Low prevalence of human papillomavirus in a geographic region with a high incidence of head and neck cancer

BACKGROUND: The main purpose of this study was to determine the prevalence of human papillomavirus (HPV) infection in patients with head and neck carcinomas from Brazil. MATERIALS AND METHODS: Forty-five patients with head and neck squamous cell carcinoma were included in the study, from 1995 to 1996. Forty-two were male and 3 female, with age ranging from 32 to 82 years (median 61). Five patients (11%) did not have previous history of use of tobacco and 38 (90.5%) were heavy smokers. Tumor sites were pyriform sinus, 10; tongue, 11 (oral, 6; base, 5); larynx, 7; floor of mouth, 3; tonsil, 6; retromolar area, 3; inferior gingiva 2; buccal mucosa, 2; and maxillary sinus in 1 patient. Twenty-five were stage IV, 17 stage III, and 3 stage II. RESULTS: The presence of HPV DNA was detected in 5 of 45 patients (11%), all of them with HPV 16. Two patients had HPV DNA in normal mucosa and tumor tissue, 1 patient had HPV DNA only in the normal mucosa and tumor tissue, 1 patient had HPV DNA only in the normal mucosa, and 2 patients were positive for HPV DNA in tumor tissue. Four patients were male and 1 was female; 2 patients were nonsmokers. Three patients had tonsil carcinoma, 1 patient had a tongue carcinoma, and 1 patient had a pyriform sinus cancer. CONCLUSIONS: The role of chemical carcinogens seems to be more important in the genesis of head and neck cancer than is HPV infection. The presence of HPV DNA in 5 of 45 patients stimulates further investigation to determine the role of HPV as a risk factor for head and neck carcinoma.     

Relationship between human papillomavirus E7 protein and Rb gene product in fresh tissues of squamous cervical carcinoma

OBJECTIVE: To study the possibility of complex formation of the E7 protein encoded by human papillomavirus (HPV) binding to retinoblastoma gene product (pRb) in fresh samples of squamous cervical carcinoma (SCC). METHODS: HPV 6/11, 16, 18, 33 DNA were detected in 40 samples of by polymerase chain reaction technique (PCR). The complexes of HPV E7-pRb were examined in fresh tissues of HPV contained SCC through capture enzyme linked immunosorbent assay (capture-ELISA). RESULTS: 45.0% (18/40) of the samples were proved to be HPV positive by PCR. Out of 18 samples with HPV positive samples, the complexes of HPV E7-pRb were detected in 9 cses, including 1 HPV18 positive and 8 HPV16 positives. The complexes of HPV E7-pRb were not found in 2 cases of positive HPV 6/11. No correlation was observed between the E7 protein binding to pRb and the histological grade of cervical carcinoma (P < 0.05). There was correlation with clinical staging, the number of cases showing that the E7 protein pRb complex in stage I was significantly higher than that in stages II-IV (P < 0.05). CONCLUSIONS: The complex of "high risk" HPV E7-pRb was demonstrated in fresh tissues of SCC. There is no correlation between the complex and histological grade of SCC. The complex formation may occur in the early developmental stage of cervical cancer.     

Detection and typing of human papillomavirus in cervical specimens of Turkish women

The DNA in situ hybridization (DISH) and conventional solution phase polymerase chain reaction (PCR) were applied to identify human papillomavirus (HPV) DNA in cervical specimens of Turkish women. Samples consisted of 21 cervical brushings from pregnant women and 20 paraffin-embedded biopsies from women with condylomatous or dysplasic lesions. It was found that two out of 21 (9.5%) pregnant women were harbouring HPV-DNA detected by PCR. One woman was infected with HPV 16/30's and the other with an unidentified type. As for the biopsy specimens, the rate of HPV-DNA positivity was 30% and 45% by DISH and PCR, respectively. A double infection was observed in more than 50% of the positive cases. Moreover, HPV 18 was never detected. The results indicated that HPV-DNA is rarely present in cytomorphologically normal smears from pregnant women. The PCR method was successfully adapted for HPV typing in clinical lesions which simultaneously contained different HPV sequences.     

