Endosonographic evaluation of c-kit-positive gastrointestinal stromal tumor

BACKGROUND

Endosonographic features of c-kit-positive gastrointestinal stromal tumors (GISTs) were compared with those of leiomyomas and schwannomas.

METHODS

Twenty-four patients with gastric mesenchymal tumors who underwent endoscopic ultrasonography (EUS) and surgical treatment were enrolled. GISTs were defined as c-kit (CD117)-positive tumors, leiomyomas as desmin-positive and c-kit-negative tumors, and schwannomas as S-100-positive and c-kit-negative tumors. Invasion to adjacent organs or more than 20 mitotic counts per 50 high power fields indicated malignancy.

RESULTS

There were 19 GISTs, three leiomyomas, and two schwannomas. All five malignant tumors were GISTs. A marginal halo was found in 12 of 19 GISTs and in both of the schwannomas, but not in any of the three leiomyomas. The echogenicities of GISTs were low but higher than that of the normal proper muscle layer, whereas those of leiomyomas and schwannomas were usually low. Lobulation of the tumor surface was documented only in GISTs, particularly in malignant ones. The tumor doubling time of a malignant GIST was 9.3 months, and that of six benign GISTs was 18.7 months (range = 10.7-28.0 months).

CONCLUSION

Marginal halo and relatively higher echogenicity on EUS might suggest GIST. Marginal lobulation and a short doubling time may be signs of a malignant GIST.

Visualizing the gastric wall with a 30-MHz ultrasonic miniprobe: ex vivo imaging of normal gastric sites and sites of early gastric cancer

BACKGROUND

This study was performed to determine the echo layer structures of the normal gastric wall and early gastric cancer when visualized with a 30-MHz ultrasonic miniprobe.

METHODS

Twelve surgically resected gastric specimens were used for an ex vivo study. Eighteen normal sites and 12 early gastric cancer sites were scanned with an Olympus (XUM-S30-25R) probe with a frequency of 30-MHz. Endoscopic ultrasound images were compared with corresponding histopathologic sections stained with hematoxylin and eosin.

RESULTS

The normal mucosa was visualized as at least four alternating echo layers; the muscularis mucosa was delineated at all normal sites. Lymphoid aggregates within the mucosa could be seen. The submucosa was clearly visualized in most cases, but the muscularis propria and subserosa were seldom depicted due to attenuation of ultrasound waves. At the sites of gastric cancer, the layered architecture of the mucosa was disturbed by an irregular hypoechoic lesion. Minimal submucosal infiltration (400 and 750 micrometer) was clearly depicted in two cases, without ulceration at or around the tumor site. However, attenuation at the site of a deep ulcer scar prevented adequate visualization of the tumor extent in two other cases with ulceration.

CONCLUSION

A 30-MHz ultrasonic miniprobe may provide additional imaging information of the gastric wall and could play a role in the assessment of early cancer lesions.

Gene mutation as a target for early detection in cancer diagnosis

The increasing number of genetic aberrations implicated in the development of human cancer has prompted a search to detect them at the earliest possible stage of their formation. Of the many such genetic changes identified thus far, relatively few meet the standard for markers in early diagnosis and prognosis, namely that the genetic modifications occur during the early onset phase of cancer development. Parallel to the increasing number of such genes is the growing availability of technologies using more powerful and cost-efficient methods that enable mass screening for genetic alterations. The purpose of this review is to summarize the currently available genes that can serve as markers for early detection of cancers and methods that allow their detection.

