Sulforaphane and the Anticancer Immune Response

Introduction

Sulforaphane is attracting interest not only because of its effects on cancer cells, but because it may influence the immune environment around them. Researchers have found that it can help cancer-killing cells work more effectively, reduce the activity or survival of certain immune-suppressive cells, and alter signals through which tumours restrain immune attack. Small human studies have begun to explore whether these effects translate into patients.

1. Cancer immunity is all about relationships and context
2. Why sulforaphane entered this conversation
3. An early human clue: changing gene-regulating enzyme activity in blood cells
4. Removing suppression: the MDSC findings
6. A newer human study: lung cancer, chemotherapy and checkpoint immunotherapy
7. Why sulforaphane can enhance some responses while dampening others
8. What a dynamic cancer journey means—and does not mean
The NSAID observation: an unexpected clue, not a proven conflict
9. Why preparation and exposure belong in the interpretation
10. Closing perspective
11. SFN Dosing in Study and Sourcing Discussion
Further Reading and Sources

1. Cancer immunity is all about relationships and context

Imagine a tumour containing immune cells capable of killing cancer cells. Their presence sounds encouraging, but several questions remain: Can they recognise the cancer? Can they reach the relevant cells? Are they equipped to kill? Are neighbouring cells suppressing them? Are inhibitory signals restraining their response?

A tumour is not simply a collection of malignant cells. Its microenvironment also includes immune cells, supporting cells, blood vessels and structural material. Those components can help or hinder immune attack. Sulforaphane research increasingly intercepts these relationships rather than looking only at whether the compound kills cancer cells directly.

Several immune players recur in this research:

• CD8 T cells can recognise and kill cells displaying their particular target.

• Natural killer cells, or NK cells, can kill certain abnormal cells using a different recognition system from T cells.

• Myeloid-derived suppressor cells, or MDSCs, are a varied population that can suppress T-cell responses in cancer.

• Regulatory T cells, or Tregs, help restrain immune responses; within some tumour environments, this can limit anticancer activity.

• Macrophages have diverse functions, including inflammation, tissue repair and support or suppression of tumour-directed immunity. [2,4]

These are never permanently “good” or “bad” populations. Their state, location and interactions matter.

For people living with cancer, this changes the question from “How strong is my immune system?” to “ What is helping—or obstructing—the response needed here?”

2. Why sulforaphane entered this conversation

Sulforaphane is a plant-derived compound formed from its precursor, glucoraphanin, found in broccoli and related cruciferous vegetables. Conversion involves the enzyme myrosinase, supplied by plant tissue or microbial activity in the gut. Different preparations on the market can therefore produce different exposures to sulforaphane and its metabolites.

Its biological effects are broader than a single pathway. Research has examined changes in cellular stress responses, inflammatory signalling, gene regulation and protein turnover. The anticancer immune studies discussed below involve several of these mechanisms.

3. An early human clue: changing gene-regulating enzyme activity in blood cells

In 2015, Lauren Atwell and colleagues published a randomised, double-blind, placebo-controlled study involving 54 women undergoing breast assessment. Participants received a glucoraphanin-containing broccoli-seed extract or placebo between diagnostic biopsy and a later assessment or surgery.

The researchers measured sulforaphane metabolites, breast-tissue biomarkers and HDAC activity in a mixed population of immune cells circulating in the blood, including lymphocytes and monocytes. These are collectively called peripheral blood mononuclear cells, or PBMCs.

What are HDACs?

Histone deacetylases remove acetyl groups from histones—the proteins around which DNA is packaged—and from other proteins. Histone acetylation helps regulate access to DNA instructions. Changing HDAC activity can therefore influence gene regulation, although its consequences depend on the cell and the targets involved.

What changed?

Average PBMC HDAC activity decreased in the supplement group and increased in the placebo group. The difference in change between groups was statistically significant, with p = 0.04. [1] This was the first human signal that exposure to a broccoli-derived preparation could influence a gene-regulating enzyme system in circulating cells.