Effect of nonsteroidal anti-inflammatory drugs on the action of misoprostol in a regimen for early abortion

BACKGROUND AND OBJECTIVES: Because warts are often found in the male urethra, human papillomavirus (HPV) may well be present in urine of patients with urethral condylomata. GOAL: To detect HPV DNA in urine specimens of men with condylomata acuminata using polymerase chain reaction. STUDY DESIGN: Forty-seven urine specimens and 25 paraffin-embedded tissues of condylomata acuminata were obtained from men. Of the 47 urine specimens, 29 were from patients with urethral condylomata, 3 from patients with penile condylomata only, and 15 from control subjects without condylomata. Both L1 consensus primers and type-specific primers for-HPV 6, 11, 16, 18, and 33 were used. RESULTS: HPV DNA was detected in 22 of the 29 (76%) urine specimens from patients with urethral condylomata, in none of the 3 urine specimens from patients with penile condylomata, and in none of the 15 controls. Paraffin-embedded tissues of all 25 condylomas were positive for HPV DNA. The HPV types detected in urine were identical to those detected in urethral condylomas. CONCLUSIONS: HPV DNA is present in urine of patients with urethral condylomata. Urine may be used for noninvasive screening of asymptomatic HPV infections of the male genital tract. Detection of HPV DNA in urine may be useful for monitoring the response to treatment of urethral condylomata.     

Crystallization of free aspartate aminotransferases from polyethylene glycol solution

Human papillomavirus (HPV) is associated with benign cutaneous or mucosal lesions and with malignant tumours, but none of the HPV types has so far been related to skin tags. Skin biopsy specimens from 49 Caucasian patients suffering from the presence of multiple soft fibromas were analysed by means of dot blot hybridization and by polymerase chain reaction assays aimed at detecting all known HPV types. The results revealed the presence of HPV DNA type 6/11 in 88% of the skin tags examined. This result supports the hypothesis that HPV plays a part in the progression of cutaneous soft fibromas, as previously reported for laryngeal papillomas.     

Detection of human papillomavirus in routinely processed biopsy specimens from laryngeal papillomas: evaluation of reproducibility of polymerase chain reaction and DNA in situ hybridization procedures

The frequency of human papillomavirus (HPV) in laryngeal papillomas varies largely among different studies. DNA in situ hybridization (ISH) has been the most widely used method for detection of HPV. The aim of this study was to compare the reproducibility and sensitivity of ISH with polymerase chain reaction (PCR) in 35 specimens of laryngeal papillomas routinely fixed in buffered or unbuffered formalin. Out of 12 specimens fixed in buffered formalin, 10 were positive for HPV 6/11 using ISH. The procedure was repeated three times and three specimens were positive only twice. Nine biopsies were positive for HPV using PCR with consensus primers (My 09/11) on dewaxed tissue without extracting DNA. In three repeated PCRs, the results were inconsistent in three samples. After DNA extraction, all 12 samples were positive with PCR. Of the 23 specimens fixed in unbuffered formalin, 14 were HPV-positive with ISH, while only one was positive with PCR. We concluded that PCR with My 09/11 consensus primers is a highly sensitive method for detection of HPV in laryngeal papillomas fixed in buffered formalin, but useless for samples fixed in unbuffered formalin. When DNA was extracted from the former type of fixed tissue, the results were highly reproducible. In contrast to PCR, ISH appeared to be less influenced by fixation procedure, but it was not as reproducible and sensitive as PCR. Negative results did not necessarily mean absence of HPV.     

Effect of age on synaptic size in human brain tissue proximal to tumor masses

The objective of this study was to evaluate the incidence of residual disease and the presence of human papillomavirus (HPV) after conization. Data on 53 patients with carcinoma in situ or microinvasive carcinoma who underwent hysterectomy less than 2 months after conization were examined. Seven of 53 patients (13%) had positive margins. In 4 of these 7 patients (57%), residual disease was found in the postconization hysterectomy specimen. Two of 46 patients (4%) with negative margins also had residual disease. HPV DNA was detected by PCR in 27 of 53 conization specimens and in 2 postconization hysterectomy specimens. Of 2 patients, 1 did not have residual disease. Residual disease could be present even with a negative conization margin, and HPV DNA may be found in a histologically normal cervix after conization.     

