Neoadjuvant chemoradiotherapy with or without panitumumab in patients with wild-type KRAS, locally advanced rectal cancer (LARC): a randomized, multicenter, phase II trial SAKK 41/07.

BACKGROUND: We conducted a randomized, phase II, multicenter study to evaluate the anti-epidermal growth factor receptor (EGFR) mAb panitumumab (P) in combination with chemoradiotherapy (CRT) with standard-dose capecitabine as neoadjuvant treatment for wild-type KRAS locally advanced rectal cancer (LARC). PATIENTS AND METHODS: Patients with wild-type KRAS, T3-4 and/or N+ LARC were randomly assigned to receive CRT with or without P (6 mg/kg). The primary end-point was pathological near-complete or complete tumor response (pNC/CR), defined as grade 3 (pNCR) or 4 (pCR) histological regression by Dworak classification (DC). RESULTS: Forty of 68 patients were randomly assigned to P + CRT and 28 to CRT. pNC/CR was achieved in 21 patients (53%) treated with P + CRT [95% confidence interval (CI) 36%-69%] versus 9 patients (32%) treated with CRT alone (95% CI: 16%-52%). pCR was achieved in 4 (10%) and 5 (18%) patients, and pNCR in 17 (43%) and 4 (14%) patients. In immunohistochemical analysis, most DC 3 cells were not apoptotic. The most common grade ≥3 toxic effects in the P + CRT/CRT arm were diarrhea (10%/6%) and anastomotic leakage (15%/4%). CONCLUSIONS: The addition of panitumumab to neoadjuvant CRT in patients with KRAS wild-type LARC resulted in a high pNC/CR rate, mostly grade 3 DC. The results of both treatment arms exceeded prespecified thresholds. The addition of panitumumab increased toxicity.

Dual role of DNA methylation inside and outside of CTCF-binding regions in the transcriptional regulation of the telomerase hTERT gene.

Expression of hTERT is the major limiting factor for telomerase activity. We previously showed that methylation of the hTERT promoter is necessary for its transcription and that CTCF can repress hTERT transcription by binding to the first exon. In this study, we used electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) to show that CTCF does not bind the methylated first exon of hTERT. Treatment of telomerase-positive cells with 5-azadC led to a strong demethylation of hTERT 5'-regulatory region, reactivation of CTCF binding and downregulation of hTERT. Although complete hTERT promoter methylation was associated with full transcriptional repression, detailed mapping showed that, in telomerase-positive cells, not all the CpG sites were methylated, especially in the promoter region. Using a methylation cassette assay, selective demethylation of 110 bp within the core promoter significantly increased hTERT transcriptional activity. This study underlines the dual role of DNA methylation in hTERT transcriptional regulation. In our model, hTERT methylation prevents binding of the CTCF repressor, but partial hypomethylation of the core promoter is necessary for hTERT expression.

Alterations of the Wnt signaling pathway during the neoplastic progression of Barrett's esophagus.

Aberrant activation of the Wnt signaling pathway has been reported during neoplastic progression in Barrett's esophagus (BE). However, mutations in APC and CTNNB1 genes were rarely observed. In this study, expression pattern of Wnt ligands, Frizzled receptors and APC, as well as the methylation status of the APC, SFRP1 and SFRP2 promoter genes were investigated in normal esophageal mucosa and in preneoplastic and neoplastic lesions of BE patients. Promoter methylation of APC was found in all BE samples and in 95% of esophageal adenocarcinomas (EAC). Full methylation of APC correlated with lack of expression. In EAC, nuclear translocation of beta-catenin was observed regardless of the expression of APC. WNT2 expression was higher in dysplasia and EAC than in BE, with 20/26 (77%) of the EAC showing high expression of WNT2. SFRP1 methylation occurred in all BE samples and in 96% of EAC, while SFRP2 was methylated in 73% of the normal squamous esophageal mucosa samples. In conclusion, (1) alterations of key regulators of the Wnt signaling are frequent in the pathogenesis of BE; (2) the APC and SFRP1 genes are inactivated by promoter methylation in BE; (3) the WNT2 gene is upregulated along the progression from low-grade dysplasia to EAC.

