive disease and are, therefore, more likely to experience recurrence and reduced survival. Traditionally, primary tumor stage, preoperative carcinoembryonic antigen level, time from primary tumor treatment to diagnosis of hepatic metastases (disease-free interval), hepatic tumor size, number of hepatic metastases, and presence of extrahepatic disease have been reported to be predictors of survival after resection. However, the data regarding the prognostic importance of these clinicopathologic factors are inconsistent and conflicting. Therefore, conventional clinicopathologic factors may be inadequate for the purposes of prognostication. More recently, there has been increased interest in identifying biologic indicators that may help better define patients at risk for recurrence after hepatic resection for colorectal metastases. Recent studies have shown that proliferation markers such as p53 expression, tritiated thymidine uptake, thymidylate synthase, Ki-67, and human telomerase reverse transcriptase may be better predictors of outcome after resection of hepatic colorectal metastases. Moreover, tumor response to preoperative chemotherapy may also prove to be a useful predictor of outcome following liver resection for colorectal metastases.

Unventilated indoor coal-fired stoves in Guizhou province, China: cellular and genetic damage in villagers exposed to arsenic in food and air

BACKGROUND

Inorganic arsenic (iAs) is a well-known human carcinogen recognized by the World Health Organization and the International Agency for Research on Cancer. Currently, most iAs studies in populations are concerned with drinking water and occupational arsenicosis. In Guizhou province, arsenicosis caused by the burning of coal in unventilated indoor stoves is an unusual type of exposure. Because the poisoning mechanism involved in arsenicosis is as yet unknown and no effective therapy exists, progress has been slow on the prevention and therapy of arsenicosis.

OBJECTIVES

We examined the relationship between arsenic (As) exposure from the burning of coal in unventilated indoor stoves and genetic damage in humans, using cellular and molecular indices. We selected villagers from Jiaole township, Guizhou province, China, who had been exposed to milligram levels of As daily via food and air contaminated by the burning of As-containing coal in unventilated indoor stoves.

RESULTS

The As-exposed subjects from Jiaole were divided into four groups according to skin lesion symptoms: nonpatients, mild, intermediate, and severe arsenicosis. Another 53 villagers from a town 12 km from Jiaole were recruited as the external control group. In the four groups of exposed subjects, As concentrations in urine and hair were 76-145 microg/L and 5.4-7.9 microg/g, respectively. These values were higher than those in the external control group, which had As concentrations of 46 microg/L for urine and 1.6 microg/g for hair. We measured sister chromatid exchange and chromosomal aberrations to determine human chromosome damage, and for DNA damage, we measured DNA single-strand breaks and DNA-protein cross-links. All measurements were higher in the four exposed groups compared with the external control group. DNA repair was impaired by As exposure, as indicated by the mRNA of O-6-methylguanine-DNA methyltransferase (MGMT), X-ray repair complementing defective repair in Chinese hamster cells 1 (XRCC1), and, to a lesser extent, by the mismatch repair gene hMSH2 mRNA. The expression of mutant-type p53 increased with aggravation of arsenicosis symptoms, whereas the expression of p16-INK4(p16) decreased. p53 mutated at a frequency of 30-17% in the carcinoma (n = 10) and precarcinoma (n = 12) groups. No mutation was found in p16, although deletion was evident. Deletion rates were 8.7% (n = 23) and 38.9% (n = 18) in noncarcinoma and carcinoma groups, respectively.

CONCLUSIONS

The results showed that long-term As exposure may be associated with damage of chromosomes and DNA, gene mutations, gene deletions, and alterations of DNA synthesis and repair ability.

Clinicopathologic and immunohistochemical study of small apparently "de novo" colorectal adenocarcinomas