Detection of human papillomavirus DNA sequences in oral squamous cell carcinomas and their relation to p53 and proliferating cell nuclear antigen expression

BACKGROUND: The etiology of oral squamous cell carcinoma (SCC) is still obscure. Since human papillomavirus (HPV) DNAs are associated with carcinoma of the uterine cervix, carcinomas of the oral cavity were investigated to ascertain if these viruses are present in squamous carcinomas of this anatomic site. METHODS: Seventy-seven oral mucosal SCCs were examined for the presence of HPV DNAs by polymerase chain reaction and dot blot hybridization. Immunohistochemical detection of proliferating cell nuclear antigen (PCNA) and p53 was performed and single strand conformation polymorphism analysis for p53 was undertaken. In situ hybridization detection of HPV-16 DNA also was performed. RESULTS: Human papillomavirus-16 DNA was detected in 23 cases of oral SCC and both HPV-16 and HPV-18 DNA were detected in one case of tongue SCC. Human papillomavirus DNAs were detected of 11 of 33 tongue, 4 of 15 gingival, 2 of 4 palate, 2 of 5 buccal mucosa, 3 of 7 maxillary sinus, and 2 of 11 the floor of the mouth SCCs. None were detected in SCCs of the retromolar region (0/2). Immunohistochemical examination for p53 was performed in 26 cases of oral SCC and the accumulation of p53 protein was observed in 6 cases (i.e., in 4 of 17 HPV DNA-negative cases and in 2 of 9 HPV DNA-positive cases). Single strand conformation polymorphism analysis confirmed gene mutations in all 6 cases. Human papillomavirus-16 DNA was predominantly identified in cancer cells that showed a morphologic resemblance to basal cells and its hybridized signal in keratinized cells was reduced by in situ hybridization detection. Immunohistochemical detection of PCNA revealed its cooccurrence with HPV-16 DNA in cancer cells. CONCLUSIONS: These results suggest that HPV-16 DNA sequences may have the capability to maintain the proliferative state of epithelial cells, and may contribute to the production of malignant phenotypes.     

Expression of Ets-1 transcription factor in relation to angiogenesis in the healing process of gastric ulcer

Psoralen and UVA (PUVA) photochemotherapy is associated with a dose-dependent increased risk of nonmelanoma skin cancer in patients treated for psoriasis. Like ultraviolet B radiation, PUVA is both mutagenic and immunosuppressive and may thus act as a complete carcinogen; however, the reversed squamous to basal cell carcinoma ratio (SCC:BCC) in PUVA-treated patients, also seen in immunosuppressed renal transplant recipients, suggests a possible cofactor role for human papillomavirus (HPV) infection. In this study we examine a large series of benign and malignant cutaneous lesions for the presence of HPV DNA from patients treated with high dose (> or =500 J per cm2) ultraviolet A. A panel of degenerate primers based on the L1 (major capsid protein) open reading frame was employed, designed to detect mucosal, cutaneous, and epidermodysplasia verruciformis HPV types with high sensitivity and specificity. HPV DNA was detected in 15 of 20 (75%) non-melanoma skin cancer, seven of 17 (41.2%) dysplastic PUVA keratoses, four of five (80%) skin warts, and four of 12 (33%) PUVA-exposed normal skin samples. The majority of HPV positive lesions contained epidermodysplasia verruciformis-related HPV including HPV-5, -20, -21, -23, -24, and -38. Possible novel epidermodysplasia verruciformis types were identified in further lesions. Mixed infection with epidermodysplasia verruciformis, cutaneous, and/or mucosal types was present in six of 30 (20%) of all HPV positive lesions, including in normal skin, warts, dysplastic PUVA keratoses, and squamous cell carcinomas. The prevalence and type of HPV infection in cutaneous lesions from PUVA-treated patients is similar to that previously reported in renal transplant-associated skin lesions, and suggests that the role of HPV in PUVA-associated carcinogenesis merits further study.     

Randomized, double-blind, placebo-controlled study of ascorbate on the preventive effect of nitrate tolerance in patients with congestive heart failure

Mitogen-activated protein kinase (MAPK) is a serine-threonine kinase that is activated by various extracellular stimuli. Extracellular signal-regulated kinases (ERK1 and ERK2), an MAPK subfamily, are activated by many oncogenes, such as ras and raf, and they induce cell proliferation. myc is also an oncogene and one of the targets of ERKs. Mutations of ras and overexpression of myc were found in various human cancers, and ERKs were also reported to play a role in carcinogenesis. In this study, we examined 39 biopsy specimens of oral squamous cell carcinoma (OSCC) and 5 of normal gingival mucosa for the expression of ERK protein and the proliferation marker, MIB-1 (Ki-67 antibody). Thirteen OSCC specimens and five normal gingival biopsies were also examined for the expression of ERKs mRNA by in situ hybridization. Double staining for ERKs and MIB-1 was also performed. Histologically, 18 patients (46%) were diagnosed with well-differentiated SCC, 17 (44%) with moderately differentiated SCC, and 4 (10%) with poorly differentiated SCC. The histologic grade correlated with the MIB-1 index. The localization of ERK1 was similar to that of ERK2. Positive signals for ERK proteins were localized in superficial keratinocytes in normal gingival mucosa, whereas these mRNAs were weakly positive in the basal and spinous layer. Basal and suprabasal cells were positive for MIB-1. In well-differentiated and moderately differentiated OSCC, positive signals for ERK mRNA and proteins were found at higher levels than in normal gingival mucosa in keratotic cells around cancer pearls. Some cells showed positive signals for ERKs and MIB-1. Furthermore, most cancer cells in poorly differentiated SCC were positive for both ERK and MIB-1. The histologic grade was statistically related to the percentage of cells positive for both ERK and MIB-1. This suggested that ERKs might be related to proliferation in OSCC.     

