Efavirenz Has the Highest Anti-Proliferative Effect of Non-Nucleoside Reverse Transcriptase Inhibitors against Pancreatic Cancer Cells

Background Cancer prevention and therapy in HIV-1-infected patients will play an important role in future. The non-nucleoside reverse transcriptase inhibitors (NNRTI) Efavirenz and Nevirapine are cytotoxic against cancer cells in vitro. As other NNRTIs have not been studied so far, all clinically used NNRTIs were tested and the in vitro toxic concentrations were compared to drug levels in patients to predict possible anti-cancer effects in vivo. Methods Cytotoxicity was studied by Annexin-V-APC/7AAD staining and flow cytometry in the pancreatic cancer cell lines BxPC-3 and Panc-1 and confirmed by colony formation assays. The 50% effective cytotoxic concentrations (EC50) were calculated and compared to the blood levels in our patients and published data. Results The in vitro EC50 of the different drugs in the BxPC-3 pancreatic cancer cells were: Efavirenz 31.5$\mu$mol/l (= 9944ng/ml), Nevirapine 239$\mu$mol/l (= 63786ng/ml), Etravirine 89.0$\mu$mol/l (= 38740ng/ml), Lersivirine 543$\mu$mol/l (= 168523ng/ml), Delavirdine 171$\mu$mol/l (= 78072ng/ml), Rilpivirine 24.4$\mu$mol/l (= 8941ng/ml). As Efavirenz and Rilpivirine had the highest cytotoxic potential and Nevirapine is frequently used in HIV-1 positive patients, the results of these three drugs were further studied in Panc-1 pancreatic cancer cells and confirmed with colony formation assays. 205 patient blood levels of Efavirenz, 127 of Rilpivirine and 31 of Nevirapine were analyzed. The mean blood level of Efavirenz was 3587ng/ml (range 162-15363ng/ml), of Rilpivirine 144ng/ml (range 0-572ng/ml) and of Nevirapine 4955ng/ml (range 1856-8697ng/ml). Blood levels from our patients and from published data had comparable Efavirenz levels to the in vitro toxic EC50 in about 1 to 5% of all patients. Conclusion All studied NNRTIs were toxic against cancer cells. A low percentage of patients taking Efavirenz reached in vitro cytotoxic blood levels. It can be speculated that in HIV-1 positive patients having high Efavirenz blood levels pancreatic cancer incidence might be reduced. Efavirenz might be a new option in the treatment of cancer

Effect of EFV, NVP and RPV on the survival fraction of cancer cells.

<p>Colony formation assays were performed with (a) EFV, (b) NVP and (c) RPV. The pancreatic cancer cell line BxPC-3 was treated for 72h with each of the drugs. The survival fraction (SF) was analyzed and normalized to the control. Graphs were fitted and the EC50 was calculated.</p

Chemical structures of the studied non-nucleoside reverse transcriptase inhibitors.

<p>Chemical structures of the studied non-nucleoside reverse transcriptase inhibitors.</p

Apoptosis and necrosis induction in cancer cells by non-nucleoside reverse transcriptase inhibitors.

<p>The fraction of apoptotic and necrotic cells after treatment with different NNRTIs in different concentrations was measured by Annexin-V-APC/7AAD staining and flow cytometry. An example of the gating in the FACS plots is shown for untreated (a) and with a toxic concentration of EFV treated cells (b). A curve was fitted through the data points of the total fraction of dead cells and the EC50 was calculated for each drug. The pancreatic cancer cell line BxPC-3 was treated for 72h with (c) EFV, (d) NVP, (e) RPV, (f) ETR, (g) LSV and (h) DLV. The pancreatic cancer cell line Panc-1 was treated for 72h with (j) EFV, (k) NVP and (l) RPV.</p

Comparison of blood levels in patients with in vitro toxic EC50 of EFV, NVP and RPV.

<p>Blood levels of (a) EFV, (b) NVP and (c) RPV determined by HPLC (bars). These in vivo concentrations are compared to the fitted function of the in vitro toxicity against BxPC-3 pancreatic cancer cells in the Annexin-V-APC/AAD staining (solid line).</p