Loss of heterozygosity at 3p23 is correlated with poor survival in patients with colorectal carcinoma.

BACKGROUND: Loss of heterozygosity (LOH) of chromosome 3p has been observed commonly in carcinomas of various tumor tissues, including colorectal carcinoma (CRC). Because there is no report analyzing 3p deletions in relation to patient prognosis in CRC, the authors investigated the prognostic value of LOH on 3p in 87 patients with sporadic CRC. METHODS: DNA samples from tumor and nontumor tissues were amplified by using polymerase chain reaction (PCR) and were analyzed for LOH on 3p using four different polymorphic human dinucleotide repeat DNA markers that map on this chromosome arm. The correlations with prognosis were established by the Kaplan-Meier method, and the Cox proportional hazards model was used to identify which independent factors jointly had a significant influence on patient survival. RESULTS: Overall, allelic losses were detected in 19.5% of the patients evaluated. Only considering informative tumors, the data indicated that LOH was observed in 17 of 71 (29.4%) informative cases. Results from survival analysis showed a significant correlation between this molecular abnormality and both overall survival and disease free survival (P = 0.02 and P = 0.0005, respectively). The worst prognosis was found for the group of patients with LOH at 3p23: This alteration was an independent prognostic factor according to Cox multivariate analysis. CONCLUSIONS: This study is the first to demonstrate the prognostic significance of LOH at chromosome arm 3p for patients CRC and may help to identify patients who need an intensive postoperative follow-up protocol.

Detection of telomerase activity in human carcinomas using a trap-ELISA method: correlation with hTR and hTERT expression.

We have evaluated telomerase activity in a tumour population of 65 human cancers by using a TRAP-based method, in which detection is performed by an enzyme immunoassay (ELISA). We have corroborated that sensitivity and specificity of this new procedure can be considered similar to that of classical TRAP method, having the advantage of a rapid and reproducible analysis of large pools of samples. Thus, telomerase activity was detected in 83% of the tumours included in our population. Moreover, we found a significant association between enzyme activity and both hTR and hTERT expression (P=0.004 and P=0.04, respectively).

DNA amplification on chromosome 6p12 in non small cell lung cancer detected by arbitrarily primed polymerase chain reaction.

Gene amplification is clearly an important aspect of tumour growth and development and has prognostic significance in certain tumours. The identification and genetic characterisation of new areas of amplification in human malignancy remains an important goal in understanding the underlying genetic lesions within these tissues. In the present work, arbitrarily primed-PCR (AP-PCR) has been applied to detect and characterise amplified DNA fragments in human non small cell lung cancer (NSCLC). Our results show that gains of genomic sequences occur at high frequency (64% of all genomic changes analysed). Moreover, we succeeded in detecting a genomic sequence that is highly amplified in one of the tumours analysed. The amplification intensity of this DNA fragment was also increased in 29 (45%) of the 65 NSCLC patients from our study. The amplified DNA fragment was isolated and identified as a 600 bp sequence mapped to chromosome 6p12. This sequence did not show significant homology with known human DNA sequences. Interestingly, a gene related to cancer processes, the pim-1 oncogene, is placed neighbouring to this region on chromosome 6. Survival studies revealed that disease-free interval of NSCLC patients was shorter in patients bearing the amplified sequence (p = 0.05 by the Breslow test). Our findings suggest that the amplified sequence located on chromosome 6 might be relevant in the pathogenesis of human NSCLC. Int. J. Cancer (Pred. Oncol.), 84:344-349, 1999.

Differential prognosis of replication error phenotype and loss of heterozygosity in sporadic colorectal cancer.

Several distinct genetic alterations have been associated with colorectal tumorigenesis. This study investigated the frequency of microsatellite instability, also known as replication error (RER), and loss of heterozygosity (LOH) at six chromosome regions in sporadic colorectal cancer (CRC). Eighty-six tumour and paired normal mucosa samples were included in the study. A polymerase chain reaction (PCR)-based technique was performed to analyse six (CA)n dinucleotide repeats located near or within regions containing important genes implicated in the complex process of colorectal tumorigenesis (chromosomes 2p, 3p, 5q, 11p, 17p and 18q). Overall, LOH frequency was higher in RER-tumours (25/46, 54.3%) compared with RER+ tumours (9/40, 22.5) (P = 0.04). To investigate prognostic implications, survival analysis was performed for 66 patients. Compared with RER- tumours, patients with RER+ tumours at 2p, 3p, 5q, 11p or 18q were found to have an improved prognosis (overall survival, P = 0.02 and disease-free survival (DFS) P = 0.005) this variable being an independent prognostic factor by multivariate analysis (P = 0.001). Overall survival of patients whose tumours were LOH+ was significantly shorter compared with those without LOH (overall survival, P = 0.008 and DFS, P = 0.01). Thus, tumours displaying RER+ and LOH+ phenotype, as established by microsatellite analysis, show a differential prognosis. These data indicate that this may be a useful tool for the identification of patients at different risks affected by CRC.

Genetic abnormalities and microsatellite instability in colorectal cancer.

Our purpose was to investigate different genetic abnormalities, such as K-ras mutations, p53 alterations, and c-myc RNA overexpression, as well as microsatellite instability in 63 colorectal tumors obtained from patients that had undergone surgery. K-ras point mutations were analyzed by PCR-RFLP technique, followed by sequencing; p53 protein accumulation by immunohistochemistry; p53 gene mutations in exons 5-9 were studied by the SSCP and sequencing techniques, and c-myc overexpression by Northern blot. Microsatellite instability was performed at chromosomes 2p, 3p, and 11p by a PCR-based technique. Our data indicate a trend toward a poorer prognosis in patients who had K-ras transversions; besides, we have obtained a prevalence of c-myc RNA overexpression and p53 exon 7 mutations in the latest stages of tumor progression. In conclusion, our findings suggest that the recognition of molecular abnormalities might be used in colorectal cancer as a prognostic indicator or to determine the metastatic potential of colorectal adenocarcinomas.

Prognostic value of genomic damage in non-small-cell lung cancer.

Genomic alterations have been analysed in 65 non-small-cell lung cancer (NSCLC) tissue samples by using the arbitrarily primed polymerase chain reaction (AP-PCR), which is a PCR-based genomic fingerprinting. We have shown that AP-PCR may be applied as a useful and feasible practical method for detection of the genomic alterations that accompany malignancy in NSCLC. Genomic changes detected by us consisted of: allelic losses or gains in anonymous DNA sequences, homozygously deleted DNA sequences and polymorphic DNA sequences. According to these genomic changes, lung tumours evaluated in the present study have been scored into three groups: low, moderate and high genomic damage tumours. The aim of this study was to investigate the effect of genomic damage on patient survival. Survival analysis was carried out in 51 NSCLC patients. Our results revealed that high genomic damage patients showed a poorer prognosis than those with low or moderate genomic damage (P = 0.038). Multivariate Cox regression analysis showed that patients with higher genomic alterations displayed an adjusted-by-stage risk ratio 4.26 times higher than the remaining patients (95% CI = 1.03-17.54). We can conclude that genomic damage has an independent prognostic value of poor clinical evolution in NSCLC.