Distinct pattern of p53 phosphorylation in human tumors

The protein product of the tumor suppressor gene p53 is phosphorylated on multiple residues by several protein kinases. Using a battery of 10 antibodies developed against different phosphorylated and acetylated residues of p53, we compared the pattern of p53 phosphorylation and acetylation in tumor-derived cell lines, tumor samples, and non-neoplastic cells. Irrespective of tumor types or the presence of p53 mutation, phosphorylation and acetylation of p53 was substantially higher in samples obtained from tumor tissues than those found in non-transformed samples. Among the 10 sites analysed, phosphorylation of residues 15, 81, 392, and acetylation were among the more frequent modifications. Analysis of two of the more abundant phosphorylation or acetylation sites on p53 is sufficient to detect 72% of tumor-derived p53 proteins. The distinct pattern of p53 phosphorylation and acetylation in human tumors may offer a new means to monitor the status and activity of p53 in the course of tumor development and progression.

Jun NH2-terminal kinase phosphorylation of p53 on Thr-81 is important for p53 stabilization and transcriptional activities in response to stress

The p53 tumor suppressor protein plays a key role in the regulation of stress-mediated growth arrest and apoptosis. Stress-induced phosphorylation of p53 tightly regulates its stability and transcriptional activities. Mass spectrometry analysis of p53 phosphorylated in 293T cells by active Jun NH2-terminal kinase (JNK) identified T81 as the JNK phosphorylation site. JNK phosphorylated p53 at T81 in response to DNA damage and stress-inducing agents, as determined by phospho-specific antibodies to T81. Unlike wild-type p53, in response to JNK stimuli p53 mutated on T81 (T81A) did not exhibit increased expression or concomitant activation of transcriptional activity, growth inhibition, and apoptosis. Forced expression of MKP5, a JNK phosphatase, in JNK kinase-expressing cells decreased T81 phosphorylation while reducing p53 transcriptional activity and p53-mediated apoptosis. Similarly transfection of antisense JNK 1 and -2 decreased T81 phosphorylation in response to UV irradiation. More than 180 human tumors have been reported to contain p53 with mutations within the region that encompasses T81 and the JNK binding site (amino acids 81 to 116). Our studies identify an additional mechanism for the regulation of p53 stability and functional activities in response to stress.

Altered expression of p53 and p27 proteins, alone or combined, as a predictor of metastatic potential in early invasive carcinoma of colon and rectum--a comparative clinicopathologic and molecular analysis

To place the choice of therapy (endoscopic resection or radical surgery) in early invasive carcinoma (EIC) of colon and rectum on a more rational basis, this study sought to identify molecular predictors of metastasis. Several morphologic risk factors (histologic type, degree of tumor invasion, lymphatic and venous invasion) and expression of p53 and p27 proteins in the primary tumor were compared in 80 patients with EIC, including 12 (15%) with metastasis or recurrence (or both). Of the factors enumerated, deeper invasion of the submucosal layer, lymphatic-venous invasion, p53 overexpression, and decreased expression of p27 were correlated significantly with metastasis. The results also indicated that altered expression of p53 or p27 is independently relevant to metastasis of EIC. Analysis of these markers, together with determination of the morphologic risk factors, could complement the identification of patients with metastasis on the basis of known morphologic risk factors. Because the molecular factors can be assessed more objectively than can the morphologic parameters, they may strengthen the ability to identify EIC that has undergone, or will undergo, metastasis.

Presacral ganglioneuroma arising in an elderly man with persistent constipation

Presacral ganglioneuroma in a 70-year-old man with persistent constipation and its features on computed tomography, magnetic resonance, and endoscopic ultrasonography are presented. Barium enema study and laparotomy showed that constipation was caused mainly by extrinsic compression from this tumor. Computed tomography, magnetic resonance, endoscopic ultrasonographic features such as well-defined solid tumor with a cystic component and punctate calcifications may facilitate early diagnosis of this rare tumor.