Telomerase activity and human telomerase reverse transcriptase mRNA expression in soft tissue tumors: correlation with grade, histology, and proliferative activity.

Telomerase activity (TA) is detected in most human cancers but, with few exceptions, not in normal somatic cells. Little is known about TA in soft tissue tumors. We have examined a series of benign and malignant soft tissue tumors for TA using the telomerase repeat amplification protocol assay. Analysis of the expression of the human telomerase reverse transcriptase was also carried out using RT-PCR. TA was undetectable in benign lesions (15 of 15) and low-grade sarcomas (6 of 6) and was detectable in 50% (19 of 38) of intermediate-/high-grade sarcomas. Although the presence of TA in soft tissue tumors is synonymous with malignancy, it is neither a reliable method in making the distinction between reactive/benign and malignant (especially low-grade) lesions nor a reliable marker of tumor aggressiveness. Leiomyosarcomas and storiform/pleomorphic malignant fibrous histiocytomas rarely showed TA, irrespective of their grade. A strong correlation between human telomerase reverse transcriptase mRNA expression and TA was observed, supporting the close relationship between both parameters. No significant relationship was observed between proliferative activity (as assessed by MIB-1 immunolabeling) and TA. We verified that the absence of telomerase expression was not due to the presence of telomerase inhibitors and therefore alternative mechanism(s) for cell immortalization, yet to be determined, seem to be involved in the development and/or maintenance of some soft tissue sarcomas.

A methylation sensitive dot blot assay (MS-DBA) for the quantitative analysis of DNA methylation in clinical samples.

BACKGROUND: There is increasing interest in DNA methylation and in its implication in transcriptional gene silencing, a phenomenon commonly seen in human cancer. AIMS: To develop a new method that would allow quantitative DNA methylation analysis in a large range of clinical samples, independently of the processing protocol. METHODS: A methylation sensitive dot blot assay (MS-DBA) was developed, which is quantitative and combines bisulfite modification, PCR amplification using primers without CpG sites, and dot blot analysis with two probes specific for methylated and unmethylated DNA. RESULTS: The established method was used to study methylation of the hTERT, APC, and p16 promoter regions in microdissected, formalin fixed and paraffin wax embedded tissues. CONCLUSIONS: MS-DBA is a sensitive, specific, and quantitative approach to analyse DNA methylation in a variety of frozen or fixed tissues. Moreover, MS-DBA is rapid, easy to perform, and permits the screening of a large panel of samples in one experiment. Thus, MS-DBA can facilitate the routine analysis of DNA methylation in all types of clinical samples.

Molecular genetics of dysplasia in ulcerative colitis.

Numerous molecular genetic events occurring in the development of sporadic colorectal neoplasia have been previously defined. The most frequent genetic alterations are mutations of the APC, KRAS, and TP53 genes, as well as loss of the DCC gene and of the second TP53 allele. The data from several groups indicate that these genes play an important role in ulcerative colitis-associated dysplasias and cancer, as they do in sporadic colorectal adenomas and carcinomas. KRAS and TP53 mutations were detected in dysplasia, but also in villous regeneration and active colitis, and affect a subpopulation of the cells composing these lesions. We conclude that in histologically defined dysplasia, clones can be found that genetically represent precancerous lesions in ulcerative colitis. Seen in this way, part of the active colitis and villous regeneration lesions might be considered as preneoplastic. When present, KRAS mutation is an excellent genetic marker to map populations of preneoplastic cells.

Stability of K-ras mutations throughout the natural history of human colorectal cancer.

