To the Editor: Esophageal cancer is the sixth most common cancer globally according to the World Health Organization. Due to rapid clinical progression and extremely poor prognosis, the 5-year survival rate of esophageal squamous cell carcinomas (ESCC) remains less than 20%; therefore, further developments in this field are needed. Human papillomavirus (HPV) is a small circular non-enveloped double-stranded DNA virus that primarily infects mucosa and cutaneous keratinocytes and its infection rates in ESCC range from 11.7% to 38.9% worldwide. P16 which is encoded by the CDKN2A gene and known as cyclin-dependent kinase inhibitor 2A, is a widely used immunohistochemical marker in squamous cell carcinomas and associated with high-risk HPV.
The present study included 228 cases from Henan Cancer Hospital, immunostaining for p53 and retinoblastoma protein (Rb) were previously performed for 147 samples, and then 73 ESCC cases were randomly selected for detecting HPV infection and p16 expression. A total of 20 cases were selected through healthy gastroscopy physical examination. This study was approved by the Institutional Ethics Committee of Henan Cancer Hospital (No. 201401017). Sections were incubated with HPV (ZM-0217, CAMVIR-1), p16 (ZM-0205, 1C1), p53 (ZM-0405, BP53.12), or Rb (ZM-0223, 13A10) antibodies from Beijing Zhongshan Jinqiao Biotechnology Co. Ltd, China as the primary antibodies and biotinylated goat anti-rabbit IgG as the secondary antibody. The RNA of HPV 16/18 was detected by the RNAscope 2.5 Assay Reagent Kit (Advanced Cell Diagnostics, Inc., Hayward, CA, USA). All statistical analysis were performed using SPSS 19.0 (SPSS Inc., Chicago, IL, USA). Fisher exact test was used to identify predictors for HPV-positive tumors. The analysis of the 5-year survival rate between different groups was performed using the Kaplan-Meier method and log-rank test. Differences with a value of P < 0.05 were considered statistically significant. All statistical tests were two-sided.
The characteristics of 73 ESCC patients were analyzed and revealed that there were no significant differences between the groups with respect to age (P = 0.708), stage (P = 0.788), T category (P = 0.417), N category (P = 0.788), differentiation grade (P = 0.141), smoking (P = 0.445), and alcohol consumption (P = 0.940). The positive cases of HPV, p53, p16, and Rb were 33 (45.2%), 40 (54.8%), 5 (6.8%), and 32 (43.8%), respectively. The mRNA expression of HPV 16/18 detected through RNAscope 2.5 Assay was negative. The HPV infection in the esophageal mucosa of 20 normal people was all negative. The cases of co-positive HPV and p16, p53, and Rb were 3 (4.1%), 22 (30.1%), and 12 (16.4%), respectively. Among the 73 ESCC patients (for five cases, survival information could not be confirmed), the total number of deaths was 24, and the 5-year survival was evaluated to compare the prognosis from the different groups. The number of deaths of patients with positive HPV, p16, p53, and Rb were 9, 1, 14, and 12; and the number of deaths of patients with negative HPV, p16, p53, and Rb were 15, 23, 10, and 12, respectively. As shown in Figure 1, there was no significant difference in 5-year survival rate between patients with positive or negative HPV, p16, p53, and Rb (χ2 = 0.664, 0.500, 0.008, and 0.262, P = 0.415, 0.479, 0.929, and 0.609, respectively, all P > 0.05).
It is well-known that the p53 and p16 tumor suppressor genes are closely related to the cell cycle. Mutations in the p53 and p16 genes can disrupt the cell cycle regulatory mechanism and induce cell hyperplasia and tumors growth. The rate of HPV infection in 73 ESCC patients was 45.3%; however, statistical analysis showed that the HPV, p16, p53, and Rb were not correlated with the 5-year survival rate of ESCC (all P > 0.05). HPV infection may be related to the occurrence of ESCC, but it is not related to the 5-year survival rate of ESCC patients. The relationship between HPV and ESCC should to be further explored based on a large sample size.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
This work was supported by grants from the Henan Medical Science and Technology Project (general) (No. 201401017) and the National Natural Science Foundation of China (No. 81602637).
Conflicts of interest
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