Altered expression of beta-catenin and c-erbB-2 in early gastric cancer

To investigate the possible relationship between altered expression (loss of membranous staining or nuclear accumulation) of beta-catenin and invasion/metastasis in early gastric cancer (EGC), beta-catenin was detected immunohistochemically in 116 cases of EGC, including 86 differentiated and 30 undifferentiated carcinomas. In parallel, immunohistochemical expression of c-erbB-2 was analyzed in all EGC cases. Regardless of histological type, altered expression of beta-catenin was found in 47% of mucosal carcinomas and 89% of carcinomas with submucosal invasion (p<0.001). Of particular interest is that beta-catenin alteration was found in almost all EGCs with lymph node metastasis, even though no significant statistical comparison could be made. These results suggest that molecular changes resulting in abnormal beta-catenin expression participate in the process of submucosal invasion and metastasis. While loss of expression was preferentially observed in undifferentiated EGCs, nuclear accumulation was found exclusively in 24% of differentiated EGCs. c-erbB-2 was overexpressed in only 16% of differentiated EGCs but there was no correlation between this overexpression and invasion or metastasis. However, it is intriguing that 12 out of 14 cases with c-erbB-2 overexpression also showed altered beta-catenin expression, suggesting that both molecules are involved in the development of a certain set of differentiated EGCs.

Quantitative enriched PCR (QEPCR), a highly sensitive method for detection of K-ras oncogene mutation

We have developed a rapid and highly sensitive method for the detection of mutant K-ras codon 12 allele in the presence of 10(5) copies of the wild-type alleles. This sensitivity is achieved by selective amplification of mutant K-ras sequences, using a two-stage procedure with modified primers. In the first stage, primers consist of K-ras sequences in the 3' portion and polyomavirus sequence (to minimize homology with human genome) on the 5' portion. The 3' portion also consists of mismatch sequence that generates an MvaI site in normal, but not mutant, K-ras codon 12 alleles. Thus, following the first round of 20 cycles, restriction enzyme cleavage is carried out to selectively digest normal K-ras codon 12 alleles. To enrich mutant alleles, a second amplification is performed using tail primers that recognize the polyoma, but not human sequences. This design ensures that in the second amplification only mutant alleles that were pre-amplified in the first round would serve as template for this reaction. Ethidium bromide-stained polyacrylamide gel electrophoresis (PAGE) of second-stage PCR product that has been digested with MvaI is used to monitor the presence of mutant alleles, detected at sensitivity of 1/10(5). This technique offers high sensitive detection of mutant K-ras alleles using a new concept of tail-primer design and is likely to assist in identifying patients at risk to develop pancreatic, colon, or lung cancer, which harbor high incidence of mutant ras alleles.

K-ras mutation: early detection in molecular diagnosis and risk assessment of colorectal, pancreas, and lung cancers--a review

Multiple genomic alterations are involved in the development of most human cancers. They include alterations in oncogenes, tumor suppressor genes, DNA mismatch repair and excision repair genes. Genetic testing for susceptibility has been a part of the management of patients with well-defined but uncommon hereditary cancers in which certain susceptible gene mutations are determined in the germ line. However, a molecular diagnostic approach to sporadic cancers, which comprise the vast majority of malignant tumors in human beings, is still under development. One of the best characterized tumor-related genes is K-ras, which somatically mutates in several types of sporadic human cancers. Since mutations of this gene occur exclusively in three hot spots (codons 12, 13 and 61), and are frequently detected and well characterized in colorectal, pancreas and lung cancers, molecular diagnosis and susceptibility (risk) assessment targeting K-ras mutations are being developed. For this purpose, sample collection methods that reflect the state of the entire affected organ are important. Clinical samples used for molecular diagnosis and risk assessment include stool and lavage fluid, pancreatic and duodenal juices, and sputum and lavage fluids for colorectal, pancreas and lung cancers, respectively. The reported incidence of K-ras mutations detected in these samples ranges from 7% to 80% for colorectal cancers, 25% to 87% for pancreatic cancers, and 25% to 48% for lung cancers. Incidence of mutations clearly depends on the sensitivity of the method for detecting the mutant K-ras allele, as well as the nature and the quality of the clinical samples. Various methods including plaque hybridization, dot blot hybridization, combined PCR and RFLP or SSCP, and sensitive PCR have been used, and they exhibited high specificity (75 to 100%) in detecting mutations. Molecular analysis is demonstrating promise in assessing susceptibility to, or risk of developing, sporadic cancers.

