We’ve focused on establishing the significance on the cell surface hyaluronan receptor CD44 in underpinning the preferential metastasis of breast cancer cells to bone. In prior in vitro research, we demonstrated that depletion of CD44 expression in breast cancer cells attenuates their adhesion to bone marrow endothelial cells. Our recent experiments have also determined that the expression of CD44 is elevated inside the bone homing breast cancer subline MDA231BO relative to that detected within the parental MDA231 breast cancer cell line. With each other these experiments suggest a physiological role for this receptor in promoting the entry of breast cancer cells into the bone microenvironment.
Methods To further fully grasp the potential significance of CD44 signalling to breast cancer metastasis, we established a tetracycline regulated CD44 expression technique in the minimally invasive, CD44 unfavorable MCF7F cell line. Removal of tetracycline from the growth media resulted in time dependent increases in CD44 expression in MCF7F cells, advertising elevated cell invasion and migration selleckchem responses as well as potentiating the adhesion of MCF7F cells to BMECs. Subsequent microarray evaluation was performed utilizing this expression program to determine CD44HA regulated genes in breast cancer cells. Outcomes The expression and activation of CD44 was connected with enhanced expression of a subset of genes implicated in metastasis such as proteolytic enzymes, growth elements and cytoskeletal proteins. Interestingly, the cysteine protease cathepsin K plus the matrix metalloprotease MT1MMP had been identified as CD44HA regulated genes.
These proteases target collagen I, a significant selleck chemical component in the bone matrix whose degradation is a main consequence of osteolytic metastasis of breast cancer. Consistent with their respective metastatic potential, immunoblotting and ELISA primarily based experiments have confirmed that the expression of MT1MMP and cathepsin K are both elevated within the MDA231BO bone homing cells relative to the parental MDA231 cells. Moreover, the expression of cathepsin K and MT1MMP within the MDA231BO cells was significantly decreased upon RNAi mediated suppression of CD44. Quantitative genuine time PCR, immunoblotting and ELISA primarily based experiments have also demonstrated that the transcript and protein expression of cathepsin K and MT1MMP increase in response to CD44HA signalling within a panel of CD44 expressing breast cancer cell lines.
Currently, we are investigating the mechanistic basis underpinning the transcription of those target genes in breast cancer cells, figuring out the functional significance of their overexpression in facilitating breast cancer cells to degrade a collagen I matrix, and applying the MDA231BO cell line to determine the in vivo significance of CD44 expression to osteolytic metastasis.