p53 mutations in relation to human papillomavirus type 16 infection in squamous cell carcinomas of the head and neck

The relationship between human papillomavirus (HPV) type 16 infection and p53 gene mutations was investigated in squamous cell carcinomas of the head and neck (SCCHN). HPV was detected by general primer-mediated and type-specific PCR. Alterations in the p53 gene were investigated using single-strand conformation polymorphism and sequence analysis in 27 SCCHN, of which 12 were HPV 16-positive and 15 were HPV-negative. Mutations were detected in 2/12 (16.7%) HPV 16-positive and 7/15 (46.7%) HPV-negative tumours; this difference was not statistically significant. The predominant mutations were deletions and C --> T transitions; G --> T transversions were found in only 2 tumours. Our results indicate that the presence of HPV 16 and p53 mutations is not mutually exclusive and detection of a p53 mutation does not exclude a potential role for HPV 16 in the pathogenesis of a subset of SCCHN.

p53 gene aberrations in non-small-cell lung carcinomas from a smoking population

We examined 46 non-small-cell lung carcinomas (NSCLCs) for the presence of p53 mutations in exons 4-9, positive p53 immunostaining and loss of heterozygosity (LOH) in the TP53 locus. p53 mutations were detected in 13 tumour samples (28.3%), whereas overexpression of the p53 protein was found in 30 of 45 (67%) samples. Allelic loss was found in 9 of 38 (23.6%) informative cases. The statistical analysis revealed no significant correlation between p53 mutations and clinicopathological data, although mutations appear to occur more frequently in squamous cell carcinomas (7 of 18) than in adenocarcinomas (2 of 15). All but three individuals in this study group smoked. In contrast to previous reports, we found a higher prevalence of GC-->AT transitions than of GC-->TA transversions, as expected in a smoking population. A trend was found between p53-positive immunostaining and a history of heavy smoking (76-126 pack-years) and was inversely correlated with allelic deletion (LOH) at the TP53 locus. Eight of the 12 NSCLCs containing p53 mutations also had concomitant p53 overexpression, and it is of specific note that three of the four tumours containing p53 'mutations' with no overexpression of the p53 protein had either insertions or deletions in the p53 gene. No correlation was found between p53 mutations and fractional allele loss or ras mutations. p53 mutations in this Merseyside population in the UK do not appear to be as common as in other reports for NSCLC and exhibit predominance of GC-->AT transitions preferentially at non-CpG sites, suggesting that other carcinogens in addition to those in tobacco smoke may be involved in NSCLC in the Merseyside area of the UK.

Codon 12 ras mutations in patients with myelodysplastic syndrome: incidence and prognostic value

To determine the prevalence of activated rasoncogenes (N-ras, Harvey-ras Kirsten-ras), DNA derived from peripheral blood of 51 patients with myelodysplastic syndrome (MDS) was investigated. The method was based on the polymerase chain reaction (PCR) technique to amplify DNA, followed by restriction fragment length polymorphism (RFLP) analysis. Among the French-American-British (FAB) subtypes, N-ras mutations were found in two patients with refractory anemia with excess of blasts (RAEB), in one patient with refractory anemia with excess of blasts in transformation (RAEB-t), and in two patients with chronic myelomonocytic leukemia (CMML). MDS patients with a mutation at codon 12 of the N-ras gene showed shorter survival duration than other MDS patients of the same FAB subtypes, although these findings proved to be not statistically significant (P > 0.1). Interestingly, all but one patient with N-ras mutation developed acute myelogenous leukemia (AML). In conclusion, the presence of mutation at codon 12 of the N-ras gene might serve as a negative prognostic factor at diagnosis of MDS.