Wnt/beta-catenin signaling induces the expression and activity of betaTrCP ubiquitin ligase receptor

Beta-transducing repeat-containing protein (betaTrCP) targets the ubiquitination and subsequent degradation of both beta-catenin and IkappaB, thereby playing an important role in beta-catenin/Tcf and NF-kappaB-dependent signaling. Here evidence is presented that beta-catenin/Tcf signaling elevates the expression of betaTrCP mRNA and protein in a Tcf-dependent manner, which does not require betaTrCP transcription. Induction of betaTrCP expression by the beta-catenin/Tcf pathway results in an accelerated degradation of the wild-type beta-catenin, suggesting that the negative feedback loop regulation may control the beta-catenin/Tcf pathway. This signaling also upregulated NF-kappaB transactivation without affecting the activity of IkappaB kinase, thereby establishing that the maintenance of the betaTrCP level is important for coordination between beta-catenin/Tcf and NF-kappaB signaling.

Analysis of JNK, Mdm2 and p14(ARF) contribution to the regulation of mutant p53 stability

Identification of Mdm2 and JNK as proteins that target degradation of wt p53 prompted us to examine their effect on mutant p53, which exhibits a prolonged half-life. Of five mutant p53 forms studied for association with the targeting molecules, two no longer bound to Mdm2 and JNK. Three mutant forms, which exhibit high expression levels, showed lower affinity for association with Mdm2 and JNK in concordance with greater affinity to p14(ARF), which is among the stabilizing p53 molecules. Monitoring mutant p53 stability in vitro confirmed that, while certain forms of mutant p53 are no longer affected by either JNK or Mdm2, others are targeted for degradation by JNK/Mdm2, albeit at lower efficiency when compared with wt p53. Expression of wt p53 in tumor cells revealed a short half-life, suggesting that the targeting molecules are functional. Forced expression of mutant p53 in p53 null cells confirmed pattern of association with JNK/Mdm2 and prolonged half-life, as found in the tumor cells. Over-expression of Mdm2 in either tumor (which do express endogenous functional Mdm2) or in p53 null cells decreased the stability of mutant p53 suggesting that, despite its expression, Mdm2/JNK are insufficient (amount/affinity) for targeting mutant p53 degradation. Based on both in vitro and in vivo analyses, we conclude that the prolonged half-life of mutant p53 depends on the nature of the mutation, which either alters association with targeting molecules, ratio between p53 and targeting/stabilizing molecules or targeting efficiency.

Environmental factors as regulators and effectors of multistep carcinogenesis

This review highlights current knowledge of environmental factors in carcinogenesis and their cellular targets. The hypothesis that environmental factors influence carcinogenesis is widely supported by both epidemiological and experimental studies. The fact that only a small fraction of cancers can be attributed to germline mutations in cancer-related genes further buttresses the importance of environmental factors in carcinogenesis. Furthermore, penetrance of germline mutations may be modified by either environmental or other genetic factors. Examples of environmental factors that have been associated with increased cancer risk in the human population include chemical and physical mutagens (e.g. cigarette smoke, heterocyclic amines, asbestos and UV irradiation), infection by certain viral or bacterial pathogens, and dietary non-genotoxic constituents (e.g. macro- and micronutrients). Among molecular targets of environmental influences on carcinogenesis are somatic mutation (genetic change) and aberrant DNA methylation (epigenetic change) at the genomic level and post-translational modifications at the protein level. At both levels, changes elicited affect either the stability or the activity of key regulatory proteins, including oncoproteins and tumor suppressor proteins. Together, via multiple genetic and epigenetic lesions, environmental factors modulate important changes in the pathway of cellular carcinogenesis.