We have used a rapid, non-radioactive and sensitive method based on allele-specific amplification using the polymerase chain reaction for the identification of K-ras mutations in archival tissues of colorectal carcinomas. Our purpose was to determine whether or not K-ras mutation provides, when present, a tumour marker throughout the natural history of the disease. We have studied 35 patients who developed recurrent cancer. In 71% of these patients a ras mutation in codons 12 or 13 was observed in the primary tumour. For each of these cases an identical ras mutation was found in the DNA from the local or distant recurrence. In the 29% of cases where no ras mutation was observed in the primary tumour, no newly acquired ras mutation appeared in the recurrent tumour. The time interval between primary tumours and recurrences varied from 3 to 60 months. Our results indicate that K-ras mutation provides a stable tumour marker throughout the natural history of colorectal cancer.

p53 and Ki-ras as prognostic factors for Dukes' stage B colorectal cancer.

Mutations of the TP53 and Ki-ras genes have been reported to be of prognostic importance in colorectal carcinomas. An increased intracellular concentration of the p53 protein, although not identical to, is sometimes seen in tumours with TP53 mutation and has been correlated with poor prognosis in some tumour types. Previous colorectal cancer studies, addressing the prognostic importance of Ki-ras mutation and TP53 aberrations, yielded contradictory results. The aim of this study was to determine in a clinically and therapeutically homogeneous group of 122 sporadic Dukes' B colorectal carcinomas with a median follow-up of 67 months (3-144 months) whether or not p53 protein expression, TP53 mutation and K-ras mutation correlated with prognosis. p53 staining was performed by immunohistochemistry, using the monoclonal antibody DO7 on paraffin-embedded tissue. Mutations in exons 5-8 of the TP53 gene and in codons 12 and 13 of the K-ras gene were assayed in paraffin-embedded tissue by the single-strand conformation polymorphism (SSCP) assay. Nuclear p53 staining was found in 57 (47%) tumours. Aberrant migration patterns indicating mutation of the TP53 gene were found in 39 (32%) tumours. Forty-six carcinomas (38%) showed a mutation of the Ki-ras codons 12 or 13. In a univariate analysis, patients with wild-type TP53 status showed a trend towards better survival, compared with those with mutated TP53 (log-rank test, P = 0.051). Likewise, tumours immunohistochemically positive for p53 showed a worse prognosis than p53-negative tumours (P = 0.010). The presence or absence of mutations in Ki-ras did not correlate with prognosis (P = 0.703). In multivariate analysis, only p53 immunoreactivity emerged as an independent marker for prognosis hazard ratio (HR) = 2.16, 95% confidence interval (CI) 1.12-4.11, P = 0.02). Assessment of p53 protein expression is more discriminative than TP53 mutation to predict the outcome of Dukes' stage B tumours and could be a useful tool to identify patients who might benefit from adjuvant therapy.

Promoter methylation analysis on microdissected paraffin-embedded tissues using bisulfite treatment and PCR-SSCP.

Methylation-sensitive single-strand conformation analysis (MS-SSCA) is a new method of screening for DNA methylation changes. The combination of bisulfite modification and PCR results in the conversion of unmethylated cytosines to thymines, whereas methylated cytosines remain unchanged. This sequence conversion can lead to methylation-dependent alterations of single-strand conformation, which can be detected by SSCA. An analysis of mixtures of methylated and unmethylated DNA at known ratios revealed that the relative intensities of the corresponding bands following MS-SSCA were maintained. MS-SSCA was applied for methylation analysis of human p16 promoter region using genomic DNA obtained from either frozen, fixed, or microdissected fixed tissue sections. MS-SSCA is a rapid, specific, and semiquantitative approach that allows the detection of methylation of the p16 gene promoter. In reconstruction experiments, the method permits the detection of 10% or less of cells harboring a methylated p16 promoter. We have been successful in analyzing by MS-SSCA almost all (96%) tumor samples microdissected from archival paraffin-embedded fixed tissue sections and obtaining reproducible results. In addition, when microdissection was performed, the clonality of this genetic alteration could be identified.

Detection of rare circulating human colon tumor cells in a nude mouse xenograft model.

