Phylogenetic analysis of Human papillomavirus 16 variants isolated from Indian Breast cancer patients showed difference in genetic diversity with that of cervical cancer isolates

- A comprehensive portrait of differences in genetic diversity of HPV16 in Indian BC and CACX patients.
- High genetic diversity of both LCR and E6/E7 region was evident in BC than CACX.
- Variants in LCR, E6 and E7 were found unique to both the tumours.
- The D98Y (395 G > T) variant of E6 protein was positively selected in BC, unlike R48W (245 G > T) in CACX.
- Significant clinico-pathological correlation was seen with positively selected variants.

The genetic variations of HPV16 in Breast Cancer (BC) are not well studied unlike HPV16 in Cervical Cancer (CACX). In this study, the genetic variations of HPV16 in BC were compared with HPV16 in CACX. In sequencing analysis of LCR, E6 and E7 regions of HPV16 in BC and CACX the A lineage was seen to be 64.2% and 66.6% respectively. The other lineages showed differential frequency in BC and CACX. The mutation frequency index of the regions in BC and CACX was in the following order: LCR > E6 > E7. However, the inter-patient genetic diversity in LCR and E6/E7 regions was high in BC than CACX. The LCR region showed more variations than the E6/E7 region in BC. Apart from some common variations, some unique tissue specific variants in LCR and E6/E7 region were seen in BC and in CACX. Besides the selection of some common variants in both BC and CACX, some unique variants in BC (D98Y; 395 G > T) and CACX (R48W; 245 G > T) were observed. The 7521 G > A variant of LCR showed association with Luminal B subtype of BC and progression of CACX. Whereas, 145 G > T (Q14H) and 335 C > T (H78Y) variants of E6 showed association with either early invasiveness of BC and/or poor outcome of the patients. Thus, this study indicates that there may be a difference in the genetic variation of HPV16 in BC and in CACX.