Rarely, adenocarcinomas of the colorectum develop as small (< or =1.0 cm) rapidly invasive tumors without an obvious adenomatous or "in situ" component. These tumors have been termed "de novo" carcinomas. Although it is believed by some that these tumors are more aggressive than conventional large adenocarcinomas with an identifiable in situ component, little is known about the biologic characteristics and natural history of these lesions. The aim of this study was to evaluate and compare the pathologic features, biologic characteristics, and natural history of small apparently de novo invasive colorectal adenocarcinomas with conventional large (>1.0 cm) carcinomas. Routinely processed specimens from 20 patients (M/F ratio: 13/7; mean age: 65 y) with small apparently de novo invasive colorectal adenocarcinomas (all < or =1.0 cm in size) were evaluated for a variety of clinical and pathologic features. In addition, immunostains for p53, beta-catenin, DPC4, hMLH1, hMSH2, and MGMT were evaluated in all cases. The findings in this group of cases were compared with those from 20 control patients (M/F ratio: 8/12; mean age: 60 y) with stage-matched conventional "large" colorectal adenocarcinomas (all >1.0 cm in size). Patients were followed for a mean of 52.6 and 60.6 months, respectively, for the 2 groups. Small apparently de novo invasive adenocarcinomas were present in the left colon, transverse colon, and right colon in 85%, 10%, and 5% of cases, respectively. Their mean size was 7 mm (range: 3 to 10 mm). All cases were stage T1 and the majority were moderately differentiated (75%). Only 1 (5%) patient had lymph node metastases. Two (10%) cases were mucinous and only 1 (5%) showed prominent tumor infiltrating lymphocytes. Upon complete sectioning of the tissue blocks of tumor, residual foci of adenomatous epithelium were present in 16/20 (80%) cases, of which 75% contained foci of high-grade dysplasia. P53 and nuclear beta-catenin staining was present in 70% and 85% of cases, respectively, but only 5 cases (25%) showed loss of DPC4. Loss of MGMT expression was seen in 5 cases (25%), loss of hMSH2 in only 1 case (5%), and none showed loss of hMLH1. Only 2 patients (10%) developed visceral metastases upon follow-up. Control patients had similar demographic features, clinical outcome, anatomic distribution of tumors, degree of differentiation, and prevalence of positivity for the immunostains noted above, to the study cases. In our patient population, true small de novo colorectal adenocarcinomas, tumors that lack an identifiable adenomatous component, are exceedingly rare, because complete tissue sectioning reveals residual adenomatous tissue in the majority of cases. The biologic characteristics and natural history of small carcinomas with a minimal dysplastic component, and those with no identifiable adenomatous component, are similar to conventional large (>1 cm) adenocarcinomas, and, thus, they should probably be treated similarly.

Associations of Ki-ras proto-oncogene mutation and p53 gene overexpression in sporadic colorectal adenomas with demographic and clinicopathologic characteristics

In colorectal tumorigenesis, Ki-ras proto-oncogene mutation often occurs early in the adenoma-adenocarcinoma sequence, whereas mutation of the p53 gene is associated with late progression to carcinoma. We evaluated the relationship of demographic and clinicopathologic characteristics to Ki-ras mutation and p53 gene product overexpression in 1,093 baseline sporadic colorectal adenomas from 926 individuals enrolled in a phase III recurrence prevention trial. Ki-ras mutation was found in 14.7% of individuals and p53 overexpression was found in 7.0% of those tested. Multivariate analysis found older age, rectal location, and villous histology to be independently associated with Ki-ras mutation. Individuals with an advanced adenoma (>or=1 cm or high-grade dysplasia or villous histology) had a 4-fold higher likelihood of Ki-ras mutation [odds ratios (OR), 3.96; 95% confidence intervals (CI), 2.54-6.18]. Ki-ras mutations in codon 12 and of the G-to-A transition type were more frequent in older individuals, whereas G-to-T transversion was more frequent in rectal adenomas than in the colon. Multivariate analysis showed that previous history of a polyp (P = 0.03) was inversely associated with p53 overexpression. Large adenoma size (>or=1 cm), high-grade dysplasia, and villous histology were independently associated with p53 overexpression, with the strongest association for advanced adenomas (OR, 7.20; 95% CI, 3.01-17.22). Individuals with a Ki-ras mutated adenoma were more likely to overexpress p53 (OR, 2.46; 95% CI, 1.36-4.46), and 94.8% of adenomas with both alterations were classified as advanced (P <or= 0.0001). Our large cross-sectional study supports the role of both Ki-ras and p53 in the progression of adenomas and shows that their molecular pathogenesis differs by anatomic location, age, and mucosal predisposition as evidenced by previous history of a polyp.

