Human papillomavirus in early laryngeal carcinoma.

OBJECTIVES/HYPOTHESIS: To examine the role of HPV status in the etiology, prognosis, and treatment of head and neck squamous cell carcinoma in early larynx malignancies. STUDY DESIGN: Retrospective. METHODS: Thirty-eight cases of T1 or carcinoma in situ (CIS) laryngeal lesions were examined for the presence of human papilloma virus (HPV) using an inclusive polymerase chain reaction (PCR)/hybridization technique capable of identifying 37 HPV subtypes. RESULTS: HPV DNA was detected in 6 (16%) of the 38 lesions, representing HPV types 16, 26, 31, 39, and 52, and p16 tumor suppressor protein expression was confirmed in 10 representative cases. This HPV prevalence is higher than that noted in many previous laryngeal cancer studies, possibly due to the relatively large panel of subtypes screened for in this study. Identification of HPV-26, which has been associated with uterine cervical cancer, in an early laryngeal cancer specimen represents the first evidence of this subtype in a laryngeal carcinoma. Consistent with reports focusing on head and neck squamous cell carcinoma (HNSCC) arising from other subsites within the upper aerodigestive tract, patients with HPV-positive laryngeal carcinomas were of younger age and were somewhat less likely to have a history of tobacco use, although the latter of the two findings did not reach statistical significance. CONCLUSIONS: Our findings emphasize the presence of a broad spectrum of HPV types in a relevant proportion of early laryngeal cancers, and together with evidence of an association of HPV tumor status with a more favorable clinical course, provide a rationale for the routine HPV testing of small larynx lesions.

Mutagenic effect of cadmium on tetranucleotide repeats in human cells.

Cadmium is a human carcinogen that affects cell proliferation, apoptosis and DNA repair processes that are all important to carcinogenesis. We previously demonstrated that cadmium inhibits DNA mismatch repair (MMR) in yeast cells and in human cell-free extracts (H.W. Jin, A.B. Clark, R.J.C. Slebos, H. Al-Refai, J.A. Taylor, T.A. Kunkel, M.A. Resnick, D.A. Gordenin, Cadmium is a mutagen that acts by inhibiting mismatch repair, Nat. Genet. 34 (3) (2003) 326-329), but cadmium also inhibits DNA excision repair. For this study, we selected a panel of three hypermutable tetranucleotide markers (MycL1, D7S1482 and DXS981) and studied their suitability as readout for the mutagenic effects of cadmium. We used a clonal derivative of the human fibrosarcoma cell line HT1080 to assess mutation levels in microsatellites after cadmium and/or N-methyl-N-nitro-N-nitrosoguanidine (MNNG) exposure to study effects of cadmium in the presence or absence of base damage. Mutations were measured in clonally expanded cells obtained by limiting dilution after exposure to zero dose, 0.5 microM cadmium, 5 nM MNNG or a combination of 0.5 microM cadmium and 5 nM MNNG. Exposure of HT1080-C1 to cadmium led to statistically significant increases in microsatellite mutations, either with or without concurrent exposure to MNNG. A majority of the observed mutant molecules involved 4-nucleotide shifts consistent with DNA slippage mutations that are normally repaired by MMR. These results provide evidence for the mutagenic effects of low, environmentally relevant levels of cadmium in intact human cells and suggest that inhibition of DNA repair is involved.

Gene expression differences associated with human papillomavirus status in head and neck squamous cell carcinoma.

Human papillomavirus (HPV) is associated with a subset of head and neck squamous cell carcinoma (HNSCC). Between 15% and 35% of HNSCCs harbor HPV DNA. Demographic and exposure differences between HPV-positive (HPV+) and negative (HPV-) HNSCCs suggest that HPV+ tumors may constitute a subclass with different biology, whereas clinical differences have also been observed. Gene expression profiles of HPV+ and HPV- tumors were compared with further exploration of the biological effect of HPV in HNSCC. Thirty-six HNSCC tumors were analyzed using Affymetrix Human 133U Plus 2.0 GeneChip and for HPV by PCR and real-time PCR. Eight of 36 (22%) tumors were positive for HPV subtype 16. Statistical analysis using Significance Analysis of Microarrays based on HPV status as a supervising variable resulted in a list of 91 genes that were differentially expressed with statistical significance. Results for a subset of these genes were verified by real-time PCR. Genes highly expressed in HPV+ samples included cell cycle regulators (p16(INK4A), p18, and CDC7) and transcription factors (TAF7L, RFC4, RPA2, and TFDP2). The microarray data were also investigated by mapping genes by chromosomal location (DIGMAP). A large number of genes on chromosome 3q24-qter had high levels of expression in HPV+ tumors. Further investigation of differentially expressed genes may reveal the unique pathways in HPV+ tumors that may explain the different natural history and biological properties of these tumors. These properties may be exploited as a target of novel therapeutic agents in HNSCC treatment.