It’s long been known that the phytochemical lycopene is helpful for prostate health. But it’s not just men who can benefit from this carotenoid, which is found in tomatoes, watermelon, guava, papaya, red grapefruit and red peppers. Lycopene is a powerful antioxidant, can help protect against sunburn, and may also play a role in lowering LDL cholesterol via mild inhibition of HMG-CoA reductase as well as increased LDL receptor synthesis. (You can read more about these properties of lycopene in this DFH article.) A new and emerging area of research for lycopene is in helping to fight cancer.
But first, a quick intro to what lycopene is. It’s a polyunsaturated hydrocarbon with a molecular formula of C40H56. It has a very high antioxidant capacity against singlet oxygen and peroxyl radicals. Lycopene is technically a carotenoid but unlike its cousin, beta-carotene, lycopene has no vitamin A activity. Lycopene in tomato paste is more bioavailable than that from fresh tomatoes, so this may be a rare example of a “processed” food offering benefits above those seen with a fresh, whole food. (Depending on one’s definition of “processed” food, that is.) Additionally, like other carotenoids, lycopene is lipophilic and is best absorbed when consumed with fat. So, combining tomato sauce with cheese or olive oil might be a happy coincidence of gustatory pleasure melding with biological utility.
Some of the interest in lycopene as an adjunct to conventional cancer care comes from its classification as a “botanical radioprotector.” Lycopene is the most potent antioxidant among common carotenoids, edging out beta-carotene, alpha-tocopherol and lutein. With uncontrolled oxidative stress being a major factor associated with increased cancer risk, lycopene could be a powerful ally in potentially reducing this risk. Animal and in vitro studies have shown that incubation or pre-treatment with lycopene protects normal lymphocytes against radiation-induced cellular damage. Owing to lycopene’s abundance, low cost and minimal side-effects, researchers have said the compound is “a favorable radio-protectant.”
Lycopene is being explored for its potential in reducing or preventing the side effects of chemotherapy, owing to its antioxidant effects. Overwhelming production of reactive oxygen species (ROS) may be one factor behind chemotherapy-induced toxicity, so if lycopene could potentially reduce damage to healthy cells and tissues, there may be a role for lycopene in cancer care. Apart from its own effects in this area, lycopene induces endogenous cellular antioxidant enzymes.
Beyond lycopene’s obvious role in ROS scavenging, other mechanisms hypothesized to underlie its potential anticarcinogenic effects include upregulation of detoxification systems, interference with cell proliferation, induction of gap-junction communication, and inhibition of cell cycle progression.
Cancers are easier to treat when they’re localized to one tissue and have not spread. Lycopene may play a role in inhibiting tumor cell migration owing to effects on tight junction proteins. The mechanisms are not yet well understood, but lycopene upregulates ZO-1 (zonula occludens-1), which is a scaffold protein, and downregulates claudin-1, another type of cellular adhesion molecule. Incubation with 10 μM lycopene for 24 hours inhibited cell migration in a human cutaneous squamous cell carcinoma line (COLO-16), but not in healthy human epidermal keratinocytes nor the immortalized human keratinocyte cell line HaCaT. The researchers stated, “These data demonstrated that the inhibitory effect on cell proliferation and migration is stronger in keratinocyte-derived cancer cells compared to normal keratinocytes.” Precisely what we would want to see in a chemotherapeutic agent: inhibition of tumor cell migration with lesser effects on healthy cells.
It must be noted that this research is highly preliminary and much of it has been conducted in vitro. There are several plausible mechanisms for lycopene’s potential role in chemoprotection or chemoprevention, but at this time there is little certainty about which mechanisms are responsible for the observed effects. So it may be premature to encourage increased lycopene consumption for the particular goal of reducing the spread of cancer, but considering the other numerous benefits of this compound, there’s no obvious downside to people enjoying tomato sauce, red peppers, and other foods that are rich in lycopene.