One of the most common drugs used to treat breast cancer is tamoxifen. It works by blocking the activity of estrogenA steroid sex hormone. Estrogen's structure is closely related to cholesterol. Produced by the ovaries, estrogen has effects on the reproductive, cardiovascular and skeletal systems. Estrogen is also a growth factor for some types of cells, including breast cells. Inhibitors of estrogen function such as tamoxifen and arimidex are used to block the growth effects of estrogen. See also, estrogen receptor., reducing the growth of cancer cells. Despite the success of tamoxifen, many cancers eventually become resistant to its effects. The resistance has been shown to be linked to mitochondria Mitochondria are subcellular organelles responsible for extracting the bulk of the energy we use from the food we eat. As a byproduct, oxygen radicals (reactive chemicals) are produced that may contribute to cancer formation by damaging DNA. A mitochondrion (the singular version of the word) is filled with inner membranes upon which the last stages of energy generation take place., small cellular structures that are the source of cellular energy. Specifically the resistance was linked to the activity of a single geneA stretch of DNA that leads to the production of an RNA. The RNA is produced during the process of transcription. This RNA can be used to guide the formation of a protein via translation or can be used directly in the cell. - NQ01. Importantly, inhibitors of NQ01 exist, and testing showed that tamoxifen resistance was reversible in a lab model, opening up the possibility of reversing drug resistance in humans.
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