Anatomic variants of the internal carotid artery as differential parapharyngeal space-occupying lesions diagnosis

AIMS: To study the prevalence of high risk oncogenic human papillomaviruses (HPV) in inverted papilloma and papillary transitional cell carcinoma of the bladder. METHODS: Ten cases of inverted papilloma and 20 cases of papillary transitional cell carcinoma of the bladder from Chinese patients in Hong Kong were examined for the presence of HPV type 6, 11, 16, 18, 31, and 33 genomes using the polymerase chain reaction and HPV type specific primer probe combinations on paraffin wax embedded biopsy specimens. RESULTS: Of the 10 cases of inverted papilloma, cases 1 and 6 showed the presence of HPV types 16 and 18, respectively. Six of the 20 papillary transitional cell carcinomas were positive for HPV type 18. The other HPV types were not detected. CONCLUSIONS: HPV type 18 was found in 60% and 30% of cases of inverted papilloma and papillary transitional cell carcinoma of the bladder, respectively. These tumours were rarely associated with HPV types 6, 11, 16, 31, and 33. The role of HPV type 18 in oncogenesis of inverted papilloma and transitional cell carcinoma of the bladder requires further studies.     

Human papilloma virus and p53 in head and neck cancer: clinical correlates and survival

Recent studies have shown that p53 mutations are frequently found in cancer of the head and neck, whereas others have indicated that human papilloma virus (HPV) infection may be involved. Thus far, no studies have examined both p53 and HPV in the same patient population and correlated the results with clinical characteristics and outcome. The purpose of this study was to examine any interrelationship between p53 and HPV in patients with squamous cell carcinoma (SCC) of the head and neck. We also planned to correlate the experimental findings with clinical characteristics, known risk factors, and treatment outcome to determine whether any prognostic factors could be detected. Archival material from 66 patients with SCC of the head and neck were selected for study based on the availability of tissue from the primary tumors prior to treatment. A data base was constructed containing all clinical parameters at the time of diagnosis and risk factors. Genomic DNA was isolated and amplified using PCR, followed by SSCP analysis and direct genomic sequencing of all variants to detect p53 mutations. Two independent methods were used for HPV detection: (a) PCR amplification using primers homologous to the E6 region of HPV 16, 18, and 33, followed by RFLP analysis; and (b) PCR amplification with HPV L1 consensus primers, followed by triple restriction enzyme digestion. The results were entered into the data base for statistical analysis. Twenty-four percent of patients were found to have p53 mutations, and 18% were positive for HPV infection. Only one patient was positive for both. Tonsilar cancer was strongly correlated with HPV (P = 0.0001) and inversely correlated with p53 (P = 0.03). The only clinical parameter associated with p53 mutation was a trend toward a heavier smoking history. A subset analysis of the patients with tonsilar cancer revealed inverse correlations with smoking (P = 0. 015) and alcohol use (P = 0.05). Also, white patients with SCC of the tonsil were more likely to be HPV positive (P = 0.015). No significant relationships with outcome were detected with either p53 or HPV in the entire population. A subset analysis of patients with stage IV disease revealed that HPV infection was correlated with overall survival. This is the largest study to date to examine both p53 and HPV in patients with SCC of the head and neck. Our results suggest that HPV may be involved in the development of these cancers in patients without traditional risk factors and that HPV-related cancers are more prevalent in the white race.     

