In comparison with the MCF-7 cells, usedin most of the studies dealing with breast cancer cellsunder simulated microgravity (5, 10, 11), the evaluatedbiologic features of CRL-2351 cell line in this studyare controversial from many aspects: CRL-2351 cellsare negative estrogen receptor, so the pathways usuallyassociated with estrogen receptor signaling, like MAPkinase, will be influenced in a unique, hitherto unknownmanner. Here, ESR1 is linked to breast cancer.