Detecting Human Papillomavirus 6 & 11 in a Set of Pakistani Population

Introduction: Human papillomavirus 6 &11, two clinically important low risk-HPV genotypes are known for genital warts, laryngeal papillomas and low-risk squamous intraepithelial lesions. Recent research has documented HPV 6 &11, cause of malignancies in oral cavity, pharynx, larynx etc. the frequency of which is also increasing in Pakistan. Therefore, it was hypothesized that HPV 6 & 11 might also be associated with oral malignancies in Pakistan.

Methodology: For this case control study a total of 266 subjects (133 cases and 133 controls), >18yrs, smokers and chewers were recruited. Diagnosed cases of Squamous Cell Carcinoma of the oral cavity, larynx and pharynx were included. Precancerous oral lesions were identified on the basis of Axell & Poulson criteria. According to their classification, subjects falling in grade 1 or above were considered as oral lesion cases. The subjects without any signs similar to grade 1 and without any lesions were controls. Detailed questionnaire was filled followed by oral sample collection. After DNA extraction conventional PCR for HPV was performed. Positive samples were further analyzed for HPV 6 &11 on Real time PCR.

Results: The 266 subjects (mean age cases-42.07±13.7; controls- 33.61±11.68 years) included 132 males [93 (69.9%) cases, 39 (29.3%) controls] and 134 females [40 (30.1%) cases, 94 (70.7%) controls]. Further division into six ethnic groups showed Urdu speaking as major group (40.6% cases and 38.3% controls). Main habit reported was Gutka (67; 25.18%). The most common (68; 95.77%) cancer was Squamous Cell Carcinoma with buccal mucosa (49; 69.01%) as the most common site. HPV was found in 21 (7.9%) cases only. Strong association of HPV with cases (P= 0.006) was found at confidence interval of 3.06-851.8 and odds ratio of 51.02. However none was positive for HPV 6&11. The HPV association was significant with betel quid addiction (P<0.0001). The most common (68; 95.77%) cancer observed was Squamous Cell Carcinoma of the oral cavity with buccal mucosa (49; 69.01%) as the most common site.

Conclusion: Since, HPV 6/11 was not detected we can conclude that there is no association between HPV 6/11 and tobacco use leading to oral lesions/cancers. Thus there is no definitive causative role of HPV 6&11 in oral carcinogenesis in our ethnically diversified population where use of chewable tobacco is very common among the masses.