Cannabidiol suppresses 3-dimensional ovarian cancer growth and may enhance potency of classic and epigenetic therapies

Objectives: High-grade serous ovarian cancer (HGSOC) is the leading cause of death from gynecological cancer in the US. The majority of patients will present at advanced stage and will recur due to chemoresistance. New therapeutic strategies such as epigenetic and cannabinoid-based therapies may help circumvent this chemoresistance problem. We aim to determine the potency of clinically relevant concentrations of CBD monotherapy as well as combined with epigenetic (ET) and classic chemotherapy on tumor formation and propagation in 3-Dimensional (3D) ovarian cancer (OC) spheroid models. Methods: We created our clinically relevant 3D spheroid tissue culture model in order to mimic physiological conditions in vivo with platinum sensitive OC cell lines. Spheroids were treated with both one time and chronic doses of cannabidiol (CBD) at pre-determined concentrations alone or in combination with chemotherapeutic and epigenetic drugs (Cisplatin/Paclitaxel, Panobinostat). Spheroid growth and morphology were evaluated over an extended time kinetic (days 0, 3, 6, 10/12) and measured by volume of growth. The average radius of the spheroids was used to calculate the spheroid volume according the formula V = 4/3 πr3 and was monitored for percent growth relative to spheroid size at the beginning of the experiment (day 0). Microscopic pictures were taken to follow the morphologic changes. Results: Over an extended kinetic, high and medium concentrations of one time CBD (CBDH) tended to stunt spheroid growth in comparison to control, (686% and over 700% less growth). Low concentrations of one time CBD (CBDL) had a lessened effect on spheroid growth, (556% less growth). Classic chemotherapy combined with CBD contributed to a decreased overall spheroid growth, and even shrinkage with one time CBDL (34% shrinkage versus 84% growth in C/T group) over an extended kinetic. Chronic CBDH administration resulted in greater than 7500% less growth by day 10. Chronic CBDL in combination with C/T resulted in a 99% less growth in comparison to C/T by day 6. One time CBD administration with Panobinostat (Pano) decreased the amount of growth over a shorter kinetic (18% and 2% shrinkage for Pano/CBDL and Pano/CBDM, respectively, versus 13% growth for Pano). With the application of chronic CBD, Pano and CBD resulted in shrinkage early on and even 100% lysis of 3D OC by day 10. Conclusions: As demonstrated by our results, clinically relevant concentrations of CBD possess antitumorigenic effects on OC cells. Further, our data using the combination of Panobinostat with varying concentrations of CBD leads us to hypothesize that a one-time dose of CBD is not sufficient for prolonged antitumorigenic effects, with a synergistic effect demonstrated by chronic administration of CBD. Regarding classic chemotherapy and the effect of varying concentrations of CBD, our data indicates a synergistic effect exists with low concentrations of CBD. Further studies are indicated to determine whether these synergistic effects can aid in the reversal of chemoresistance and enhance the efficacy of targeted treatments. High-grade serous ovarian cancer (HGSOC) is the leading cause of death from gynecological cancer in the US. The majority of patients will present at advanced stage and will recur due to chemoresistance. New therapeutic strategies such as epigenetic and cannabinoid-based therapies may help circumvent this chemoresistance problem. We aim to determine the potency of clinically relevant concentrations of CBD monotherapy as well as combined with epigenetic (ET) and classic chemotherapy on tumor formation and propagation in 3-Dimensional (3D) ovarian cancer (OC) spheroid models. We created our clinically relevant 3D spheroid tissue culture model in order to mimic physiological conditions in vivo with platinum sensitive OC cell lines. Spheroids were treated with both one time and chronic doses of cannabidiol (CBD) at pre-determined concentrations alone or in combination with chemotherapeutic and epigenetic drugs (Cisplatin/Paclitaxel, Panobinostat). Spheroid growth and morphology were evaluated over an extended time kinetic (days 0, 3, 6, 10/12) and measured by volume of growth. The average radius of the spheroids was used to calculate the spheroid volume according the formula V = 4/3 πr3 and was monitored for percent growth relative to spheroid size at the beginning of the experiment (day 0). Microscopic pictures were taken to follow the morphologic changes. Over an extended kinetic, high and medium concentrations of one time CBD (CBDH) tended to stunt spheroid growth in comparison to control, (686% and over 700% less growth). Low concentrations of one time CBD (CBDL) had a lessened effect on spheroid growth, (556% less growth). Classic chemotherapy combined with CBD contributed to a decreased overall spheroid growth, and even shrinkage with one time CBDL (34% shrinkage versus 84% growth in C/T group) over an extended kinetic. Chronic CBDH administration resulted in greater than 7500% less growth by day 10. Chronic CBDL in combination with C/T resulted in a 99% less growth in comparison to C/T by day 6. One time CBD administration with Panobinostat (Pano) decreased the amount of growth over a shorter kinetic (18% and 2% shrinkage for Pano/CBDL and Pano/CBDM, respectively, versus 13% growth for Pano). With the application of chronic CBD, Pano and CBD resulted in shrinkage early on and even 100% lysis of 3D OC by day 10. As demonstrated by our results, clinically relevant concentrations of CBD possess antitumorigenic effects on OC cells. Further, our data using the combination of Panobinostat with varying concentrations of CBD leads us to hypothesize that a one-time dose of CBD is not sufficient for prolonged antitumorigenic effects, with a synergistic effect demonstrated by chronic administration of CBD. Regarding classic chemotherapy and the effect of varying concentrations of CBD, our data indicates a synergistic effect exists with low concentrations of CBD. Further studies are indicated to determine whether these synergistic effects can aid in the reversal of chemoresistance and enhance the efficacy of targeted treatments.