“The use of natural, synthetic, or biologic chemical agents to reverse, suppress, or prevent carcinogenic progression to invasive cancer.”1
With cancer, the best form of cure is prevention. Along these lines, researchers are always looking for methods to prevent cancer. Chemoprevention is the ability of an agent to prevent cancer, often by activating innate cellular pathways that help to hold off malignancies.
Chemopreventative sources that are naturally occurring in our food have immense potential to safely and effectively help to aid in the fight against cancer. One recent natural agent that has shown promise in chemoprevention is sulforaphane. Sulforaphane is an isothiocyanate derived from cruciferous vegetables.
It results in the activation of nuclear factor erythroid 2-related factor 2 (Nrf2).2 Nrf2 then activates a plethora of cancer-fighting genes and pathways, including regulating the body’s response to oxidative stress. In fact, Nrf2 protects our pancreatic cells from oxidative damage, which can lead to pancreatic dysfunction and eventual diabetes.3 Nrf1 and 2 activate what is known as the human antioxidant response pathway to activate NAD(P)H and other cellular responses to detoxify potentially damaging elements within our cells.4 It is our body’s innate detoxification system.
Fighting Breast Cancer with Broccoli
Cruciferous vegetables, like broccoli and Brussels sprouts, also contain significant amounts of glucosinolates. These compounds lead to the pungency of cabbage and mustard plants and are considered a large group of sulfur-containing glucosides.5 These plants also contain the enzyme myrosinase, and when chopped prior to cooking or chewed during consumption, myrosinase releases isothiocyanates.
These cancer-fighting enzymes apparently can stop cancer cell replication and aid in apoptosis, which is the controlled death of cancer cells. The bacteria within our gastrointestinal tract also break down glucosinolates to isocythianates.6 A molecule within the isocyothianate is sulforaphane, which actually serves to help defend the body from cancer.
The glucosinolate precursor of sulforaphane, glucophanin, has been shown to block the formation or progression of breast cancer in rat studies.7 A recent pilot study in eight healthy women gave them a single dose of broccoli sprout preparation containing sulforaphane prior to a breast reduction surgery. The broccoli extract was consumed about 100 minutes prior to the operation. They found that levels of sulforaphane, via the measurement of DTC, increased significantly in the urine from 4.07 to 158.85 μM. Mean blood levels were also raised from 0.01 to 0.92 μM.
However, and perhaps most importantly, they found the presence of sulforaphanes within the breast tissue, presumably from the isothiocyanate concoction with a mean breast tissue DTC concentration of 1.45 and 2.00 pmol/mg tissue for the right and the left breast, respectively.8
While the tissue concentration was unknown before the surgery, mouse studies from the same group revealed an uptake of sulforaphane in their mammary tissue. This uptake then led to the induction of several pathways and gene transcripts that apparently protect our cells from developing cancer, including the NQO1 and HO-1 pathway. The NQO1 pathway is the same pathway described above to offset oxidative damage, that forms NAD(P)H to protect our cells against harmful mutations that can eventually lead to cancer.9
Is Broccoli Actually Toxic to Our Cells?
Some fascinating research points to these aspects of vegetables as being slightly toxic to our cells, which results in a form of hormesis to upregulate these pathways which can eventually fight cancer. Sulforaphane is actually an oxidant, which is why it activates Nrf2 and several antioxidant pathways within our cells. In a sense, this is similar to exercise, an activity that stresses our body to make it “stronger” in the long run. Similar stresses can upregulate the mitochondria, an organelle that is important in the fight against cancer.10
Along these lines, corresponding benefits occur from exercise, which creates free radicals that upregulate our mitochondria to produce our own antioxidants to offset the damage.11 Cancer cells themselves have actually proved to have overactive levels of some of these pathways, potentially further stressing their importance for survival.9
Enthusiasm for Chemoprevention within the Medical Field
The University of Pittsburgh Medical Center, where I practice as a radiation oncologist and an assistant professor, is currently testing the potential of chemoprevention. It recently presented its findings at the American Association of Cancer Research, where Dr. Bauman first showed that a sulforaphane-rich broccoli sprout extract prevented oral cancer in mice. She then conducted a study in 10 healthy human volunteers revealing the extract to be safe with decreased damage to their mucosal lining. A larger study is currently underway to assess a proposed reduction in the risk of oral cancer in 40 volunteers.
The Power of Food
The potential chemopreventative properties of food and food compounds further illustrates the power of food, and in this case, cruciferous vegetables…
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3. Fu J, Zheng H, Wang H, et al. Protective Role of Nuclear Factor E2-Related Factor 2 against Acute Oxidative Stress-Induced Pancreatic β -Cell Damage. Oxid Med Cell Longev. 2015;2015:639191. doi:10.1155/2015/639191.
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8. Cornblatt BS, Ye L, Dinkova-Kostova AT, et al. Preclinical and clinical evaluation of sulforaphane for chemoprevention in the breast. Carcinogenesis. 2007;28(7):1485-1490. doi:10.1093/carcin/bgm049.
9. Belinsky M, Jaiswal AK. NAD(P)H:quinone oxidoreductase1 (DT-diaphorase) expression in normal and tumor tissues. Cancer Metastasis Rev. 1993;12(2):103-117. http://www.ncbi.nlm.nih.gov/pubmed/8375015. Accessed May 8, 2015.
10. Schulz TJ, Thierbach R, Voigt A, et al. Induction of Oxidative Metabolism by Mitochondrial Frataxin Inhibits Cancer Growth: OTTO WARBURG REVISITED. J Biol Chem. 2006;281(2):977-981. doi:10.1074/jbc.M511064200.
11. Ristow M, Zarse K, Oberbach A, et al. Antioxidants prevent health-promoting effects of physical exercise in humans. Proc Natl Acad Sci U S A. 2009;106(21):8665-8670. doi:10.1073/pnas.0903485106.
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