Interaction between morphology and angiogenesis in human early colorectal cancers

Morphologically, early colorectal cancers are divided into two types: polypoid cancers and non-polypoid cancers. They vary in growth pattern, progression, and genetic alteration. Angiogenesis between polypoid and non-polypoid cancers may also be different. Therefore, the present study aims to evaluate angiogenesis in the early stages of colorectal malignancy, with particular attention to the morphological differences. The serial slides of all materials (48 polypoid cancers, 10 non-polypoid cancers, 20 adenomas and 10 normal tissues) were immunohistochemically stained for three endothelial cell markers (CD31, von Willebrand factor and CD105), counted for the number of microvessels in the same hot spots, and the angiogenic status was estimated. Polypoid cancers had higher microvessel counts and were more predominantly supplied by activated (CD105-positive, newly forming) microvessels than non-polypoid cancers. The present study indicated the possibility that the difference in growth pattern might be explained by the difference in angiogenesis between polypoid and non-polypoid cancers.

Molecular validation of the modified Vienna classification of colorectal tumors

Although the Vienna classification has been introduced to resolve discrepancies in histological diagnoses of colorectal tumors between Western and Japanese pathologists, practical applications of this classification scheme have been problematic because invasion of the lamina propria of tumor cells is often difficult to recognize. Therefore, the following refinements of the classification criteria are needed: category 3, low-grade adenoma/dysplasia; category 4, intramucosal borderline neoplasia; 4-a, high-grade adenoma/dysplasia; 4-b, well-differentiated adenocarcinoma; category 5, definite carcinoma; 5-a, intramucosal moderately-differentiated adenocarcinoma; and 5-b, submucosal carcinoma. We attempted to test whether molecular genetic alterations are related to the modified classification scheme and whether they may help to further categorize the various intramucosal neoplasia grades of colorectal tumors. Two-hundred-thirty-two colorectal tumors were examined using flow cytometric analysis of DNA content, polymerase chain reaction microsatellite assays, and single-strand conformational polymorphism assays to detect abnormalities of DNA content, chromosomal allelic loss, and Ki-ras and p53 gene mutations. Microsatellite instability (MSI) was also examined. Frequencies of genetic alterations and DNA aneuploid states increased with an increase in the grade assigned according to the modified Vienna classification. MSI was a rare event in colorectal adenomas and their frequency of MSI did not correlate with tumor grade. The combined genetic and DNA ploidy data support the conclusion that analysis of genetic alterations and DNA aneuploid states may help in appropriate categorization of colorectal tumors according to the modified Vienna scheme. In addition, MSI-positive tumors may represent a specific subtype of colorectal adenomas.

Mutagen sensitivity and p53 expression in colorectal cancer in China

OBJECTIVE

This study was designed to investigate DNA damage and/or repair capability, non-random chromatid breakage, and p53 expression in patients with colorectal cancer.

METHODS

The bleomycin sensitivity assay was used in a case-control study to compare the DNA damage repair system between colorectal cancer patients and controls. G-banding was used to search for non-random chromatid breaks. Immunocytochemistry was used to investigate p53 expression in tumour tissues and adjacent normal tissues.

RESULTS

It was found that cases typically had a higher number of chromosome breaks than controls (0.84 v 0.69 breaks/cell, p<0.01). After correction by sex and age, the difference was still significant (F=4.38, p<0.05). The correlation coefficient between mutagen sensitivity and age was 0.31(p<0.05) in controls and 0.18 (p>0.05) in cases. The ratio of odds ratios among bleomycin resistant, sensitive, and hypersensitive classes was 1:2.31:3.85. Overexpression of p53 was detected in 25 of 47 tumour tissues independent of tumour stage. Cases who had a family history of cancer were susceptible to the p53 aberration (p<0.05). Chromosomes 1p, 5q, and 14q were susceptible to breakage in patients with colorectal cancer.

CONCLUSION

Patients with colorectal cancer show increased bleomycin induced chromatid breaks and may have minor DNA repair deficiencies. p53 aberration is an early event in the development of colorectal cancer, but no definite correlation is found between p53 overexpression and mutagen sensitivity.