Collagen production by cultured human retinal pigment epithelial cells

We investigated extracellular matrix produced by human retinal pigment epithelial cells (RPE) in vitro using electron microscopy and enzyme linked immunosorbent assay (ELISA). The thickness of the matrix under the cell layer was about 30 microns after 360 days of culture. It consisted mainly of fibrous and granular components. Type IV and V collagen were detected but type I and III were not detected by ELISA. It appeared that RPE can secrete type IV and V collagen and form a thick membrane which may cause proliferative vitreoretinopathy (PVR) by contraction. Control of RPE proliferation and secretion of extracellular matrix is indispensable for prevention of PVR.

[Correlations between risk factors for metastasis in early tumors of the large intestine]

Intramucosal colorectal cancers (Tis) are treated by local excision. Controversies remain as to the management of patients with the submucosally invasive colorectal cancers (EIC). The decision for radical surgery or local excision depends on an estimate of the risk of metastases.

AIM

To estimate correlations between the risk factors for metastases in EIC and to evaluate the tests that identify the metastasising EICs. In the study, we investigated the relationships between selected prognostic factors (the gross appearance, depth of submucosal invasion, vessel invasion, grade, presence of adenoma component, and p53 overexpression) and the frequency of metastases in 64 EICs.

STATISTICAL ANALYSIS

Fisher's exact test and log-linear analysis. Tests' evaluation: sensitivity, specificity, predictive values. The metastases were detected in 11 tumours (17%). The metastases were found with the significantly (p < 0.05) higher frequency in moderately differentiated adenocarcinomas, in tumours with massive invasion, with vessel invasion, and with the p53 overexpression. The only interaction was between the grade and the depth of invasion. No other interaction between the risk factors was found with the multivariate analysis. The evaluation of the depth of invasion was characterised by the highest sensitivity in detecting metastases, and by the highest negative predictive value. The highest specificity and the positive predictive value were found for the evaluation of vessel invasion. The massive submucosal invasion, vessel invasion, moderately differentiated characteristics, and the p53 overexpression seem to be the independent risk factors for metastases in EIC. The evaluation of these factors should be helpful as prognostic tests and for the proper choice of the treatment modality for the patients with EIC.

Does p53 overexpression cause metastases in early invasive colorectal adenocarcinoma?

OBJECTIVE

To find out whether p53 overexpression correlates with metastatic potential and other adverse prognostic factors in early invasive colorectal carcinoma and whether measurement of the expression of p53 protein could be helpful in the choice of treatment (endoscopic/local or radical resection).

DESIGN

Retrospective study.

SETTING

University hospital, Japan.

SUBJECTS

Overexpression of p53 protein in the primary tumour was examined immunohistochemically in 50 patients with early invasive colorectal cancer.

MAIN OUTCOME MEASURES

Differences in p53 overexpression between subgroups.

RESULTS

Abnormal accumulation of nuclear p53 was detected in the primary tumour of 20 patients (40%) with early invasive colorectal cancer. We found p53-positive cells in 7 (78%) of 9 that had metastasised to regional lymph nodes or distant organs, or both, and in 13 (32%) of 41 that had not metastasised (p = 0.02). p53 Immunoreactivity was also present in 10 (71%) of 14 superficial (type II) lesions compared with 10 (28%) of 36 protruding (type I) ones (p = 0.009) and in 12 (57%) of 21 moderately differentiated adenocarcinomas compared with 8 (28%) of 29 well-differentiated adenocarcinomas (p = 0.045). There was no significant correlation between p53 overexpression and the depth of tumour invasion or angiolymphatic involvement. The p53-positive metastasising tumours had features that corresponded to those of early carcinoma arising de novo.

CONCLUSION

Our results seem to support the postulate that p53 overexpression in early invasive colorectal carcinomas is associated with an increase in their metastatic potential.