A highly sensitive allele specific polymerase chain reaction was developed and applied to the detection of K-ras mutation in human colon tumor cells both in the blood and in tissues. An experimental model of human colon carcinoma cells, carrying a GAT mutation in the 12th codon of the K-ras gene, and grafted into nude mice has been selected for evaluating the occurrence of cells in the course of disseminating into the host. We have found tumor cells circulating in the blood starting 37 days following subcutaneous primary implantation. Occasional micrometastatic deposits could be detected in lymph node draining the xenograft, but no tumor cells were found in lungs and mediastinum. In this experimental model, our results indicate that the mere presence of tumor cells in the blood does not imply the full accomplishment of the multi-step metastatic process.

Detection of the synovial sarcoma translocation t(X;18) (SYT;SSX) in paraffin-embedded tissues using reverse transcriptase-polymerase chain reaction: a reliable and powerful diagnostic tool for pathologists. A molecular analysis of 221 mesenchymal tumors fixed in different fixatives.

Synovial sarcoma (SS) is a relatively rare sarcoma, which may be confused with several other mesenchymal and nonmesenchymal lesions. It bears the t(X;18) (SYT;SSX) translocation, which seems to be specific for this tumor type and can be detected in paraffin-embedded tissue, using reverse transcriptase-polymerase chain reaction (RT-PCR). However, the specificity and sensitivity of this detection method have rarely been examined in a large series. Using RT-PCR, we examined 250 mesenchymal and nonmesenchymal, benign and malignant, paraffin-embedded lesions for the SS t(X;18) (SYT-SSX) translocation. PCR products were obtained from 221 tumors (88.5%). There were 135 non-SS tumors, 22 biphasic, and 64 monophasic spindle/round cell SS, of which 10 were cytogenetically confirmed as t(X;18)-positive. SYT-SSX gene fusion transcripts were detected in the SS tumor category only (100% specificity), including 100% of the biphasic SS and 86% of monophasic spindle/round cell SS. Nine tumors originally diagnosed as SS were t(X;18) (SYT-SSX)-negative. Following reassessment, only 3 of these tumors showed clinicopathologic, immunohistochemical, and/or ultrastructural features consistent with that diagnosis, thus raising the overall detection sensitivity to 96%. With regard to the potential adverse effect of the fixatives used, PCR products were obtained in 100%, 91.5%, 90.5%, and 0% of tumors fixed with AFA, buffered formalin, Holland Bouin, and conventional Bouin's fluid, respectively. This study shows that the detection of the SS t(X;18) (SYT-SSX) in paraffin-embedded tissue is feasible with a 100% specificity and an overall 96% sensitivity, provided non-Bouin's fluid fixation is used.

Nuclear accumulation of beta-catenin is a common and early event during neoplastic progression of Barrett esophagus.

Our aim was to characterize expression and mutation of beta-catenin in the progression of Barrett esophagus to adenocarcinoma. Immunohistochemical analysis of beta-catenin was performed on paraffin-embedded tissue from 30 cases with adenocarcinomas and premalignant lesions. To determine whether there is a correlation between beta-catenin nuclear accumulation and exon 3 mutation of this gene, mutational analysis by polymerase chain reaction-single-strand conformation polymorphism was performed on DNA extracted from the same 30 adenocarcinomas. As a result, the prevalence of reduced expression of beta-catenin on the membrane, with or without nuclear staining, increased significantly from low-grade (LG) to high-grade (HG) dysplasia. Focal nuclear staining for beta-catenin was present in 19 cases of adenocarcinoma, and nuclear staining was associated significantly with progression from metaplasia to LG dysplasia. In addition, in glands with clear histologic transition from metaplasia to LG dysplasia, nuclear accumulation of beta-catenin was found only in the LG dysplastic areas. No mutation in exon 3 of the beta-catenin gene was detected in adenocarcinomas. These results demonstrate that disturbance of the APC/beta-catenin pathway, as indicated by nuclear accumulation of beta-catenin, is a common and early event during neoplastic progression in Barrett esophagus.