p53 protein accumulation and p53 gene mutation in colorectal cancer

Comparison of immunohistochemical methods for detection of protein p53 accumulation and molecular techniques for analysis p53 gene mutation in colorectal cancer is presented. Thirty eight patients were included: all underwent surgery without preoperative treatment. Sex of patients, tumor localisation, macro and microscopic type of cancer and staging according to Astler-Coller and Jass classifications were evaluated. Protein p53 accumulation was detected by the streptavidin-biotin method using DO-7 (Dako) antibody. The number of cells stained were classified semiquanititatively according to a scoring system: (-)no positive cells, (+) : 10-30% positive cells, (++) : 40-70% positive cells, (+++) : >70% positive cells. For all cancer samples, exons 5 to 9 of p53 gene were amplified from isolated genomic DNA. PCR products were subjected to single standed conformational polymorphism analysis. All product were also directly sequenced on ABI PRISM 377 apparatus using fluorescent dideoxyterminators chemistry. The protein p53 accumulation was detected in 53% (20/38), whereas p53 gene mutation was seen in 55% (21/38). Among them, 15 patients (39%) with overexpression showed mutation in exon 5-8 gene p53. Discrepancies between results were noted in 29%. In conclusion, the necessity of both methods immunohistochemical and molecular is indicated for the objective evaluation of functional and structural status of p53 gene and protein.

Glut1 expression in T1 and T2 stage colorectal carcinomas: its relationship to clinicopathological features

Glucose uptake is mediated by glucose transporter (Glut) proteins, which exhibit altered expression in a variety of malignant neoplasms. Glut1 expression is thought to be a potential marker for malignant transformation. The aim of the present study was to investigate the expression of Glut1 protein in colorectal adenomas, T1 and T2 stage carcinomas. Immunohistochemical detection of Glut1 protein was examined in 141 formalin-fixed and paraffin-embedded colorectal tumour specimens (57 adenomas, 84 carcinomas). The degree of Glut1 immunostaining of a specimen was graded according to the proportion of Glut1-positive cells in it; absent (positive cells are 0%), weakly positive (less than 10%), moderately positive (10-50%), and strongly positive (more than 50%). Glut1 expression was present in 18% of the adenomas with low-grade dysplasia, and in 63% of the adenomas with high-grade dysplasia. The positivity in such lesions was usually weak, but was moderate in 8% of the adenomas with high grade dysplasia. For the carcinomas, there were significant correlations between Glut1-positivity and depth of invasion (T1 45% versus T2 74%, P<0.01), histological differentiation (well 49% versus moderately to poorly 74%, P< 0.05) and morphological type (polypoid 42% versus depressed 73%, P< 0.05), if the cut-off value was set at 10% of cells. In conclusion, we clarified the relationship between Glut1 expression and clinicopathological features in T1 and T2 stage colorectal carcinomas, and our results suggested a high malignant potential of the depressed-type carcinoma.

Expression of brain-type glycogen phosphorylase is a potentially novel early biomarker in the carcinogenesis of human colorectal carcinomas

OBJECTIVE

Our previous studies have demonstrated the significant role of brain-type glycogen phosphorylase (BGP) in the carcinogenesis of gastric carcinoma. The aims of the present study were to investigate the expression of BGP in colorectal carcinoma as well as the timing of this expression in the adenoma-carcinoma sequence (ACS), in comparison with the overexpression of p53 protein. We also sought to identify this marker in the particular colorectal mucosa bearing de novo carcinoma.

METHODS

The expression of BGP and p53 protein in colorectal carcinoma using affinity purified specific anti-human BGP antibody (Ab) and anti-p53 Ab was studied using 96 resected specimens. Further investigation to examine the timing of BGP expression in comparison with p53 overexpression was carried out using 13, 18, eight, and 16 specimens of adenoma with mild, moderate, and severe dysplasia, and carcinoma in adenoma, respectively. The BGP immunohistochemistry in whole resected human colorectal mucosa (two with carcinoma and one with ulcer) was carried out using specific anti-BGP and anti-p53 Ab.

RESULTS

The BGP visualized by immunohistochemistry was commonly present in colorectal carcinoma (83.3%). The expression of this molecule during ACS showed excellent correlation with the increased dysplasia and was found before p53 overexpression, whereas no BGP expression was seen in the normal human large intestine remote from the cancer foci. Positive staining in overtly normal-looking colonic mucosa was observed mainly around carcinomas without any adenoma component.

CONCLUSIONS

The present study is the first to localize the BGP molecule in colorectal carcinoma, adenoma, and normal mucosa. It is suggested that BGP is a novel biomarker for carcinogenesis in both the pathways of ACS and the de novo colorectal carcinoma.

