Re: Human Papillomavirus DNA and p53 Polymorphisms in Squamous Cell Carcinomas From Fanconi Anemia Patients

Kutler et al. (1) recently reported that human papillomavirus (HPV) DNA is frequently detected in squamous cell carcinomas (SCCs) of Fanconi anemia patients, who are predisposed to develop cancer at an early age, particularly acute myeloid leukemia and SCCs of the head and neck (HNSCCs) and the anogenital region. Kutler et al. speculated that HPV infection might be critically involved in the pathogenesis of SCC in Fanconi anemia patients, which raises hope that vaccination against HPV might prevent such tumors. HPV is known to be etiologically involved in SCCs that arise in the anogenital region (cervix) and in a minority of HNSCCs, particularly those in the oropharynx (2,3). Inhibitory oncoproteins expressed by HPV cause inactivation of the p53 and pRb pathways. HNSCCs that contain transcriptionally active HPV DNA typically lack mutations in TP53, the gene encoding p53, whereas 50%–60% of HNSCCs that do not contain HPV DNA have mutations in TP53 (2). Kutler et al. (1) report that 15 of the 18 HNSCCs (all in the oral cavity) from the Fanconi anemia patients in their study had detectable HPV DNA and that none of the 18 HNSCCs contained a mutation in TP53. HPV DNA was detected by polymerase chain reaction (PCR) in laser-microdissected tissue, and quantitative PCR was used to determine the HPV DNA copy number per tumor cell. A cutoff value set at more than one copy per 10 cells was used to designate a sample positive for HPV DNA. We have collected similar information on HNSCCs from Fanconi anemia patients and have obtained different results. Of the five HNSCCs studied, none were HPV DNA-positive and four had a mutation in TP53. Although we studied fewer tumors than Kutler et al., the frequencies of HPV DNA positivity and TP53 mutations are statistically significantly different when comparing their results with ours (P .002 for presence of HPV DNA, and P .001 for mutations in TP53). The basis for these differences is unclear. They may reflect differences in ethnic backgrounds or life-style factors (i.e., tobacco and/or alcohol use, disease history, or sexual behavior) between the patients we studied and those studied by Kutler et al. In addition to patient-related differences, slight differences in HPV DNA detection methodologies might account for part of the discrepancy between our results and those of Kutler et al. We used a semiquantitative PCR-based method with consensus primers and an oligoprobe cocktail to detect the DNA of 14 high-risk HPV types in total tumor DNA; this method can detect as few as one copy of HPV16 DNA per 5000 cells (4). However, none of the HNSCC specimens from the Fanconi anemia patients we tested were positive for HPV DNA, which made further quantitative analysis redundant. Results of previous studies suggest that the likely involvement of HPV in the etiology of a tumor is reflected by the presence of at least one copy of HPV DNA in every cancer cell (2,5). To obtain independent confirmation of the HPV DNA status of HNSCCs from Fanconi anemia patients, we suggest that loss-of-heterozygosity patterns in the tumor DNA could be evaluated, because we have found that HNSCCs with transcriptionally active HPV DNA appear to exhibit a loss-of-heterozygosity pattern that is strikingly different from that observed among HNSCCs without detectable HPV DNA (6). Until these issues have been examined in more detail, we wish to caution against raising too much hope that HPV vaccination (7) will be an option to prevent HNSCC in Fanconi anemia patients. The current policy of frequent surveillance and examination of biopsy samples of suspected tissues in the oral cavity and oropharynx should remain part of the standard practice in the clinical management of Fanconi anemia patients, including those who are enrolled in preventive vaccination trials.