It was not a demonstration that those cells killed cancer more effectively. The assay examined enzyme activity in a mixed sample, not the behaviour of individual immune-cell populations. Nor did the study find significant supplement–placebo differences in the examined breast-tissue biomarkers after adjustment for multiple comparisons.

It did pave the way for the next step , which was to ask more specific questions: which cells change, which proteins change, and does their behaviour change?

4. Removing suppression: the MDSC findings

One of the clearest mechanistic advances came in a 2024 paper in the Journal for ImmunoTherapy of Cancer. Researchers investigated whether sulforaphane could relieve the suppression imposed by MDSCs.

The situation: cancer-killing cells are present but held back

MDSCs can inhibit T cells through several mechanisms, including inhibitory surface signals, suppressive chemical messengers and changes in the local metabolic environment.

Even when cancer-killing T cells are present, these suppressive signals can prevent them from working effectively. The challenge may therefore be less about producing more T cells and more about reducing the suppression holding them back.

What the experiments showed

In mouse lung-cancer and melanoma models, sulforaphane reduced MDSC accumulation in blood and tumour sites. In cell experiments, it reduced several measures of MDSC suppressive activity, including arginase-1, PD-L1, nitric oxide and reactive oxygen species.

The researchers also tested function: MDSCs normally suppressed CD8 T-cell proliferation; sulforaphane treatment relieved that suppression; and in a co-culture experiment, CD8 T cells recovered a greater ability to kill tumour cells.

This is stronger evidence than a change in a surface marker alone: the investigators measured what the cells did.

How were the suppressor cells affected?

The proposed mechanism involved increased IL-12RB2, reduced MMP3, increased FasL and activation of caspase-3, leading to apoptosis—organised cell death—in MDSCs.

In plain language, sulforaphane helped engage a self-destruct pathway in cells that were restraining the anticancer response.

The study also treated cells obtained from malignant pleural effusions—fluid collected around the lungs of patients with cancer. Similar changes occurred in those patient-derived cells in the laboratory. That provides a bridge towards human biology, but it is still different from demonstrating the same mechanism after a person takes the compound.

What happened in patients?

The paper included blood samples from 10 patients with lung cancer receiving sulforaphane and 10 comparison patients not receiving it. The treated patients showed a reduced proportion of circulating MDSCs, increased IL-12RB2-positive and FasL-positive MDSCs, and CD8 T-cell marker changes consistent with increased activation and reduced inhibitory signalling.

These findings support further investigation. The detailed tumour-killing mechanism, however, rests mainly on cell and animal experiments; this small human component did not establish a survival benefit.

5. Changing inhibitory signals: the CAR-T research

A 2021 study examined CAR-T cells—T cells engineered to recognise a chosen cancer-associated target. The central question was whether sulforaphane could help these cells maintain effective activity against tumour cells.

The situation: an immune attack triggers a counter-response

PD-1 is an inhibitory receptor on T cells. PD-L1, found on tumour cells and other cells, can engage it and restrain the response. IFN-γ released during immune activity can help induce PD-L1 on tumour cells. An immune attack can therefore provoke a counter-signal that limits the attack. [3]

This is one reason the immune environment is dynamic rather than fixed.

What sulforaphane changed

In experiments using mesothelin-targeted CAR-T cells and lung-cancer cells, sulforaphane reduced PD-1 on CAR-T cells, increased release of killing granules, increased perforin and granzyme B, increased IFN-γ, and increased tumour-cell killing.

The investigators linked PD-1 reduction partly to changes in PI3K–AKT signalling. On the tumour-cell side, sulforaphane increased β-TrCP, a protein involved in tagging other proteins for disposal, promoting PD-L1 degradation.

That second finding illustrates why “epigenetic compound” is an incomplete label. PD-L1 protein declined without a corresponding decline in its RNA instruction: the mechanism involved protein turnover, not simply switching off a gene.

How far did this translate?

The study included cell experiments, mouse experiments and an exploratory human comparison of four patients receiving CAR-T therapy plus a broccoli-sprout extract with four receiving CAR-T therapy alone. Human blood measurements showed lower PD-1 and higher IFN-γ and IL-2 in the extract group.