Frequent allelic imbalance on chromosome 18q21 in early superficial colorectal cancers

Genetic alterations in early superficial colorectal cancers have rarely been reported. In the present study, we searched for alterations in the APC and p53 genes in 27 superficial (20 depressed and 7 elevated) and 21 protruding colorectal cancers with submucosal invasion by means of PCR-single strand conformation polymorphism. Allelic imbalance (AI) on five loci, i.e., 1p34-36, 8p21-22, 14q32, 18q21 and 22q12-13, was also analyzed. Since a high incidence of 18q21 AI was detected in the superficial depressed cases, we further screened for alterations in Smad2, Smad4 and DCC. APC alterations were observed in three superficial depressed, one superficial elevated, and 11 protruding colorectal cancers, indicating that the frequency of APC alterations in superficial depressed cases was significantly lower than that in the protruding ones. There was no significant association between p53 alterations and macroscopic types. AI on 18q21 (13/20, 65%) was much higher than those on the other four loci in the superficial depressed cases. Moreover, the frequency of 18q21 AI in the superficial depressed cases was significantly higher than that in the protruding ones. Smad4 alterations were only detected in 1 of the 13 superficial depressed and 3 of the 17 protruding cases, while Smad2 and DCC alterations were not detected in any case examined. These data suggest that the carcinogenetic pathways of protruding and superficial depressed colorectal cancers are different, and that alterations of tumor suppressor gene(s) located on 18q21 other than Smad2, Smad4 and DCC might be associated with most superficial depressed colorectal cancers.

Analysis of the p53/BAX pathway in colorectal cancer: low BAX is a negative prognostic factor in patients with resected liver metastases

PURPOSE

To determine the prognostic value of the central downstream apoptosis effector BAX in relation to its upstream regulator p53 in R0-resected hepatic metastases of colorectal cancer.

PATIENTS AND METHODS

Retrospective analysis of 41 patients who underwent potentially curative resection of liver metastases from colarectal cancer was performed. Tumor DNA was screened for p53 mutations by single-stranded conformational polymorphism polymerase chain reaction and for BAX frameshift mutations by fragment length analysis. Protein expression of BAX, p21, and p53 was investigated by immunohistochemistry.

RESULTS

Overall median survival was 40.2 months. Tumors with BAX frameshift mutations were considered microsatellite mutator phenotype-positive and were excluded from further prognostic analyses. Patients with high BAX protein expression had a median survival of 53.6 months compared with 35.4 months for patients with low BAX expression (P < .05). The negative prognostic value of low BAX expression was more evident in those patients with wild-type p53 (median survival, 54.0 v 23.3 months for BAX-negative tumors; P < .01). Low BAX expression was an independent negative prognostic marker in multivariate regression analysis for all patients independent of the p53 status (relative risk, 3.03, P = .03), especially for p53 wild-type tumors (relative risk, 8.21; P = .0095).

CONCLUSION

We conclude that low BAX expression is an independent negative prognostic marker in patients with hepatic metastases of colorectal cancer. The best survival was seen in patients with an intact p53-to-BAX pathway; ie, wild-type p53- and BAX-positive tumors. Thus, analysis of apoptosis signaling pathways (here, p53 in concert with its downstream death effector, BAX) might yield more prognostic power in future studies as compared with analysis of single genes such as p53 alone.

Loss of heterozygosity and microsatellite instability in de novo versus ex-adenoma carcinomas of the colorectum

Small adenocarcinomas of the colorectum showing no evidence of origin from an adenoma have been called de novo carcinomas, a name that implies an origin via a different molecular genetic mechanism than the usual colorectal carcinoma which develops from an adenoma. Using microsatellite analysis, 35 early (pT1) de novo and 36 pT1 ex-adenoma carcinomas were compared using 8 microsatellite loci at 6 different chromosomal loci (1p, 2p, 8p, 5q, 17p, and 18q) known or hypothesized to be important for colorectal carcinogenesis. The rate of loss of heterozygosity (LOH) at the 17p locus (near the p53 gene) was significantly higher in the de novo than in the ex-adenoma group (73 vs. 37%, P = 0.004). The rates of LOH at the other loci (including the APC and DCC genes) and the rate of MSI were not significantly different in the two groups. These results indicate that de novo carcinomas of the colorectum develop via a similar carcinogenetic pathway as conventional ex-adenoma carcinomas; however, their higher rate of LOH at 17p is evidence for a biologically more advanced lesion with more frequent p53 mutations, consistent with clinicopathological data indicating that de novo carcinomas are more aggressive than ex-adenoma carcinomas.