Detection of human papillomavirus gene sequences in laryngeal tumors and premalignant changes by polymerase chain reaction

Human papillomavirus gene sequences have been detected in a number of malignant and benign tumours. Non-oncogenic types 6 and 11 are etiological factors of benign mucosal tumours. Types 16 and 18 can be detected in malignancies most often but their role in the etiopathogenesis of cancers is still unclear. In our study we examined formalin-fixed and paraffin-embedded archive laryngeal tissues containing squamous cell carcinoma, papilloma and precancerous lesions for the presence of human papillomavirus genes. As a control we also examined tissues harbouring laryngeal nodules which represented the normal larynx in our study. After DNA preparation from the paraffin blocks we performed polymerase chain reaction to detect the DNA of human papillomavirus types 6, 11, 16 and 18. In the squamous cell carcinomas, papillomas and precancerous lesions the presence of human papillomavirus gene sequences was significantly higher than in the control group. To verify the integrity of DNA we also amplified a sequence deriving from the cellular beta-globin gene. Based on the 100% positivity for this gene we declare that the combination of our DNA preparation and polymerase chain reaction is a reliable method for detecting DNA sequences from formalin-fixed and paraffin-embedded tissues.     

Carcinoma of the lung in Okinawa, Japan: with special reference to squamous cell carcinoma and squamous metaplasia

In Okinawa, a subtropical island in southern Japan, squamous cell carcinoma (SCC), especially the well-differentiated form, is prevalent, while this form is relatively rare in both the mainland and other countries (e.g. United States of America). More patients with SCC from Okinawa, moreover, were positive for human papillomavirus (HPV) DNA by polymerase chain reaction (PCR) (79%), and harbored HPV types 6, 16 and 18, in combination. On the other hand, less than 30% of the mainland patients were positive for HPV DNA by PCR. Those patients who were positive all harbored only one HPV type. Furthermore, in Okinawa, there were a significant number of cases with adenosquamous carcinoma, and they too were positive for HPV DNA. The SCC and the adenocarcinoma cells adjacent to the SCC component in these cases were also positive for HPV DNA, and such adenocarcinoma cells were enlarged in size with relatively wide cytoplasm. The authors postulate that HPV infects adenocarcinoma cells and changes them to enlarged cells, followed by squamous metaplasia. In this report, HPV DNA was transfected to adenocarcinoma cells (cultured cell lines) and this showed that HPV causes squamous metaplasia. In addition, aberrant expression of p53 was demonstrated in a large number of the SCC cases in Okinawa. The enlarged adenocarcinoma cells adjacent to the SCC components in adenosquamous carcinomas also showed aberrant expression of p53. The recent advances in the studies of anti-oncogenes, p53, etc. and oncogenes are outlined. It is to be noted that the molecular mechanisms of carcinogenesis in the lung have been studied in general, classifying lung tumors into two groups, namely, small cell carcinoma (SCLC) and non-small cell carcinoma (NSCLC). However, because human lung cancer is represented by a wide variety of histologic types, molecular genetic studies according to a more detailed histological subclassification is needed.     

Absence of human papillomavirus DNA in the plume of erbium:YAG laser-treated warts

BACKGROUND: The erbium:YAG laser (Continuum Biomedical, Dublin, Calif.) is a new resurfacing and ablating laser that produces minimal residual thermal damage. Laser safety requires careful attention to the hazards of the laser plume. It is important to know whether viable organisms survive in the vapors. Human papillomavirus (HPV) DNA has been detected in the vapor of carbon dioxide laser-treated and electrodesiccated human warts. The presence or absence of HPV DNA in the laser plume of erbium:YAG laser-treated warts has not been previously studied to our knowledge. OBJECTIVE: Our purpose was to determine the presence or absence of HPV DNA in the laser plume of erbium:YAG laser-treated human warts. METHODS: One half of clinically typical and histopathologically confirmed verrucae vulgares from five patients were submitted for HPV DNA detection with in situ hybridization. After erbium:YAG laser ablation of the remainder of the warts, the laser plume was deposited on the handpiece as an abundant fluffy material and was submitted for evaluation of HPV DNA by polymerase chain reaction with consensus primers for the HPV type detected in the wart specimens. RESULTS: HPV2 DNA was found in all warts. HPV DNA was not detected in the erbium:YAG laser plume after ablation of these same warts. CONCLUSION: The absence of HPV DNA in the plume of erbium:YAG laser-treated warts is a significant safety feature of this laser.     