Fractional allele loss data indicate distinct genetic populations in the development of non-small-cell lung cancer

Allelic imbalance or loss of heterozygosity (LOH) has been widely used to assess genetic instability in tumours, and high LOH on chromosome arms 3p, 9p and 17p has been considered to be a common event in non-small-cell lung cancer (NSCLC). We have investigated allelic imbalance in 45 NSCLCs using 92 microsatellite markers on 38 chromosome arms. LOH of 38% was observed on 3p using nine markers, 58% on 9p using 15 markers and 38% on 17p using five markers. Fractional allele loss (FAL) has been calculated for each tumour (FAL is the number of chromosome arms showing LOH/number of informative chromosome arms) and a median FAL value of 0.09 was obtained in the 45 NSCLCs studied. The LOH data were examined on the basis of FAL scores: low FAL (LFAL) (0.00-0.04), medium FAL (MFAL) (0.05-0.13) and high FAL (HFAL) (0.14-0.45) based symmetrically around the median FAL value of 0.09. Tumours with HFAL values showed a very clear polarisation of the LOH data on chromosome arms 3p, 9p and 17p, such that 80% showed loss on 3p, 80% on 9p and 73% on 17p. These incidences of LOH were significantly higher than would be expected, since overall genetic instability in these HFAL tumours ranged from 14% to 45% LOH. Nine of the 14 patients in the LFAL group were found to have no LOH on 3p, 9p or 17p, but five of these had LOH at other sites: i.e. LOH on 5p, 5q, 8p, 13q, 16q and 19q. These results indicate that LFAL patients form a new subset of NSCLC tumours with distinct molecular-initating events, and may represent a discrete genetic population.

Polymorphisms in the promoter region of the WAF1/CIP1 gene

The WAF1/CIP1 gene encodes p21(waf1), a CDK inhibitor which is implicated in cell growth arrest and differentiation, and is activated by wild-type p53. We examined the presence of mutations in a part of the 5' flanking region which is known to contain p53 binding sites, in 50 cases of lung cancer and 11 individuals with no history of cancer. Polymorphisms were identified in the region close to: but not within, the p53 binding sites. The first polymorphism occurred at nucleotide -2203 prior to the transcription start site, four base pairs upstream of a p53 binding site and created an MscI restriction site. The second polymorphism was more complex and included four sites (nucleotides -1463, -1526, -1533 and -1594). Two patterns (alleles) were identified for this region. These polymorphisms were observed at similar percentages in DNAs from lung cancer patients and individuals who had no history of cancer. A computer transcription factor motif analysis showed that these polymorphic sites are homologous (>85%) to consensus sequences of transcription factors such as ETS-1, Elk-l, GATA-1 and AP4 but their role in the regulation of p21(waf1) expression is still unclear. This is the first report of polymorphisms in this region of the WAF1/CIP1 promoter.

Inducible h-ras gene-expression controlled by an allosterically regulated transactivator

Inducible promoters have been employed widely to control the transcription of specific genes and thus to elucidate their role. We constructed a plasmid in which three lac operator sequences and the SV40 early promoter were placed upstream of the T24 H-ras1 gene. This plasmid was co-introduced in rat fibroblasts with a plasmid coding for a fusion protein containing the DNA binding domain of the lac repressor protein and the transactivation domain VP16 from HSV1. In the clones derived from this co-transfection, the transcription of the exogenous H-ras1 gene is dependent on the interaction between the transactivator protein and the lac operators. Given that this interaction is inhibited by IPTG, such a cell line overexpresses the H-ras gene encoded protein ras p21 and the addition of isopropyl beta-D-thiogalactopyranoside (IPTG) into the culture medium diminishes overexpression. The decrease of ms expression levels after the addition of IPTG was confirmed by Western blot analysis and by quantitative Reverse Transcription PCR based on comparison of amplification levels between the target cellular H-ras1 gene transcript and an in vitro produced deletion mutant H-ras reference transcript.

Detection of human cytomegalovirus by the polymerase chain-reaction in immunosuppressed and immunocompromised patients

Infections caused by Human Cytomegalovirus (HCMV) are very common in patients who undergo immunosuppression or immunocompromisation. The techniques used for routine HCMV detection are time-consuming and lack specificity and sensitivity. The ability of the Polymerase Chain Reaction (PCR) to amplify HCMV DNA from clinical samples of the patients is a valuable diagnostic tool for the detection of HCMV in the early stages of the infection. We used a pair of primers to amplify a 435 bp region of the immediate early-1 gene, to detect HCMV DNA in clinical samples from patients at high risk for HCMV infection. We found HCMV in the following type of patients: 6 out of 20 in immunosuppressed, 11 out of 31 in immunocompromised, 5 out of 8 in pregnant women, 4 out of 25 in patients with high anti-CMV IgM and IgG titres, 1 out of 2 in patients with kidney failure, and 6 out of 14 in patients with opthalmic disorders. Sixty-seven specimens, which were found to be negative for CMV by the PCR technique, were used to inoculate human fibroblast monolayer cultures and PCR was performed to the DNA extracted from the cultured cells. Only in 1 out of the 67 cases HCMV DNA was detected.