The study supplied a coherent biological argument: sulforaphane affected inhibitory signalling on both sides of the immune–tumour interaction, and those changes accompanied stronger killing in experimental systems.

6. A newer human study: lung cancer, chemotherapy and checkpoint immunotherapy

A 2026 MedComm paper brought several strands of sulforaphane research together. Alongside mouse experiments, it examined whether adding sulforaphane to chemotherapy and anti-PD-1 immunotherapy was associated with better outcomes in people with non-small cell lung cancer. Blood and tumour samples provided an opportunity to investigate not only whether outcomes differed, but what might be changing in the immune response.

What was the study design?

This was a single-centre, prospective observational study—not a randomised trial. The initial analysis included 80 patients: 35 received the sulforaphane combination and 45 received chemotherapy plus anti-PD-1 treatment without sulforaphane. Propensity-score matching, a statistical method intended to improve comparability on measured characteristics, produced two groups of 30.

What preparation and SFN dose was reported?

The supplementary methods report oral “SFN 100 mg/day” from day 1 through day 84—a 12-week course—alongside chemotherapy and anti-PD-1 immunotherapy. The supplier was Pu’er Qiyun Biotechnology Co., Ltd. The schedule specifies a total daily dose, but not whether it was taken once daily or in divided doses.

The treatment duration: Patients were not reported to have continued sulforaphane throughout the longer follow-up. Whether immune effects persisted after the course—and whether that contributed to subsequent outcomes—was not established.

What happened in the blood?

The sulforaphane combination group showed a pattern consistent with a more active, less suppressed anticancer immune response:

Increased proportions of CD8 T cells and CD8 T cells expressing CD69, an activation-associated marker.
Reduced proportions of CD8 T cells expressing the inhibitory receptors PD-1 or CTLA-4.
Reduced proportions of MDSCs expressing suppression-associated markers, including PD-L1 and CD73.
Reduced FOXP3-positive CD4 T-cell fractions, consistent with fewer regulatory T cells by the study’s assay.[ppl-ai-file-upload.s3.amazonaws]

The interesting feature is the combination of changes. This was not simply “more T cells”: it also suggested changes in the signals and neighbouring cells that can restrain them.

These measurements do not prove that every T cell became more effective or that reduced PD-1 meant exhaustion had been reversed. They provide a biological pattern to examine alongside the clinical outcomes. The researchers also identified differences in gene-expression pathways between the groups before treatment, showing that their starting immune environments were not identical.

What did tumour tissue reveal?

Blood gives one view of immunity. Tumour tissue can reveal what is happening where immune cells and cancer cells meet.

Using imaging mass cytometry—a method that identifies multiple proteins and cell types within tissue—the researchers examined immune-cell markers and spatial organisation. They reported higher granzyme B and Ki67 in CD8 T cells and NK cells in the sulforaphane combination group. Granzyme B is part of the machinery used to kill target cells; Ki67 indicates proliferation. They also reported lower PD-L1 on MDSCs and macrophages classified as M2-like.

Together, these observations suggest that some tumour-associated immune cells were more equipped for an active response, while certain suppressive signals were reduced.

However, this part of the study was much smaller than the clinical comparison. The principal tissue-analysis figures show five baseline samples per group and only two post-treatment samples per group. The authors explain that not all patients agreed to another biopsy. These findings are therefore clues about possible mechanisms, not evidence that the same changes occurred throughout the clinical cohort.

The surrounding tissue matters too.

The researchers also examined myofibroblasts—supporting cells that help shape the tissue around a tumour. In the sulforaphane combination group, they reported lower markers of myofibroblast activation, lower collagen I and lower PD-L1 on these cells. They also observed shorter distances between certain immune-cell populations and epithelial cells in the tumour sections.

This adds another dimension to the research. An effective anticancer response depends not only on what immune cells can do, but also on the environment in which they operate.

The findings raise the possibility that the combination influenced both immune activity and the surrounding tissue. The small tissue analysis did not establish that these changes improved immune-cell access or caused the better clinical outcomes.

Were clinical outcomes different?

