SELENOS and cancer: Furthermore, it is also important to underline that some selenoproteins, including SELENOF, SELENOK, SELENOM, SELENON, SELENOS, SELENOT and DIO2, are localized in the endoplasmic reticulum (ER) organelle and involved in protein degradation and regulation of ER stress that has been observed in many types of cancer cells, being associated with cell survival and resistance to anticancer drugs [11].