Loss of heterozygosity at the TP53 gene: independent occurrence from genetic instability events in node-negative breast cancer

TP53 abnormalities have been reported as an early event in the process of cellular transformation of human breast cancers, and involved in mammary-tumor evolution, from in situ to invasive disease. In this study, node-negative (N-) tumors were examined for TP53 allelic loss in relation to different genetic instability events, including allelic loss at chromosome 17p13.3 and c-H-ras-1 loci, as well as alteration of the c-myc and c-erbB-2/neu oncogenes. TP53 allelic loss was analyzed to determine whether such an abnormality was the more important, among other genetic events, in the N- tumors, whether it appeared independently of these genetic events, and whether accumulation of genetic events arises in this group of breast tumors. Clinicopathological parameters were also examined. Loss of heterozygosity (LOH) at the TP53 gene appears the most frequent alteration detected (26% vs. 13%, 8%, 9% and 3% for LOH at D17S30 and c-H-ras-1 loci, and amplification of c-myc and c-erbB-2/neu respectively). There was no association between LOH at the TP53 locus and other genetic events. Among clinicopathological parameters, significant associations were observed only with estrogen-receptor-negative tumors (p = 0.05). Our results demonstrate that LOH at TP53 arises more frequently in the N- breast cancer, thus supporting earlier findings suggesting that TP53 abnormality has a role early in the pathogenesis of breast lesions. Moreover, the data indicate that accumulation of many genetic events occurs at a low level in N- breast tumors, and that TP53 abnormality occurs independently of these genetic events.

TP53 mutations in stage I gallbladder carcinoma with special attention to growth patterns

32 stage I cases of gallbladder carcinoma (GC) were examined to evaluate TP53 mutations with special attention to growth patterns. Their growth patterns were classified into two types: polypoid (P-type) and flat (F-type). 16 cases of GC were classified as P-type and 16 as F-type. p53 immunohistochemistry was performed using a mouse monoclonal anti-p53 antibody. Mutations in exons 5-8 were examined by polymerase chain reaction single strand conformation polymorphism (PCR-SSCP) and direct sequencing. The incidence of p53 immunoreactivity was greater in the cases of F-type (11/16, 69%) than those in P-type (14/16, 25%) (P < 0.05). PCR-SSCP or direct sequencing revealed that TP53 mutations were detected in all cases positive for p53 protein. These results suggest that TP53 mutations may contribute to the carcinogenesis of the F-type GC, and than this pathway in the F-type may differ from that in the P-type GC.

Comparison of p53 gene abnormalities in bilateral and unilateral breast cancer

BACKGROUND

The results of recent studies have suggested that p53 gene abnormalities are associated with carcinogenesis in several neoplasms. It is believed that bilateral breast carcinomas develop as a result of a different carcinogenetic mechanism and genetic environment from those of unilateral lesions.

METHODS

p53 Gene abnormalities in bilateral primary breast cancer were detected by polymerase chain reaction-single strand comformation polymorphism (PCR-SSCP) analysis. A total of 76 paraffin embedded tissue specimens from 38 patients with bilateral primary breast cancer were examined, and 62 patients with unilateral breast cancer were analyzed as control subjects. The bilateral tumors were defined as primary, based on clinical parameters and the presence of an intraductal component. There were 13 patients with synchronous bilateral breast cancer and 25 with metachronous bilateral breast cancer.

RESULTS

p53 Gene abnormalities were detected in 50% of the bilateral and 25.8% of the unilateral cases, and the difference was significant (P < 0.01, chi-square test). Abnormalities were detected in 56% of the metachronous cases, representing a much higher incidence than that of the unilateral cases (P < 0.001, chi-square test). The incidence of p53 gene abnormalities in the first and second tumors of the metachronous cases was 44% and 68%, respectively. The percentage of patients with a p53 gene abnormality and positive family history was higher for those with bilateral than with unilateral breast cancer (P < 0.01, chi-square test).

CONCLUSION

These findings indicate that the genetic changes and mechanism of carcinogenesis in bilateral and unilateral breast cancer are different.