The reported results were encouraging:

Outcome	Sulforaphane combination	Chemotherapy plus anti-PD-1 treatment
Objective response rate	86.7%	60.0%
Median progression-free survival	19 months	9.5 months

The objective response rate measures the proportion of patients whose tumours shrank enough to meet defined response criteria. Progression-free survival measures time without documented disease progression or death. The reported progression-free-survival hazard ratio was 0.45, with a 95% confidence interval of 0.23–0.88.

These findings deserve attention because they place immune measurements alongside meaningful patient outcomes.

Safety findings need to be read in the context of the full three-part regimen. The sulforaphane combination group experienced more grade 3–4 anaemia, while liver and kidney measurements were broadly reassuring. These results do not establish that sulforaphane caused the anaemia, but neither do they establish that adding it was free of side effects.

Two "pseudo-progression" imaging findings

Two patients in the sulforaphane combination group developed new lung lesions during treatment—one after 15 months and another after the fourth treatment cycle. Biopsies showed inflammatory changes or necrosis, and the lesions subsequently shrank while the original treatment continued. The authors interpreted these events as pseudo-progression.

These cases illustrate why a new imaging abnormality during immunotherapy sometimes requires further assessment. They do not establish that sulforaphane caused pseudo-progression, and they are not a reason to assume that new lesions represent an immune response rather than cancer growth. The authors acknowledge that sulforaphane’s role is uncertain.

What does this study add?

Its value lies in connecting several levels of observation: clinical outcomes, circulating immune cells and the tumour environment. Rather than looking only for direct cancer-cell killing, it explores whether sulforaphane could help create conditions in which chemotherapy and checkpoint immunotherapy work more effectively.

The results give researchers a concrete reason to pursue larger randomised studies, with clearly documented formulations and dosing, inclusion of patients who stop treatment early, and more complete tissue sampling. This study also builds on the same research programme as the earlier CAR-T and MDSC papers. That continuity is really valuable.

7. Why sulforaphane can enhance some responses while dampening others

The enhancing findings are not the whole story.

A 2026 study exposed Jurkat cells—a human T-cell leukaemia-derived laboratory model—to sulforaphane before artificially activating them. Sulforaphane reduced IL-2 secretion and several activation-associated surface proteins. IL-2 suppression was significant from 3 µM, while many surface-marker effects occurred at higher concentrations. Cell viability also declined at some of the highest exposures.

This was not a human trial, and Jurkat cells are not interchangeable with T cells in a patient. Nevertheless, it demonstrates that directly exposing a T-cell model to sulforaphane can suppress activation rather than enhance it.

Three situations help make sense of the difference

Situation A: The tumour environment is actively suppressing T cells. Reducing MDSC survival or suppressive MDSC activity may let T cells work more effectively. The net result can be increased tumour-directed activity even if the compound is not a universal T-cell stimulant. [2]

Situation B: Inhibitory signalling is limiting an ongoing response. Changing PD-1 on T cells or PD-L1 on tumour cells may alter the balance between attack and restraint. This was investigated in the CAR-T experiments. [3]

Situation C: The compound acts directly on a cell’s activation machinery. It makes sense that exposure to SFN before activation may reduce the signals and cytokines needed to mount a response and this is what the Jurkat study examined. [5]

These situations differ in cell type, timing, concentration, activation state and neighbouring cells. They should not be compressed into a single claim that sulforaphane “strengthens” or “weakens” immunity.

Reducing an immune response is not automatically helpful or harmful—it depends on the context and what that response is doing.
Checkpoint immunotherapies, such as anti-PD-1 treatments, block inhibitory signals that restrain our T cells from attacking cancer. But these immunotherapy treatments can also cause immune cells to attack healthy tissue—for example, causing inflammation of the bowel, known as colitis. Doctors may then use corticosteroids or other immune-suppressing medicines to control that harmful response.
The goal is therefore not simply “more immunity” or “less immunity,” but effective activity against cancer without damaging healthy organs.

This example illustrates the balance involved in immunotherapy; it does not establish that sulforaphane can prevent or treat its inflammatory side effects, or selectively dampen harmful responses while preserving beneficial ones.

