Combination therapy, a treatment modality that studies the effect of two or more drugs is the most common strategy used to overcome drug resistance in cancer. Cannabinoids have been proven to be potential anticancer agents. Terpenes have also been demonstrated to exhibit anticancer activity. The purpose of this study was to evaluate the effect of combinations of various cannabinoids and terpenes against drug resistant lung and breast cancer. Several cannabinoids and terpenes such as cannabidiol (CBD), cannabichromene (CBC), cannabidiolic acid (CBDA), cannabidivarin (CBDV), cannabinol (CBN), cannabigerol (CBG) and βcaryophyllene (BC), bisabolol, myrcene, linalool, limonene, geraniol, neralidol, α-pinene, αterpineol, γ-terpinene respectively were screened for their anticancer activity against MDA MB 231 DOX RT, H1975 OSM RT, PDX Lung cancer cell lines using 2D cytotoxicity and 3D spheroids assay. It was found that the cytotoxic potential of combinations of cannabinoids with BC increased by 10 folds in comparison to their individual anticancer activity. The combinations that exhibit synergistic action were determined from combination index (CI) values using compusyn software. Other assays such as colony formation, wound healing, apoptotic assay, cell cycle analysis by flow cytometry elucidated the possible mechanism underlying the synergism of the combinations investigated. CBC+BC was proven to be the most potent combination from all the in-vitro studies and hence was further evaluated in in-vivo tumor xenografts. Briefly, 5 million MDA MB 231 DOX RT cells were injected by S.C route in the right flank region of BALB/c nude mice. The animals were treated after the tumor volume reached 180-200mm3 . The animals were administered CBC (15mg/kg, i.p.), BC (100mg/kg, i.p.) and CBC+BC thrice a week for two weeks. The tumor volume in the combination group was reduced by 2 folds relative to individual treatments and 4 folds relative to control. Western blot analysis of tumor xenografts showed downregulation of apoptotic markers such as PARP, mTOR, pAMPK, Survivin, autophagy markers such as LC 3, Glypican 5 and migration markers such as vimentin and Integrin. Immune check point proteins such as PD-L1 and PD-1 were also downregulated by combination treatment. This was further validated by qPCR. In conclusion, CBC induces programmed cell death in tumors and induces autophagy whereas BC inhibits migration and thus this combination was able to overcome resistance than individual therapies in a synergistic fashion.

Learning Objectives:

• The audience will get an understanding of the role of Terpenes and Cannabinoids in cancer

• The audience will get a better understanding the mechanisms of action of Terpenes and also CBD in overcoming resistance in Triple negative breast cancer