Methods Drug transporter mRNA expression was quantified from colorectal biopsies and cell-lines by quantitative real-time PCR. Relative mRNA expression was quantified in Caco-2 cells after induction with ARVs. Data was analysed using Pearson’s correlation coefficients (r), hierarchical clustering and principal component analysis (PCA).
Results Expression of 58 of the 84 transporters was documented in colorectal biopsies, with CNT2, P-gp and MRP3 being the highest expressed. No difference was noted between individual subjects, when analysed by age, gender or biopsy site (rectum or recto-sigmoid) (r=0.95-0.99). High expression of P-gp and CNT2 proteins was confirmed by immunohistochemical staining. Similarity between colorectal tissue and cell-line drug transporter gene expression was variable (r = 0.64-0.84). PCA showed distinct clustering of human colorectal biopsy samples with the Caco-2 cells defined as the best surrogate system. Induction of Caco-2 cell-lines with ARV drugs suggests that darunavir-based microbicides incorporating tenofovir may result in drug-drug interactions likely to affect distribution of individual drugs to sub-epithelial target cells.
Conclusions These findings will help optimise complex formulations of rectal microbicides to realise their full potential as an effective approach for pre-exposure prophylaxis against HIV-1 infection.