CBD and THC Reduced Drug Resistance in Cancer Cells by Decreasing P-Glycoprotein Expression
Prolonged exposure (72 hours) to THC and CBD decreased P-glycoprotein expression in drug-resistant leukemia cells, increasing their sensitivity to the anti-cancer drug vinblastine, while short exposure had no effect.
Quick Facts
What This Study Found
Researchers tested whether cannabinoids affect P-glycoprotein (P-gp), a transporter that pumps anti-cancer drugs out of cancer cells and is a major cause of multidrug resistance.
Short-term (1-hour) exposure to cannabinol, CBD, THC, and a synthetic cannabinoid did not inhibit P-gp drug efflux in either human leukemia cells or mouse cells with the MDR1 gene. This was different from the known P-gp inhibitor PSC833, which did block efflux.
However, prolonged (72-hour) exposure to THC and CBD decreased P-gp protein expression in leukemia cells, similar to the flavonoid curcumin. This reduction in P-gp correlated with increased intracellular drug accumulation and enhanced sensitivity to vinblastine, an anti-cancer drug normally pumped out by P-gp.
Key Numbers
Short exposure (1h): no P-gp inhibition by any cannabinoid. Prolonged exposure (72h): THC and CBD decreased P-gp expression comparable to curcumin. Result: increased intracellular drug accumulation and enhanced vinblastine sensitivity.
How They Did This
In vitro cell study using a drug-resistant human leukemia cell line (CEM/VLB100) and MDR1-transfected mouse fibroblasts. Short-term (1 hour) and prolonged (72 hour) cannabinoid exposures. P-gp function measured by Rhodamine 123 efflux. P-gp expression, drug accumulation, and vinblastine sensitivity assessed.
Why This Research Matters
Multidrug resistance is a major obstacle in cancer chemotherapy. If cannabinoids can reduce expression of the drug resistance transporter P-gp, they might enhance the effectiveness of conventional chemotherapy drugs when used in combination. This is a fundamentally different mechanism from any direct anti-cancer effect.
The Bigger Picture
This finding opens the possibility that cannabinoids could serve as chemotherapy sensitizers rather than direct anti-cancer agents. The time-dependent effect (72 hours needed, not 1 hour) suggests the mechanism involves changes in gene expression rather than direct transport inhibition.
What This Study Doesn't Tell Us
In vitro cell line study. The concentrations and exposure times may not be achievable in patients. Only one drug-resistant cell line was tested in detail. The interaction between cannabinoids and chemotherapy drugs in vivo could be more complex than this simplified model suggests.
Questions This Raises
- ?Do cannabinoids reduce P-gp expression in tumor cells in vivo?
- ?Could combining cannabinoids with standard chemotherapy improve cancer treatment outcomes?
- ?What cannabinoid concentrations are needed at the tumor site?
Trust & Context
- Key Stat:
- 72-hour THC and CBD exposure decreased drug resistance protein P-gp and enhanced vinblastine sensitivity
- Evidence Grade:
- In vitro cell study providing preliminary mechanistic evidence. Important finding but requires extensive further research before clinical application.
- Study Age:
- Published in 2006. Research on cannabinoid-chemotherapy interactions has continued, but clinical evidence for this combination approach remains limited.
- Original Title:
- The effects of cannabinoids on P-glycoprotein transport and expression in multidrug resistant cells.
- Published In:
- Biochemical pharmacology, 71(8), 1146-54 (2006)
- Authors:
- Holland, M L, Panetta, J A, Hoskins, J M, Bebawy, M, Roufogalis, B D, Allen, J D, Arnold, J C
- Database ID:
- RTHC-00230
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
Can cannabinoids make chemotherapy more effective?
This cell study found that prolonged exposure to THC and CBD reduced expression of a drug-resistance protein in leukemia cells, making them more sensitive to the chemotherapy drug vinblastine. However, this is a laboratory finding and has not been confirmed in patients.
Do cannabinoids interfere with cancer treatment?
In this study, cannabinoids did not worsen drug resistance and actually reduced it over 72 hours. However, the interaction between cannabinoids and cancer drugs in actual patients is complex and not yet well-characterized.
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Cite This Study
https://rethinkthc.com/research/RTHC-00230APA
Holland, M L; Panetta, J A; Hoskins, J M; Bebawy, M; Roufogalis, B D; Allen, J D; Arnold, J C. (2006). The effects of cannabinoids on P-glycoprotein transport and expression in multidrug resistant cells.. Biochemical pharmacology, 71(8), 1146-54.
MLA
Holland, M L, et al. "The effects of cannabinoids on P-glycoprotein transport and expression in multidrug resistant cells.." Biochemical pharmacology, 2006.
RethinkTHC
RethinkTHC Research Database. "The effects of cannabinoids on P-glycoprotein transport and ..." RTHC-00230. Retrieved from https://rethinkthc.com/research/holland-2006-the-effects-of-cannabinoids
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.