Cucurbitacins are compounds that confer a bitter taste to cucurbits such as cucumbers, squash, and pumpkins. They are produced by plants to protect them from predation by herbivores. Cucurbitacins have cytotoxic properties, which can result in poisoning if consumed in large or concentrated amounts.
However, several cucurbitacins (cucurbitacin B, cucurbitacin D, cucurbitacin E, and cucurbitacin I) have been shown to have a variety of anti-cancer effects. Now a new study has reported that cucurbitacin D has similar effects to the chemotherapy drug Adriamycin (doxorubicin) in three types of breast cancer cells.

Food sources of cucurbitacin D

Cucumbers and winter squashes such as butternut, acorn, and spaghetti squash are the best potential sources of cucurbitacin D. However, because selective breeding has eliminated most of the bitter taste characteristic of the ancestral cucurbits, most cucumbers and squashes are very low in, or entirely free of, cucurbitacins. The skins generally have the highest levels.
Organically grown slicing cucumbers (the common cucumber found in supermarkets) appear to be the best choice. Pickling cucumbers and gherkins also incorporate cucurbitacin D. Burpless cucumbers such as Persian and English cucumbers have low levels of cucurbitacins, including cucurbitacin D. Conventionally-grown cucumbers typically incorporate a variety of pesticides, not all of which can be washed off. In addition, such cucumbers normally are waxed. This wax may be petroleum-based and can trap pesticide residue and other contaminants. Therefore, conventionally grown cucumbers should always be peeled, which eliminates the best source of cucurbitacin D.
Cucurbitacin D and Chinese Cucumber supplements should be avoided because of potential liver damage and harmful interactions with prescribed drugs.

Latest research finds cucurbitacin D has anti-breast cancer effects

The study referenced above was designed to investigate the effects of cucurbitacin D on the viability of breast cancer cells and the mechanism of action. To conduct the study, the authors compared the effects of cucurbitacin D and the chemotherapy drug Adriamycin in MCF-7 (ER+/PR+), SKBR3 (HER2+), and MDA-MB-231 (triple negative) breast cancer cells.
Cucurbitacin D and Adriamycin both were found to increase p53 expression in all three types of breast cancer cells. P53 is a tumor suppressor protein whose activation results either in cell death or DNA repair. Normally, p53 prevents the progression of cells with incorrect numbers of chromosomes toward cancer. Cucurbitacin D also was found to suppress the expression of p-Akt, p-NF-κB, and p-Stat3 expression in all three cell lines. The Akt/mTOR signaling pathway has been shown to play a critical role for survival and proliferation of cancer cells, particularly cancer stem cells. Adriamycin alone did not decrease p-Akt and p-Stat3 levels. The combination of Adriamycin and cucurbitacin D was found to increase p53 levels and suppress Akt, NF-κB, Stat3, and Bcl-2 expression more than cucurbitacin D alone. The authors conclude that cucurbitacin D has the potential to be an effective treatment for breast cancer.