There is a version of the cannabis-and-cancer conversation that happens in wellness circles, in dispensaries, and in anxious family group chats, and it is mostly driven by anecdote, hope, and incomplete information. There is a different version happening in peer-reviewed journals, and it is considerably more interesting — and considerably more careful — than either the enthusiastic claims or the dismissive counter-claims that dominate public discourse.

A review published in November 2024 in the International Journal of Molecular Sciences, authored by researcher Bozena Bukowska at the University of Lodz in Poland, compiled and assessed 157 studies on the biologically active compounds of Cannabis sativa and their effects on disease. The section that commands the most data — and the most nuance — covers cancer. What follows is a careful reading of those findings, organised by cancer type and written to reflect both what the evidence shows and what it does not yet prove.

Why Cannabinoids Are Being Studied in Oncology at All

Cancer can alter the endocannabinoid system — the body's own network of receptors and signalling molecules that regulate everything from pain to immune response to cell survival. THC and CBD interact with this system in ways that have measurable effects on cancer cells in the laboratory. Cannabinoids appear to influence several of the fundamental processes that make cancer dangerous: how quickly cancer cells divide, whether they die when they should, whether they spread to new locations, and whether they can recruit new blood vessels to feed tumour growth.

The research in this review draws on three levels of evidence. In vitro studies test compounds on cancer cells in laboratory dishes. In vivo studies test them in living animals, usually mice. Clinical trials test them in human patients. Each level carries different weight, and the distinctions matter enormously. A compound that kills cancer cells in a dish has cleared a very low bar. A compound that shrinks tumours in mice has cleared a higher one. A compound that improves survival in human patients has cleared the bar that actually matters.

Lung Cancer — Multiple Mechanisms, Consistent Direction

The evidence in lung cancer is among the most detailed in the review, with several independent research teams arriving at consistent conclusions through different experimental approaches.

Cannabidiol was shown to decrease the viability of human lung cancer cells by triggering apoptosis — the process by which cells destroy themselves in an orderly, programmed way. The mechanism involved the upregulation of two proteins: COX-2 and PPAR-gamma. When cancer cells treated with cannabidiol were examined, elevated levels of COX-2-dependent prostaglandins were found. These prostaglandins moved PPAR-gamma into the cell nucleus, where it triggered apoptotic cell death. In animal experiments using lung cancer cells implanted in nude mice, the same mechanism appeared to operate in a living organism, and tumour regression was observed — an important step in establishing biological relevance beyond the laboratory dish.

A separate line of investigation looked at cancer invasion — the ability of cancer cells to spread into surrounding tissue, which is one of the features that makes cancer deadly. Cannabidiol, THC, and a stable analogue of the endocannabinoid anandamide all slowed the invasion of human lung carcinoma cells. The mechanism traced back to a protein called TIMP-1, a tissue inhibitor of metalloproteinases, whose elevated expression appeared to mediate the anti-invasive effect. The authors of that study went so far as to recommend cannabinoids in the treatment of highly invasive cancers.

An in vivo study using a Lewis lung cancer grafted mouse model found that Cannabis sativa essential oil significantly inhibited tumour growth, reduced tumour inflammatory markers including TNF-alpha and IL-6, and increased the numbers of immune-related T lymphocytes — suggesting the anti-tumour effect may in part operate through the immune system rather than by acting directly on cancer cells alone.

Liver Cancer — CBD Amplifying an Existing Drug

In hepatocellular carcinoma — the most common form of liver cancer — researchers examined what happened when cannabidiol was combined with cabozantinib, a multi-kinase inhibitor already used in cancer treatment. Cannabidiol increased the death of apoptotic cells caused by cabozantinib through the phosphorylation of p53, a well-known tumour suppressor protein, regulated by endoplasmic reticulum stress in liver cancer cells.

Prostate Cancer — Cell Death Through Multiple Pathways

Research on prostate cancer cells found that a combination of cannabis extract, cannabidiol, and cisplatin caused antiproliferation of PC3 cancer cells by increasing the activity of caspase 3 and caspase 7 — enzymes that execute the apoptotic process inside cells. Silencing a protein called RBBP6 produced apoptotic changes alongside upregulation of TP53 and Bax expression and downregulation of Bcl-2. This combination — more pro-apoptotic signalling, less anti-apoptotic protection — pushes cells toward death. In mouse experiments, tumours decreased in size after treatment with cisplatin and cannabidiol.

A Phase I clinical trial using Epidiolex — the pharmaceutical-grade cannabidiol preparation approved by the FDA — enrolled 18 patients with biochemically recurrent prostate cancer. At 800 milligrams per day, it was well tolerated with an acceptable safety profile. The authors were clear about the limitations: short treatment duration, small sample size, no comparator group. This is early human data, not a clinical recommendation, but it establishes that the compound can be administered to prostate cancer patients without obvious acute safety problems.

Breast Cancer — Blocking Proliferation and Colony Formation

Research on breast cancer cells documented cannabidiol blocking proliferation through reactive oxygen species-mediated endoplasmic reticulum stress. Cannabinol — a cannabinoid that receives comparatively little commercial attention — was found to induce apoptosis in breast cancer cell lines by downregulating p21 and p27, and arresting the cell cycle in the G1 or S phase by reducing CDK1, CDK2, and cyclin E1 levels.

