TLRs constitute important component of innate immune mechanisms1. HPV has been demonstrated to modulate TLR expression and signaling, leading to persistent viral infection and carcinogenesis2. This study was an attempt to understand the gene expression profile of TLRs, their downstream signaling molecules and other cancer initiating pathways triggered by them.
We performed HPV genotyping of the carcinoma and normal cervix using commercially available kits. Cases positive for HPV-16 were proceeded for expression profiling using PCR Array platform of TLRs (TLR 1-9), downstream TLR interacting molecules (MYD88, TICAM1, TICAM2, IRAK 4, IRF3, IRF7), molecules from cancer allied pathways namely AKT, NFĸβ, MDM2, MTOR, p53, CDKN2A in HPV-16 infected, non-infected and carcinoma cervix. The protein expression of the relevant genes was studied at translational level using western blot.
High risk HPV was detected in 23.1% (19/82) of normal cervical tissue. HPV16 (57.8%) was the preponderant subtype detected. 38/57 (66.6%) cases of SCC were HPV 16 positive. An overall down regulation in expression of all TLRs in carcinoma cases was observed with significant difference in TLR-4, TLR-6 and TLR-7 (p value 0.004, 0.050, 0.000). However, we observed highly significant upregulation of CDKN2A, AKT1 (p value 0.000, 0.038) in carcinoma tissue. At protein level, the expression of TLR7, TLR3 was found to be decreased with increase in expression of AKT, MDM2, CDKN2A confirming findings of gene expression.
The study demonstrates that HPV-16 plausibly targets innate immunity by significantly down regulating the expression of TLR-4, 6 and 7 in cervical cancer. In addition the altered expression of PI3K/AKT/MTOR axis and down regulation of p53 suggests involvement of viral oncogenes which are known to increase genomic instability, cellular proliferation and accumulation of mutagenic events resulting in cancer progression. Such events may probably be enhanced by increased expression of MDM2 already identified to act as major negative regulator of tumor suppressor protein p53. Better understanding of the mechanisms employed by HPV for establishing persistence and carcinogenesis may assist in developing specific strategies for treating HPV related cancers.
1. [Akira S, Takeda K. Toll-like receptor signalling. Nat Rev Immunol. 2004; 4: 499-11.]
2. [Q. Zhou, K. Zhu, H. Cheng, Toll-like receptors in human papillomavirus infection. Arch. Immunol. Ther. Exp. (Warsz) 2013; 61: 203–15.]