The absence of human papillomavirus in esophageal squamous cell carcinoma in East China

Abstract

Esophageal squamous cell carcinoma (ESCC) is one of the most common types of tumors worldwide, particularly in China, and human papillomavirus (HPV) is thought to be a potential risk factor for this cancer. To determine whether this is true, we collected 177 formalin-fixed and paraffin-embedded ESCC samples from two hospitals. We screened for 23 different HPV genotypes using a human papillomavirus genotyping kit, which allowed us to amplify the L1 gene by polymerase chain reaction (PCR) and test for 23 HPV subtypes by reverse dot blot (RDB) on a single membrane. We also used immunohistochemistry (IHC) to detect the P16(INK4a) protein, the expression of which is linked to HPV E7 activity and which is used to diagnose cervical intraepithelial neoplasia. The genotyping results showed that only six samples were weakly positive for HPV: two for HPV16, two for HPV11 and two for HPV35, with no samples showing strong positive signals. The IHC results showed only five samples with diffuse positive staining, with the other samples being completely negative or having only focal positive signals, which were considered as negative. This study demonstrates that the HPV infection rate in ESCC samples is very low, suggesting that HPV is not the etiological cause of ESCC.

Keywords: Human papillomavirus; P16INK4a; PCR; RBD; esophageal squamous cell carcinoma.

Figure 1

Images of typical H&E and IHC staining. Images were collected using a light microscope at 100 × magnification. The tissue sections were scored using the following criteria: panel A: Well-differentiated ESCC with squamous pearl formations; panel B: Moderately differentiated ESCC; panel C: Poorly differentiated ESCC with predominantly basal-like cells forming nests with central necrotic regions; panel D: Completely negative P16^INK4a expression; panel E: Negative expression of P16^INK4a with focal staining; and panel F: Positive expression of P16^INK4a with intense staining. Panels A-C were prepared by H&E staining. Panels D-F were prepared by IHC staining.

Figure 2

Images of typical HPV genotyping results. Clear round blue dots on the labeled grid were considered as positive signals for the corresponding HPV subtype; the PC grid shows the internal β-globin positive control. Membrane (A) was only positive for PC and was therefore scored as negative. Membrane (B) showed a clear light blue dot at position 16 on the grid and was therefore considered weakly positive for HPV16. Membrane (C) showed two dots at positions 16 and 43 on the grid and was therefore considered positive for HPV 16 and 43, which was from the HPV multiple infection cervical intraepithelial neoplasia sample. The patients’ information was mosaicked.