The natural history of a gastric low grade B cell MALT lymphoma followed during 11 years without treatment.

Low grade B cell mucosa associated lymphoid tissue (MALT) lymphoma of the stomach is usually an indolent tumour that remains localised for a long time before dissemination occurs. MALT appears in the stomach in response to infection by Helicobacter pylori, which is present in 80-90% of cases. The pathogenesis of the evolution from chronic gastritis to malignant lymphoma has not yet been fully explained and the exact role of H pylori in the pathogenesis and progression of gastric lymphoma remains unclear. This report describes the case of a 72 year old woman with a low grade B cell MALT lymphoma localised in the gastric fundus, who refused to be treated for eradication of H pylori. The histological diagnosis of B cell MALT lymphoma was supported by both immunohistochemical and molecular genetic analysis. After 11 years of follow up, this MALT lymphoma remained indolent, without local progression or blastic transformation, and the H pylori infection was still persistent, even though the density of bacteria had decreased drastically. Interestingly, two different clonal immunoglobulin (Ig) gene rearrangements were found in two series of biopsies performed with an interval of 11 years. This case report supports the following notions: (1) H pylori associated gastritis is a risk factor for gastric MALT lymphoma, but might not be sufficient by itself for the progression of the disease, and (2) in the evolution of MALT lymphomas, different cell clones characterised by different Ig rearrangements may emerge.

Synchronous ileal and colonic adenocarcinomas associated with Crohn's disease: report of a case with a focus on genetic alterations and carcinogenesis.

Patients with Crohn's disease have an increased risk of developing intestinal tumours. However, the carcinogenic mechanisms remain poorly understood. To address this question, this report describes an unusual case of Crohn's disease complicated by synchronous small intestinal and colonic adenocarcinomas. Genetic events in both the tumours and their adjacent mucosae were evaluated and the tumorigenesis of these cancers is discussed.

Improved polymerase chain reaction detection of clonal T-cell lymphoid neoplasms.

We have developed and tested a rapid and sensitive method of detecting expansion of T-cell clones using the polymerase chain reaction (PCR) and a single set of consensus primers for the V and J regions to amplify rearranged T-cell receptor-gamma (TCR-gamma) genes. Monoclonality was continued in all of the 18 cases of T-cell neoplasms tested, but not in reactive lymphadenopathy, non-Hodgkin's B lymphomas, and Hodgkin's disease. PCR analysis, using the primer sequence outlined in this study, had an overall specificity of 100% when compared with Southern blot analysis. No false-negative results were observed, certainly owing to the choice of consensus primers and to the control of PCR reactions on agarose gels before testing for clonality by separation of PCR products on polyacrylamide gels. This method for the detection of T-cell monoclonality can be especially useful in cases that are diagnostically problematic with standard histological and immunological analysis and in cases where the material available is limited.

The type of K-ras mutation determines prognosis in colorectal cancer.

BACKGROUND: Mutations involving the oncogene K-ras in colorectal cancer may be related to tumor aggressiveness. However, the value of K-ras gene determination as a prognostic marker has not been clearly established. PATIENTS AND METHODS: The results from 98 patients recruited in a prospective study analyzing the effect of a K-ras mutation as a prognostic factor in colorectal cancer are reported. RESULTS: Disease-free (P = 0.02) and overall survival (P = 0.03) were significantly reduced for patients harboring a K-ras mutation. Two specific mutations demonstrated a significantly increased risk of disease recurrence, namely, 12-TGT (P = 0.04) and 13-GAC substitutions (P = 0.002). Patients with either of these substitutions had a 2-year disease-free survival rate of 37% compared with that of 67% for the group of patients harboring any other mutation type or a wild-type status (P = 0.01). CONCLUSIONS: The results herein presented suggest that K-ras acts as a prognostic factor in colorectal cancer and that this effect is probably related to a limited number of defined mutations.

Detection of malignant effusions: comparison of a telomerase assay and cytologic examination.

