THC-rich marijuana extracts triggered programmed cell death in leukemia cells while activating biological signals associated with immune recognition of cancer, according to new laboratory research accepted for publication in Frontiers in Immunology.
The study, conducted by researchers affiliated with the Juan N. Corpas University Foundation in Bogotá, Colombia, examined how marijuana extracts with different THC and CBD concentrations affected two human leukemia cell lines and the activity of immune cells known as macrophages.
Researchers, led by Sandra Paola Santander Gonzalez, prepared extracts from six marijuana varieties and classified them into two groups: THC-dominant extracts with high THC-to-CBD ratios and CBD-dominant extracts with high CBD-to-THC ratios.
Both categories induced biological changes associated with programmed cell death, known as apoptosis. However, THC-rich extracts demonstrated stronger cancer-cell-killing activity and produced a more coordinated release of molecular signals associated with immunogenic cell death, a process in which dying cancer cells generate signals that can alert the immune system.
Researchers identified several important responses, including increased oxidative stress, exposure of the protein calreticulin on cell surfaces and the release of ATP and HMGB1. These molecules can help immune cells recognize damaged or dying cells and are considered important indicators of immunogenic cell death.
CBD-dominant extracts also produced cellular effects, but they did not trigger the same coordinated release of immune-related signals.
The researchers then examined how macrophages responded to leukemia cells treated with THC-rich extracts. The results differed depending on the leukemia cell line involved.
Macrophages exposed to treated U937 leukemia cells developed characteristics associated with inflammation and antigen presentation, processes involved in activating immune defenses. In contrast, macrophages exposed to treated K562 leukemia cells demonstrated a more regulatory-like response.
The findings suggest that marijuana extracts may affect not only cancer-cell survival but also the interaction between dying cancer cells and the immune system. However, the differing macrophage responses indicate that these effects depend partly on the biological characteristics of the cancer cells themselves.
The study was conducted using laboratory cell cultures rather than patients or animal models, with researchers examining cellular responses over periods of up to 72 hours.
Accepted October 16, the research provides additional evidence that the cannabinoid composition of marijuana extracts can substantially influence their biological activity, particularly their ability to activate pathways associated with cancer-cell death and immune signaling.