Combined analysis of microsatellite instability and K-ras mutation increases detection incidence of normal samples from colorectal cancer patients

Microsatellite instability (MI) and K-ras oncogene mutation have been widely used as biomarkers of genetic changes in colorectal cancer (CRC). Each of these biomarkers was independently found in normal-appearing colonic mucosa at stages preceding the development of CRC, albeit at a relatively low incidence. To assess the potential value of combined MI and K-ras mutation analysis in the detection of normal-appearing colonic mucosa samples taken from patients with CRC, we have chosen to analyze multiple (3-7) normal colonic mucosa samples and the respective colorectal tumor tissues from 20 patients with CRC. As a control, we have used 54 normal mucosa samples obtained from 9 autopsies of patients without CRC. In at least 1 of 5 loci analyzed, MI was found in 8 of 20 patients via analysis of multiple normal-appearing colonic mucosa samples from each patient. Combined analysis of MI and mutant ras alleles in normal-appearing colonic mucosa samples enabled the identification of 11 of 20 patients with CRC. None of the 54 normal colonic mucosa samples obtained from 9 patients without CRC were found to carry mutant ras or MI. The ability to detect 55% of patients with CRC via the analysis of normal mucosa samples provides an important advance in our approach toward early detection of individuals who may be at risk to develop this tumor type.

Conformation-dependent phosphorylation of p53

Phosphorylation of the p53 tumor suppressor protein is known to modulate its functions. Using bacterially produced glutathione S-transferase (GST)-p53 fusion protein and baculovirus-expressed histidine-tagged p53 ((His)p53), we have determined human p53 phosphorylation by purified forms of jun-N-kinase (JNK), protein kinase A (PKA), and beta subunit of casein kinase II (CKIIbeta) as well as by kinases present in whole cell extracts (WCEs). We demonstrate that PKA is potent p53 kinase, albeit, in a conformation- and concentration-dependent manner, as concluded by comparing full-length with truncated forms of p53. We further demonstrate JNK interaction with GST-p53 and the ability of JNK to phosphorylate truncated forms of GST-p53 or full-length (His)p53. Dependence of phosphorylation on conformation of p53 is further supported by the finding that the wild-type form of p53 (p53wt) undergoes better phosphorylation by CKIIbeta and by WCE kinases than mutant forms of p53 at amino acid 249 (p53(249)) or 273 (p53(273)). Moreover, shifting the kinase reaction's temperature from 37 degrees C to 18 degrees C reduces the phosphorylation of mutant p53 to a greater extent than of p53wt. Comparing truncated forms of p53 revealed that the ability of CKIIbeta, PKA, or WCE kinases to phosphorylate p53 requires amino acids 97-155 within the DNA-binding domain region. Among three 20-aa peptides spanning this region we have identified residues 97-117 that increase p53 phosphorylation by CKIIbeta while inhibiting p53 phosphorylation by PKA or WCE kinases. The importance of this region is further supported by computer modeling studies, which demonstrated that mutant p53(249) exhibits significant changes to the conformation of p53 within amino acids 97-117. In summary, phosphorylation-related analysis of different p53 forms in vitro indicates that conformation of p53 is a key determinant in its availability as a substrate for different kinases, as for the phosphorylation pattern generated by the same kinase.

Sclerosing pancreatitis showing rapidly progressive changes with recurrent mass formation

CONCLUSION

Sclerosing pancreatitis might develop repeatedly or might rapidly extend to the whole pancreas with recurrent mass formation.

BACKGROUND

Nothing is known concerning course or development of sclerosing pancreatitis.

METHODS

A 63-yr-old male was followed up for 2.5 yr.