Cannabigerol, commonly known as CBG, was found to reduce the amount of macrophages associated with tumours and deplete colony-stimulating factor 1 secretion from melanoma cells — a mechanism with relevance to breast cancer given that CSF-1 plays a role in tumour microenvironment regulation across multiple cancer types. The review also notes that synergistic effects have been observed for the combination of cannabidiol with cannabichromene or THC, where small concentrations of cannabinoid combinations can replicate the effect of much higher doses of either compound alone.

Melanoma — Tumour Shrinkage in Animals, Apoptosis in Cells

The melanoma evidence is both mechanistically detailed and, in terms of animal data, among the more striking in the review.

A further study found that a mixture of THC and CBD triggered apoptosis in human melanoma cells by upregulating several genes including DNA damage-induced transcript 3 and E2F transcription factor 1, while inhibiting ERK1 and ERK2 signalling pathway phosphorylation — responsible for regulating cell proliferation. The mixture also disrupted melanoma cell migration.

Glioblastoma and Brain Cancer — The Most Advanced Clinical Evidence

Glioblastoma is the most aggressive form of brain cancer, and it is here that the cannabis-cancer research has produced its most clinically significant result.

These are not marginal differences. They are the kind of numbers that, if replicated in larger trials, would change clinical practice. The biological mechanisms underlying these effects have been studied extensively in the laboratory. Cannabidiol in human and canine glioblastoma cells appears to induce cell death through dysregulation of calcium homeostasis and mitochondrial activity. Synthetic cannabinoids induce autophagy and mitochondrial apoptotic pathways in human glioblastoma cells regardless of deficiencies in TP53 or PTEN tumour suppressors — which matters because those deficiencies often make glioblastoma resistant to standard treatments.

Cannabidiol was also found to trigger autophagy in neuroblastoma cells by regulating the phosphorylation of ERK1 and ERK2, as well as AKT kinases — through a route independent of the mTORC1 pathway. This is relevant because mTOR-independent autophagy is less likely to be blocked by resistance mechanisms that cancer cells commonly develop.

The review also notes that lignanamides — phenylpropionamide derivatives found in Cannabis sativa seeds — significantly inhibited proliferation in a U-87 glioblastoma cell line by inducing apoptosis and suppressing autophagic cell death. This is a reminder that the anticancer chemistry of cannabis extends well beyond the cannabinoids alone. On the anti-angiogenesis side, local administration of a cannabinoid compound in mice inhibited the angiogenesis of malignant gliomas, producing small and impermeable blood vessels in treated tumours, compared to large and porous ones in untreated tumours.

Cholangiocarcinoma — Autophagy as the Primary Mechanism

In human cholangiocarcinoma cells — cancer of the bile ducts — cannabidiol upregulated LC3BII, a key marker of autophagy induction, while downregulating p62, a protein whose reduction indicates that the autophagy process is proceeding. Cannabidiol also inhibited the PI3K, AKT, and mTOR signalling pathways — a central growth and survival axis in many cancers — pushing cells toward autophagic death rather than continued proliferation.

The review also noted that essential oils from a Cannabis sativa cultivar called Tisza showed particularly marked cytotoxicity in cholangiocarcinoma cells in vitro — suggesting that the terpene and terpenophenol profile of the plant, not just its cannabinoids, may contribute to anticancer effects in this cancer type.

Head and Neck Cancer — CBD as a Sensitiser

In head and neck squamous cell carcinoma, cannabidiol increased the expression of genes coding for Beclin and LC3II — two proteins fundamental to the initiation of autophagy. The same study found that cannabidiol enhanced the cytotoxicity of anti-cancer drugs in these cell lines, pointing toward its potential value as an agent that sensitises cancer cells to treatment rather than acting alone. A synergistic effect was specifically documented for the combination of CBD with cannabichromene or THC, where small concentrations of the combination replicated the effect of much higher doses of either compound in isolation.

The Five Mechanisms — How Cannabinoids Attack Cancer Cells

Across all eight cancer types, the research maps onto five distinct biological mechanisms.

The Honest Limitations

An analysis of 207 preclinical articles, including 77 unique case reports, found no strong clinical trial data confirming that Cannabis sativa compounds have proven benefits against cancer in humans across the full range of cancer types studied in the laboratory. The glioblastoma Phase II trial is the exception — a genuinely promising result, but from a group of only 21 patients.

None of this is a reason to dismiss what the laboratory research shows. It is a reason to take it seriously enough to pursue it through the rigorous clinical trial process that will ultimately determine whether cannabinoids earn a formal place in cancer treatment protocols.

What This Means in Practice

The research picture emerging from this review is not one of cannabis as a cure for cancer. It is a picture of a plant producing biologically active compounds that interact with fundamental cancer cell processes in ways that are scientifically credible and, in several cases, reproduced across multiple independent research groups.

The most honest summary of where the evidence stands is this: cannabinoids have demonstrated anticancer properties in laboratory settings across a striking range of cancer types and through five distinct mechanisms. The one clinical trial that has tested a cannabinoid combination alongside standard chemotherapy in brain cancer produced results that are genuinely encouraging. The field now needs larger, better-powered, properly randomised clinical trials to determine which cancers, which compounds, which doses, and which patient populations will actually benefit.

That work is difficult, expensive, and complicated by regulatory frameworks that still treat cannabis as a controlled substance in most jurisdictions. But the scientific case for pursuing it is no longer speculative. It is grounded in a growing body of mechanistic evidence that this review helps to organise and make visible.