Enhancement of paclitaxel production by reduced cellular accumulation and alteration in expression pattern of key genes using multi-walled carbon nanotube in Taxus baccata L. cell suspension culture

Paclitaxel (PTX) is an effective chemotherapeutic agent widely used against variety of cancers. PTX is found in the inner bark of several Taxus species. The small-scale of PTX production in Taxus spp. is improved by the platforms based on cell cultures through elicitation. Due to the accumulation of this metabolite in cells and the negative feedback effects, high PTX production level is unavailable. In this context, the effect of multi-walled carbon nanotube (MWCNT) was studied at 100 and 250 mg/L on PTX secretion, feedback reduction, and ultimately increased production of PTX in T. baccata cell suspension culture. The expression pattern of 10 key genes at the up- and downstream of PTX biosynthesis pathway was also evaluated 4 and 72 h after treatment. Our results revealed that under 100 mg/L MWCNT treatment, 18% of total PTX was secreted into the culture medium, while this strongly increased to 96% in 250 mg/L. Correspondingly, the total PTX production increased by 2.7-fold on the 23rd day at 100 mg/L and elevated to 6.7-fold by 250 mg/L compared to the control (non-treated with MWCNT). The expression pattern of ABC transporter gene confirmed the results and showed 2.3-fold reduction in response to 250 mg/L MWCNT compared to the 100 mg/L. The removal of PTX from the cells at 100 mg/L MWCNT enhanced the expression level of upstream genes including GGPP, TXS, T5 alpha OH, T10BOH, T13 alpha OH, and T14BOH. With more PTX secretion to the culture medium at 250 mg/L MWCNT, more expression level was also detected for the DBAT, BAPT, and DBTNBT genes close to the final product (PTX). Our results clearly demonstrated that reduction of negative feedback from PTX biosynthesis pathway by secretion out of the cell can highly improve PTX production, especially under elicitation treatments.