Detection of the cytomegalovirus by the polymerase chain reaction DNA amplification in a kidney transplanted patient

Cytomegalovirus injection is common in kidney transplanted patients. Viremia is the only marker of active CMV infection, but the use of cell culture for the direct detection of the virus is time-consuming and not very sensitive, while the detection of CMV by measuring the titre of antibodies is difficult due to the immunosuppression these patients undergo. Thus the ability to amplify CMV DNA by the polymerase chain reaction from blood or urine samples of the patients becomes a valuable diagnostic tool for the detection of CMV in the early stages of the infection. Using a set of primers specific for the amplification of a 435 bp region of the IE-1 gene, we detected CMV DNA in blood leucocytes of a kidney transplanted patient who received the transplant from a CMV-seropositive donor, 45 days after the operation, while the antibody titre showed no evidence of active CMV infection.

Detection of hepatitis-B virus-DNA and mutations in k-ras and p53 genes in human hepatocellular carcinomas

Hepatitis B virus (HBV) infection is considered as one of the major risk factors in the development of human hepatocellular carcinoma (HCC). Recent studies have also suggested the implication of oncogene and onco-suppressor genes in liver carcinogenesis. We studied 41 cases of HCC for the presence of HBV DNA and point mutations in codon 12 of K-ras and codon 249 of p53. We used 'nested' PCR for the amplification of HBV because of the expected low incidence of the virus DNA in the samples. PCR was also used for the amplification of K-ras and p53 regions that contain the codons of interest, followed by RFLP analysis for the detection of point mutations. HBV DNA was amplified in 22 cases (53.7%), while 5 cases (12.2%) appeared to carry mutations in codon 12 of K-ras and 7 cases (17.1%) had mutations in codon 249 of the p53 gene. These results further support the correlation between HBV infection and HCC and also indicate an implication of K-ras and p53 genes in hepatocarcinogenesis.

Prognostic significance of oncogenes and tumor suppressor genes in human malignancy

Recent progress in the field of oncogenes has produced valuable information concerning the molecular and cellular biology of the cancer cell and provided a tool to investigate the process of carcinogenesis. Some oncogenes such as the ras, myc, erbB-2 and abl have been extensively investigated in the progression of carcinogenesis in several types of human tumors. The p53 tumor suppressor gene has recently been shown to play the role of "molecular policeman," and is obviously important in the development of many tumors, as mutations in this gene are the most common genetic abnormalities found in all neoplasias. In certain cases the incidence of aberrant gene expression and genetic alterations of oncogenes and tumor suppressor genes have been shown to be important in the progression of these cancers and may be of use as prognostic indicators and form the basis for a successful therapy.

H-ras oncogene mutations in the urine of patients with bladder-tumors - description of a noninvasive method for the detection of neoplasia

Bladder cancers are usually curable, by surgical or transurethral excision, if diagnosed at an early stage. Tumor derived mutations in oncogenes potentially provide specific markers for the detection of surgically resectable tumors. The detection of point mutations of H-ras oncogene correlated with this disease. DNA sequences produced by the Polymerase Chain Reaction (PCR) can be considered for this application, because theoretically bladder tumors should shed cells containing this mutation into the urine. We examined urine from 21 individuals with bladder cancer before any treatment, as well as tissue specimens from the excised tumor and we found 10 mutations of the H-ras gene at codon 12 in the urine (47.61%) and 14 mutations in the tumor specimens (66.66%). We were able to detect nearly 50% of the patients with bladder tumors using this method. We also studied two relapses; in one case (which presented the mutation in the original tumor and the urine) the relapse grade had progressed from II to III. In the other case the relapse grade stayed at III but it presented for the first time the studied mutation in the urine. These results provide the theoretical and technical basis for the detection of bladder tumors by a non-invasive method and possibly for the evaluation of the invasiveness of the disease.