8. What a dynamic cancer journey means—and does not mean

The immune response around a tumour can contain competing processes at the same time. An active T cell can produce signals that help fight cancer while also provoking an inhibitory response from nearby tumour cells. Suppressive myeloid cells may coexist with cells equipped to kill. Treatment can change those relationships, making “immune support” a much more specific concept than it first appears.

Helping an immune cell act on a recognised target, removing neighbouring cells that suppress its activity, reducing inhibitory signals, changing access to the tumour, or limiting inflammation that is not producing useful tumour control are all important considerations of oncology researchers today.

The sulforaphane studies are exciting in that they investigate important parts of this landscape.

Patients and practitioners cannot determine which mechanism dominates from fatigue, symptoms or a routine white-blood-cell count alone. The studies discussed here used specialised cell assays, molecular measurements and, in some cases, tumour-tissue imaging. [1,2,4]

The practical takeaway is not “choose whether to stimulate or suppress your immunity.” It is that a useful immune response depends on the right cells doing the right job in the right setting and what can we do to support this.

The NSAID observation: an unexpected clue, not a proven conflict

The 2015 breast study contained a detail that complicates a simple HDAC story.

Participants reporting NSAID use—non-steroidal anti-inflammatory drug use—were unevenly distributed between groups, with significantly more users in the supplement group. Researchers adjusted for this and also examined users and non-users separately.

For all participants, the difference in change in PBMC HDAC activity between supplement and placebo was significant (p = 0.04). Among participants not using NSAIDs, the difference was also significant (p = 0.04). Among participants using NSAIDs, no statistically significant supplement–placebo difference was detected.

This finding concerned enzyme activity in mixed blood cells—not anticancer immune function.

What might explain it?

The authors proposed that NSAID-related changes in prostaglandin signalling might alter HDAC recruitment to chromatin, potentially counteracting or obscuring the effect associated with sulforaphane exposure. They did not measure that full mechanism in participants. It was a hypothesis offered to explain the observation.

What does the result not prove?

A statistically significant result in one subgroup and a non-significant result in another do not, by themselves, prove the treatment effects differ. Differences in subgroup size and variability can produce that pattern.

The article reports the separate blood-cell subgroup findings without a formal interaction-test result establishing that NSAIDs changed the HDAC treatment effect. Its separately reported interaction tests for breast-tissue biomarkers were not significant. NSAID use itself was not randomised.

The appropriate conclusion is that background medication use may help explain variation in a measured epigenetic response. This small study did not establish that NSAIDs block sulforaphane’s anticancer effects.

It provides no basis for stopping aspirin or another prescribed NSAID. It does provide a useful reminder that compounds act within an existing biological and medication environment.

9. Why preparation and exposure belong in the interpretation

“Sulforaphane” studies do not all test the same intervention.

Some use purified compound in culture. Some inject it into mice. Human studies have used broccoli-derived extracts, glucoraphanin preparations or extracted sulforaphane capsules. Conversion, absorption, metabolism and exposure duration can differ. [1–3]

In a human absorption study, fresh broccoli sprouts and a myrosinase-treated extract supplying the same nominal sulforaphane amount produced substantially different measured metabolite exposures. This illustrates why a label amount cannot simply be equated with the concentration bathing a cell in a laboratory dish. [6]

Exposure differences can help explain apparently inconsistent findings. They also prevent the research from being translated into a generic dose recommendation.

Have you read the report on: Why natural medicines often lack large clinical trials".

10. Closing perspective

The most interesting possibility is not that sulforaphane makes every immune cell more active. It is that, in some settings, it may change the conditions under which an anticancer response succeeds: fewer suppressive cells, altered inhibitory signals and better-equipped tumour-directed cells. Experimental studies support those possibilities, and early human work gives them increasing relevance. [2–4]

At the same time, its ability to dampen activation in other systems is not an awkward detail to hide. It is part of the explanation. A cancer journey involves changing relationships between tumour, treatment and immune response—not a single immune dial waiting to be turned up.

