Epidemiological and mechanistic evidence on the causative role of human
papillomaviruses (HPV) in esophageal squamous cell carcinoma (ESCC) is unclear.
We retrieved alcohol- and formalin-fixed paraffin-embedded ESCC tissues from 133
patients seropositive for antibodies against HPV early proteins, from
high-incidence ESCC regions; South Africa, China, and Iran. With rigorous care
to prevent nucleic acid contamination, we analyzed these tissues for the
presence of 51 mucosotropic human alpha-papillomaviruses by two sensitive,
broad-spectrum genotyping methods, and for the markers of HPV-transformed
phenotype: (i) HPV16/18 viral loads by quantitative real-time PCR, (ii)
type-specific viral mRNA by E6*I/E6 full-length RT-PCR assays and (iii)
expression of cellular protein p16INK4a. Of 118 analyzable ESCC
tissues, 10 (8%) were positive for DNA of HPV types: 16 (four tumors);
33, 35, 45 (one tumor each); 11 (two tumors); and 16, 70 double infection (one
tumor). Inconsistent HPV DNA+ findings by two genotyping methods and negativity
in qPCR indicated very low viral loads. A single HPV16 DNA+ tumor additionally
harbored HPV16 E6*I mRNA but was p16INK4a negative (HPV16 E1
seropositive patient). Another HPV16 DNA+ tumor from an HPV16 E6 seropositive
patient showed p16INK4a up-regulation but no HPV16 mRNA. In the tumor
tissues of these serologically preselected ESCC patients, we did not find
consistent presence of HPV DNA, HPV mRNA or p16INK4a up-regulation.
These results were supported by a meta-analysis of 14 other similar studies
regarding HPV-transformation of ESCC. Our study does not support the etiological
role of the 51 analyzed mucosotropic HPV types in the ESCC carcinogenesis.