Telomerase is inactive in most somatic cells, but has been found to be reactivated in a majority of cancers. Our principal goal was to test whether the presence of telomerase activity concurred with positive cytology, and was thus of potential use in detecting cancer cells in effusions. The telomeric repeat amplification protocol (TRAP) assay and cytological examination were performed in a blinded fashion on 91 unselected effusions, for which laboratory processing was done according to standard procedures. In our series, 30% (27/91) of samples were found to be malignant by cytology. Of these, 19 (70%) were also positive in the TRAP assay. Of the 8 telomerase-negative cytology-positive samples, RNA integrity was generally poor, indicating suboptimal sample conservation for molecular analysis. Negative cytology in the presence of telomerase activity was observed in 17 effusions. Of these, 11 were from patients with advanced cancer, and thus a diagnosis of malignant effusion should be suspected. The TRAP assay for telomerase activity holds promise in the analysis of effusions, but its routine use as an adjunct to cytology awaits further confirmation of its positive predictive value.

Pitfalls in TRAP assay in routine detection of malignancy in effusions.

Telomerase has been found to be reactivated in a majority of cancers but is inactive in most somatic cells. Our principal goal was to determine the potential use of the telomeric repeat amplification protocol (TRAP) assay as marker for malignancy in cytological effusions. The simple selection criterion was the cytological diagnosis, and routine samples were classified into malignant (58 samples) and nonmalignant (233 samples). Of the malignant samples, 44/58 (76%) were positive by TRAP assay. Of the 14 telomerase-negative cytology-positive samples, RNA integrity was poor in 9, indicating suboptimal sample conservation for molecular analysis. In 3 of the remaining 5 samples with a negative TRAP assay, a high number of malignant cells was observed, and these cells might have been telomerase-negative. Thus, the sensitivity of TRAP assay for the presence of malignant cells was about 76%. In the cytologically nonmalignant effusions, the presence of telomerase activity was observed in 24% (55/233). Of these, 6% were highly suspicious for malignancy, 9% were doubtful, and 9% were cytologically nonmalignant effusions confirmed by a follow-up of 12 mo or more. According to these data, the specificity of the TRAP assay to detect tumor cells in effusions ranged only between 82-91%. Our results indicate that, although the TRAP assay is positive in 6-15% of putative malignant effusions, the relatively high number of TRAP false-negative and false-positive cases renders this test unsuitable for routine diagnostic purposes.

[A comparative study on p53 gene mutation in primary human Dukes C colon cancer with that in matched lymph node metastasis].

OBJECTIVE: To study the relationship between metastasis of colon cancer and the mutation of p53 gene. METHODS: PCR-SSCP was used to analyse exon 5-9 of the p53 gene in 73 cases of Dukes C human primary cancer and 40 cases of matched lymph node metastasis. RESULTS: Mutations were identified in 27 of 73 primary cancers (37%) and 19 of 40 lymph node metastasis (47.5%) with the overall incidence of p53 mutation being 44%. In 21 of 40 cases in which both primary and metastatic cancers were analysed by SSCP, we found no p53 mutations in both lesions. While the same exon and exactly the same mutated band pattern could be seen both in primary and metastatic cancers in another 12 cases (30%). In addition, the agreement of p53 mutation status in primary cancer to the lymph node metastases was lost in the remaining 7 cases (17.5%). All of the 7 cases were confirmed to have base substitution mutations by DNA direct sequencing. In 5 of 7 individuals, the point mutations were detected only in lymph node metastases but not in the primary cancers and in 2 of 7 cases, two exons were found to have mutations in lymph node metastases while only one or no mutation was identified in the primary cancers. CONCLUSION: Most p53 mutations occurred before metastasis and p53 mutations persist throughout the final stage of the progression and metastasis in colon cancer. Furthermore, the metastasis of colon cancer is accompanied by the emergence of new mutation in p53 gene or metastasis is selected against the p53 mutation, which suggests that the mutations in p53 gene may be related to the metastasis of colon cancer.