RESULTS

The patient was admitted because of a tumor in the body and tail of the pancreas. Serum pancreatic enzymes were transiently elevated, but tumor markers were all negative. Imaging studies showed a tumor 7 cm in size. The main pancreatic duct was normal in the head and obstructed at the body on endoscopic retrograde pancreatography (ERCP). The K-ras oncogene mutation was positive in pure pancreatic juice. Distal pancreatectomy was performed because pancreatic cancer was highly suspected. Pathological findings showed that the tumor was a densely fibrotic mass without malignant cells. Inflammatory cell infiltration was observed in the stroma. One year later, another mass 3 cm in size was noted in the remnant pancreatic head. ERCP revealed diffuse irregular narrowing of the main pancreatic duct, its branches, and the common bile duct. Liver dysfunction improved and an elevation of serum pancreatic enzymes subsided without any specific treatment, and the mass diminished in size. The patterns of various imaging studies on the second tumor were the same as those of the previous resected mass. Corticosteroid was not administered.

Analysis of mutant K-ras in multiple sites of normal appearing mucosa of colorectal cancer patients

While 50% of colorectal tumors were found to harbor K-ms codon 12 mutation, only 18% of the respective patients contain this mutation in the normal appearing tissue when enriched PCR, a sensitive method that enables detection of one mutant allele in 10(4) normal alleles, is used. To determine whether the lower percentage could be attributed to the low incidence of this mutation or to the method of sampling, we have analyzed multiple normal appearing samples obtained from the same patient. Of 90 non-neoplastic mucosal samples collected from 20 patients with colorectal cancer, K-ras codon 12 mutation was identified in 6 samples taken from 5 patients. These results indicate that only one or two of the multiple samples contain mutant ras alleles. The presence of mutant ras alleles in the normal appearing tissues did not always correlate with that in the tumor site with respect to its presence and/or the type of base pair alterations, indicating independent or late events. While pointing to the importance of proper sampling method, the ability to detect ms mutation in normal mucosal tissues suggests it may serve as a useful biomarker of internal/external exposure which precede colorectal cancer development.

[Comparative study on biological difference between gastric cancer and colorectal cancer]

In this study, we investigated the clinico-pathologic characteristics of patients with adenocarcinoma of the stomach and those with colorectal carcinoma to compare early progression patterns of both tumors. Histologically, gastric and colorectal adenocarcinomas showed similar progression patterns, including the incidence of submucosal invasion, lymphatic infiltration and lymph node metastasis. One striking finding was in gross appearance in born tumors. In contrast to most gastric well differentiated adenocarcinoma (DTA), which showed superficial growth, colorectal DTAs mainly showed polypoid growth. However, the superficial-type colorectal DTAs invaded the submucosal layer more frequently than did polypoid DTAs and gastric DTAs. These findings indicate that superficial-type colorectal DTAs grow more rapidly and aggressively than do polypoid DTAs and gastric DTAs. In order to elucidate growth rates between gastric cancer and colorectal cancer with hepatic metastasis doubling time was measured by exponential growth of tumor marker (CEA or AFP). The doubling time of liver metastases calculated from tumor markers was 26.6 +/- 10.8 days for stomach cancer and 57.8 +/- 35.4 days for colorectal cancer; accordingly doubling time for gastric cancer was approximately half of that for colonic cancer. However, there were no other factors (age, sex, site, histologic type in stomach, tumor marker production, etc.) influencing doubling time.

Frequent and characteristic K-ras activation in aberrant crypt foci of colon. Is there preference among K-ras mutants for malignant progression?

BACKGROUND

To investigate very early lesion of colorectal cancer, K-ras activation and nuclear p53 accumulation were studied in aberrant crypt focus (ACF).

METHODS

ACF were microscopically identified in grossly normal mucosa of patients with colorectal cancer who underwent surgery. Each ACF was microdissected from the surgical specimen and divided into two pieces, one for histologic and immunohistochemical examinations and the other for K-ras activation. K-ras mutations in codons 12 and 13 were sequenced after being screened by polymerase chain reaction amplification followed by restriction fragment length polymorphism analysis. Intranuclear accumulation of p53 protein was immunostained with the avidin-biotin complex method.