11. SFN Dosing in Study and Sourcing Discussion

Study and participants	Preparation and dose	Schedule and duration	Findings and limitations
Shapiro et al., 2006—phase I safety/metabolism study; 12 healthy volunteers in three cohorts, each with three active-treatment participants and one placebo participant	Approximately 13.3 mg/day as SFN equivalents	Participants in the sulforaphane-rich group received 7.5 mL of liquid extract every eight hours for seven days.	No significant or consistent treatment-associated toxicities were observed. Urinary metabolite recovery was substantially higher with the isothiocyanate-rich preparation than with the glucosinolate-rich preparations. This was a short safety/metabolism study—not a cancer-treatment trial.
Cipolla et al., 2015—double-blind, randomised, placebo-controlled trial; 78 men analysed with rising PSA after radical prostatectomy	60 mg/day of stabilised free SFN, supplied as Prostaphane tablets. Each tablet contained 10 mg SFN.	Two tablets (20mg) three times daily for six months, followed by two months without treatment.	The primary endpoint was not reached. Secondary findings included a smaller PSA increase and longer PSA doubling time: 28.9 vs 15.5 months.
Traka et al., 2019—ESCAPE randomised, double-blind, three-arm trial; 61 men randomised, 49 completed, with 48 included in the principal tissue analysis	A 300 mL broccoli soup	One portion weekly for 12 months. An optional extension continued to 24 months, but the paired biopsy investigation covered the first 12 months.	Higher-glucoraphanin soups attenuated changes in prostate gene expression associated with potentially cancer-promoting pathways. The study was not designed or sufficiently powered to establish reduced clinical progression.
Shen et al., 2021—CAR-T study; four patients received extract plus CAR-T and four received CAR-T alone	2 x broccoli-sprout extract: capsules/day. The paper does not specify the actual SFN amount per capsule or per day.	Oral dosing for 30 days, beginning at the start of CAR-T therapy. Whether the capsules were taken together or separately is not stated.	Lower PD-1 expression and higher IFN-γ and IL-2 expression were observed in circulating CD8 CAR-T cells.
2026 NSCLC study—SFN added to chemotherapy + anti-PD-1 immunotherapy; 35 vs 45 initially, with 30 per group after matching	100mg/day free SFN orally. Unclear if spread out over the day or taken in one dose.	Daily on days 1–84: 12 weeks.	Median PFS was 19 months vs 9.5 months; objective response rates were 86.7% vs 60.0%.

Recapping the key 2026 human chemotherapy + anti-PD-1 immunotherapy study above: They reported using SFN 100 mg/day” from day 1 through day 84—a 12-week course—alongside chemotherapy and anti-PD-1 immunotherapy. This is not 100mg broccoli sprout powder but 100mg of the actual free Sulforaphane.

The study group's trusted supplier of the highest purity and most bioavailable compounds for cancer patients makes a unique supplement called Broccoli Ultra. It is unique in that that unlike other powders on the market it was created for cancer patients and it contains 15mg of free Sulforaphane per capsule (equiv. to 357mg per capsule of sulforaphane glucosinolate found in other brands/capsules).

To match the Cipolla et al., 2015 prostate cancer PSA trial this would look like 4 x Broccoli Ultra per day and
6-7 x Broccoli Ultra per day matches the chemotherapy + anti-PD-1 immunotherapy dosing.
The Shen et al., 2021 4 CAR-T study likely requires just 1-2 x Broccoli Ultra per day.

You will find the link to Broccoli Ultra, alongside our group members 5% discount code 'abbey5' here on the Trusted Suppliers and Discounts page.

Taking 6 capsules (3 twice a day with food) of Broccoli Ultra, per day provides 90mg free Sulforaphane (or the equiv. of 2,250mg of sulforaphane glucosinolate found in other brands/capsules). Some patients might be aiming for higher dosing depending on their individual treatment or maintenance protocols. Six capsules lands you just under the chemotherapy + anti-PD-1 immunotherapy study dose and seven, just over.

Tumor burden and the persons body mass might help decide on exact daily dose. Most members start with one capsule with each meal for first few days and increase dose every few days per individual gut response.