PROJECT SUMMARY/ABSTRACT
Patients diagnosed with advanced cancers typically required systemic therapies, which include chemotherapy,
targeted therapy, and immunotherapy. This proposal will address major issues affecting clinical outcomes; the
question of which patient will respond to which therapy, and the question of what factors are associated with
intrinsic or acquired resistance. Although intrinsic resistance can sometimes be clearly assigned to tumor-specific
factors, such as specific somatic mutations, in many cases the underlying basis for resistance is obscure. This
proposal will address the novel hypothesis that use of cannabidiol (CBD) provides an under-appreciated source
of variation in response to clinically important cancer therapies. A growing number of individuals use CBD during
cancer treatment to alleviate cancer pain, or even because of perceived benefits for treating their cancers. In the
past, there has been relatively limited study of CBD and other cannabis-derived phytochemicals due to issues
of social stigma and legal restrictions; however, a growing number of studies have generated convincing
evidence that CBD affects the growth of some types of tumors and interacts with cytotoxic chemotherapies to
modulate their activity. Some studies have demonstrated interaction between CBD cellular receptors and
signaling by EGFR, SRC, and other signaling proteins that are important therapeutic targets, implying CBD might
affect response to drugs targeting those proteins. However, no published studies in any cancer type have
systematically probed the interaction of CBD with the signaling pathways commonly targeted in cancer therapy.
In pilot studies, we have been investigating the interaction of CBD with 175 kinase-targeted inhibitors and
additional control compounds in restricting the growth of cancer cells. This has identified several specific CBD-
inhibitor interactions, which differed between two cell models tested, but were more notable in an EGFR-
dependent cell model. Given multiple connections identified between CBD and EGFR signaling detected, the
objective of this proposal is to evaluate the degree to which CBD influences the activity of pathway-targeted
inhibitors in two EGFR-dependent tumor types (head and neck squamous cell carcinoma (HNSCC), and
colorectal cancer (CRC)), and to characterize the underlying mechanisms of CBD-inhibitor interaction. In Aim 1,
we will screen the targeted inhibitor library in additional HNSCC and CRC cell models to establish consistent
patterns of interaction, using CellTiterBlue and nuclear count as initial screening assays. Positive hits will be
further explored using clonogenic and 3D spheroid growth analysis, and dose range of interaction defined.
Reverse-phase protein array (RPPA) analysis will be used to establish signaling pathways specifically affected
by CBD-inhibitor interaction. In Aim 2, for selected specific protein-targeted inhibitors of interest, we will define
the CBD-inhibitor interaction in xenograft and patient-derived xenograft (PDX) models in vivo, confirm CBD-
dependent signaling changes defined in vitro pertain in vivo, and use bioinformatic analysis of large data
resources to understand the relationship between CBD receptor expression, prognosis, and drug response.