RESULTS

ACF was predominantly distributed in the sigmoid colon and rectum, and its incidence was increased with age. Unexpectedly, ACF was very rare in colons of three patients with hereditary nonpolyposis colorectal carcinoma. K-ras mutations were detected in 58% (33 of 57) of ACF cases and in 44% (11 of 25) of adenocarcinoma cases. Although GTT mutation in codon 12 was predominantly observed in adenocarcinoma (10 of 11), GAT mutation (12 of 33) was as frequent as GTT mutation (11 of 33) in ACF together with mutation at codon 13 (7 of 33). No accumulation of p53 protein was found in any ACF.

CONCLUSION

ACF were not diagnosed as neoplasms histologically, but they were considered to be neoplastic lesions, and K-ras activation is one of the key events to form ACF. The G-T substitution in K-ras codon 12 may undergo malignant growth easily compared with G-A substitution in colorectal carcinogenesis.

Mutant K-ras in apparently normal mucosa of colorectal cancer patients. Its potential as a biomarker of colorectal tumorigenesis

BACKGROUND

The best way to reduce the incidence of colorectal cancer mortality would be to prevent this cancer. However, none of the biomarkers proposed can accurately identify persons at increased risk of colorectal cancer or those at low risk. As a possible genetic biomarker, K-ras mutations, which are frequently found in colorectal cancers, were analyzed in apparently normal colorectal mucosa.

METHODS

Nonneoplastic mucosa and tumor tissues were collected at surgery from 70 patients with colorectal cancer: one sample each from 50 patients (group A) and multiple samples from the other 20 patients (group B). Mutant K-ras codon 12 was analyzed by the enriched polymerase chain reaction (EPCR), by which one mutant can be detected among 10(3) to 10(4) normal alleles.

RESULTS

Only with the aid of EPCR was mutant K-ras detected in nonneoplastic mucosa of nine patients (18%) in Group A and five patients (25%) in Group B. This increased incidence could be attributed to the multiple tissue sampling. The presence of mutant K-ras in nonneoplastic mucosae was not consistently correlated with that in the tumors. These findings suggest that the mutant K-ras identified in nonneoplastic mucosa actually represents de novo mutations, which may be initiated by different etiologic factors and at different times.

CONCLUSION

Mutant K-ras detected in apparently normal mucosa should be a useful biomarker for identifying persons at higher risk of colorectal cancer. Our study also emphasizes the need for improving the method for sample collection to achieve true representation of the colorectal mucosa.

Frequent and characteristic K-ras activation and absence of p53 protein accumulation in aberrant crypt foci of the colon

BACKGROUND/AIMS

The relationship of aberrant crypt foci (ACF) to colorectal carcinogenesis is still controversial. Histological examination and analyses of K-ras mutations and p53 gene expression were performed to characterize ACF.

METHODS

ACF were identified microscopically in grossly normal colorectal mucosa. The ACF were separated into two pieces, one for histological and immunohistochemical examinations and the other for molecular analysis. K-ras mutations in codons 12 and 13 were analyzed by polymerase chain reaction amplification, followed by restriction fragment length polymorphism and sequencing analyses. Intranuclear p53 protein was immunostained by the avidin-biotin complex method.

RESULTS

Histologically, elongation and apical branching of the crypts in ACF were striking. K-ras mutations were detected in 58% of ACF (33 of 57; 46% [26 of 57] in codon 12, and 12% [7 of 57] in codon 13) and in 44% of adenocarcinomas (11 of 25; all in codon 12). In ACF, GAT mutations (12 of 26) were as frequent as GTT mutations (11 of 26) in codon 12, although GTT mutations in codon 12 were predominant in adenocarcinomas (10 of 11). No accumulation of p53 protein was detected in any ACF, although it was detected in 52% (13 of 25) of the colorectal carcinomas.

CONCLUSIONS

ACF do not seem histologically to be neoplasms, although genetically they are monoclonal lesions. K-ras mutation is critical in the formation of ACF, but p53 alteration could play a causal role in tumor progression.