Background: We have previously found that the PC-PLC inhibitor LMV-601 inhibits transcription of episomal HPV-31 genomes in premalignant transformed human keratinocytes (CIN 612 9E HPV-31 infected cervical epithelial cells). Concomitantly, HPV DNA replication stopped and with prolonged treatment cells were cured from HPV, lost their transformed phenotype and finally became senescent [Amtmann E. et al., Int J of Infect Dis, 2010 March, 14 (Suppl.1): e465]. In this study we wanted to investigate whether LMV-601 is also active on other HPV types and on the expression of integrated HPV genomes. LMV-601 is (-)-exo,exo-O-Tricyclo-[18.104.22.168(2,6)]-dec-9-yl-dithiocarbonate potassium salt
Methods: CaSki (containing HPV-16) and HeLa (containing HPV-18) cervical carcinoma cells were treated with LMV-601. (a) After 72 h the effect on level of retinoblastoma (RB) gene ( Western Blot) was analyzed. (b) Over 3 passages growth rate (cell counting), level of E7 mRNA (real time PCR) and expression of senescence marker beta-galactosidase (x-gal staining) were determined.
Results: (a) Levels of RB gene were up-regulated: EC50 12 µg/mL for CaSki and ca. 20 µg/mL for HeLa cells. (b) In passage 1 IC50 was 30 µg/mL for CaSki and 35 µg/mL for HeLa cells. Growth inhibition was cumulative. In passage 3 the factor of multiplication was 50, at concentrations of ≥ 80 µg/mL expression of E7 was reduced by a factor of ca. 1000 in both cell lines. After 3 passages at 40 µg/mL > 50 % of HeLa and CaSki cells were senescent.
Conclusions: 1. The PC-PLC inhibitor LMV-601 is active on at least three different high risk HPV types (16, 18 and 31) found in the majority of cervical cancers. 2. LMV-601 inhibits expression of E7, both in episomal and in integrated HPV genomes. 3. With prolonged treatment , HPV transformed premalignant and malignant cells become senescent.