Recent research has revealed intriguing roles for PIWI proteins, traditionally linked to germline development, in various cancers, including colorectal cancer (CRC). In our study, we discovered that PIWIL1 is expressed at high levels in CRC samples and cell lines, where it dramatically relocates to the centrosome during mitosis.

Our findings show that when PIWIL1 is knocked down, it leads to G2/M cell cycle arrest and disrupts the mitotic spindle, causing abnormal metaphase events. This highlights its crucial role in cell cycle progression. Interestingly, PIWIL1 expression diminishes as Caco-2 cells differentiate into enterocytes, yet it is present in the intestinal crypts of healthy human colon tissue, where stem cells reside. This suggests that PIWIL1 might play a role in maintaining stem cells, hinting at a potential connection to the stem cell origin of CRC.

Moreover, our research indicates that the dedifferentiation of human fibroblasts into induced pluripotent stem cells involves the reactivation of PIWIL2, another member of the PIWI family. This expands the understanding of PIWI proteins beyond their traditional roles, pointing to their involvement in somatic stem cell maintenance and their impact on cancer progression.

Overall, our study sheds light on the dynamic role of PIWIL1 in colorectal cancer and suggests broader implications for the PIWI protein family in stem cell biology.