The detection of human papillomavirus in papillomas of the larynx and tonsils through immunohistochemistry and DNA in situ hybridization]

Presenting a study about Human Papillomavirus (HPV) determination by immunohistochemistry and "in situ" hybridization, in 25 samples of squamous cell papillomata (15 tonsilar and 10 laryngeal lesions). Five cases resulted positive for HPV: 2 of them for immunohistochemical probes, other 2 for "in situ" hybridization and only 1 cas showed its positivity for both techniques. All these samples belonging to laryngeal cases. No significant differences were found in antecedents, clinical and histological features related with results obtained. Two patients developed a laryngeal carcinoma after papilloma and they had positive "in situ" hybridization. Literature about diagnosis of HPV-infection was revised.     

Detection of human papillomavirus DNA in nongenital seborrhoeic keratoses

The histological similarities of seborrhoeic keratoses and common warts led to the investigation of the possible occurrence of human papillomavirus DNA (HPV-DNA) in a large number of nongenital seborrhoeic keratoses using the in situ hybridization technique. All specimens derived from normal skin (n = 173) were negative for the applied HPV-DNA probe, whereas the HPV genome was detected in 34 of 173 seborrhoeic keratosis specimens (19.65%). Of 34 HPV-positive specimens, 15 contained types 6/11 and 14 types 31/33/35, and 5 showed no positive reaction to the applied types. These results suggest that a considerable percentage of nongenital seborrhoeic keratoses may be related to an HPV infection.     

Risk factors for HPV detection in archival Pap smears. A population-based study from Greenland and Denmark

The most important risk factor for cervical cancer is genital infection with certain types of human papillomavirus (HPV). The presence of HPV was studied in archival smears from a random sample of women living in Greenland (GW) and Denmark (DW) having, respectively, a high risk and an intermediate risk for cervical cancer. Risk factors were also examined of the original 126 Danish and 129 Greenlandic archived smears collected during October and November 1988. 125 were located from each country including all abnormal smears. HPV DNA was isolated from the smears and detected by means of a consensus polymerase chain reaction (PCR) detecting a broad spectrum of genital HPV types. HPV was detected in all the abnormal smears and in 22 and 33% respectively of the cytological normal smears from DW and GW. Risk of HPV was significantly higher in smears from women who started sexual life relatively recently (respectively, < or = 4 and < or = 6 years ago in DW and GW) compared with > or = 10 years ago (adjusted prevalence-OR: 9.3; 95% CI: 2.2-39.2 in DW and 5.9; 95% CI: 1.4-25.3 in GW). Among other important risk factors were age in both areas, lifetime number of sex partners and current smoking in DW and ever and gonorrhoea in GW. This study confirms the usefulness of the method as all abnormal smears were positive and, furthermore, the predictors for HPV presence in the normal smears corroborate with those found in recent studies of HPV in fresh cervical swabs. Thus, this method can be useful for large-scale epidemiological studies of HPV DNA in already sampled material.     

Gene mutations and increased levels of p53 protein in human squamous cell carcinomas and their cell lines

Using immunocytochemical and Western blotting techniques we have demonstrated the presence of abnormally high levels of p53 protein in 8/24 (33%) of human squamous cell carcinomas (SCC) and 9/18 (50%) of SCC cell lines. There was a correlation between the immunocytochemical results obtained with eight SCC samples and their corresponding cell lines. Direct sequencing of PCR-amplified, reverse transcribed, p53 mRNA confirmed the expression of point mutations in six of the positive cell lines and detected in-frame deletions in two others. We also detected two stop mutations and three out-of-frame deletions in five lines which did not express elevated levels of p53 protein. Several of the mutations found in SCC of the tongue (3/7) were in a region (codons 144-166) previously identified as being a p53 mutational hot spot in non-small cell lung tumours (Mitsudomi et al., 1992). In 11/13 cases only the mutant alleles were expressed suggesting loss or reduced expression of the wild type alleles in these cases. Six of the mutations were also detected in the SCCs from which the lines were derived, strongly suggesting that the mutations occurred, and were selected, in vivo. The 12th mutation GTG-->GGG (valine-->glycine) at codon 216 was expressed in line SCC-12 clone B along with an apparently normal p53 allele and is to our knowledge a novel mutation. Line BICR-19 also expressed a normal p53 allele in addition to one where exon 10 was deleted. Additionally 15 of the SCC lines (including all of those which did not show elevated p53 protein levels) were screened for the presence of human papillomavirus types 16 and 18 and were found to be negative. These results are discussed in relation to the pathogenesis of SCC and the immortalisation of human keratinocytes in vitro.