Exploring cannabinoids for indolent B-cell lymphomas

Abstract

The overexpression of cannabinoid receptors is well described in several indolent lymphomas but the relevance of this finding is more uncertain. Our group has previously shown that mantle cell lymphoma (MCL)-derived cell lines known to overexpress the cannabinoid receptor 1 entered apoptosis after exposure to cannabinoids and that lymphomas xenografted onto mice shrank in size after exposure to cannabinoids. To further understand the potential effects of cannabinoids on indolent lymphomas, we therefore undertook a clinical trial and subsequent correlational studies which are described in this thesis.

In the trial, we recruited 23 patients with leukemic indolent B-cell lymphomas from our hematologic out-patient clinic. The patients were given cannabinoids in the form of a mouth-spray (Sativex®) with doses escalating between the patients to identify the maximal tolerated dose. The patients were blood sampled at regular intervals, both during a control day and on the day on the cannabinoid study drug administration. After a week, a final sample was taken. This longitudinal sampling allowed us to investigate what, if any, effects the cannabinoids had on the indolent B-cell lymphoma cells. Our analysis told us that the absolute number of circulating lymphocytes decreased after administration of cannabinoids but there was no evidence of apoptosis, neither was there any evidence of decreased proliferation, in the lymphoma cells. Instead, we surmised that a migration of lymphocytes away from the blood stream was the most likely explanation to our findings.

The second study focused on the pharmacological perspectives of the abovedescribed clinical trial. All 23 patients underwent testing of captured breath, saliva, urine and blood during their participation in the study. From this we learned that the newer method of captured breath to detect cannabinoids was very sensitive and gave false positives if not very carefully handled. We also found that the urine analysis was surprisingly sensitive for a long period of time and in some cases cannabinoids were detected a week after administration in patients that received very small doses of the study drug. Both these findings have practical implications, for example when testing is conducted in workplaces and in traffic monitoring.

Our third study investigated the possible interplay between the two types of cannabinoid receptors and how they affect cell migration. We used primary cells from patients and several different MCL-cell lines to discern what type of cannabinoid receptor was important in cell migration. We also investigated how the receptors communicate with each other and interact with the known potent chemokine receptor C-X-C Chemokine Receptor type 4 (CXCR-4).

Paper IV is a manuscript detailing our ongoing work to identify the effects cannabinoids have on lymphoma cells. In this paper we take frozen lymphoma cells from the clinical trial and analyse them using RNA-sequencing (RNA-seq). Since we had cells saved from all the various timepoint of the study, we could produce a longitudinal analysis of how mRNA-levels changed after administration of cannabinoids.