The CaSR is really a G protein coupled receptor activat ing several signaling pathways that are identified to regu late cell proliferation, differentiation, migration and apoptosis. The PI3K AKT pathway, the PLC? 1 pathway plus the MAPK cascades are downstream targets with the CaSR. In our study, calcium remedy resulted inside a clearly enhanced activity of AKT PKB and PLC? 1 in bone metastasizing cells but not in non metastasizing cells. Furthermore, in bone me tastasizing cells, calcium had an activating impact on the MAP kinases p38 and JNK. The focal adhesion adapter protein paxillin also as c Jun, both downstream targets of JNK, showed comparable activity patterns. Inhi biting CaSR with NPS 2143 these enhancements have been pre vented plus the phosphorylation of your signal mediator with all the highest calcium sensitivity, AKT, was reduced.
The further reduction of AKT activity right after inhibition of CaSR indicates a basement activity selelck kinase inhibitor of CaSR even without adding calcium. The culture medium includes a low amount of calcium not specified by the company. Presumably this low calcium concentration results in a slightly activation of CaSR and consequently also of AKT phosphorylation. This impact seems to become inhibited by NPS 2143. The decreased AKT activity induced by NPS 2143 remedy confirms the responsibility of CaSR for the calcium dependent effects. In contrast, calcium had no activating effect on ERK. This suggests AKT, PLC? 1, p38 and JNK paxillin signaling path strategies, which are described as downstream targets of CaSR, being the important pathways in the CaSR signaling in RCC cells advertising bone particular metastasis.
Even so, ERK as a downstream target of CaSR is discussed controversially and some research hypothesize the ERK pathway getting in volved in extracellular calcium induced GDC-0199 cell migration, once again confirming a cell type distinct function of CaSR as already described. The principle regulator of the AKT pathway will be the tumor suppressor PTEN. As an antagonist of the PI3Kinase, PTEN inhibits the activa tion of AKT and thereby down regulates cell prolifera tion and migration. Additionally, in our former investigations we established a correlation amongst low PTEN expression in specimens of RCC sufferers and poor prognosis caused by metastasis. In bone me tastasizing RCC cells, PTEN expression was approxi mately 50% lower than in non metastasizing cells.
The expression of PTEN correlated inversely using the activ ity of AKT. Also, the expression of PTEN was very calcium sensitive. Calcium treatment resulted in an nearly comprehensive decline in the expression of PTEN. This implicates that the per se low PTEN expression in bone metastasizing RCC cells is further decreased by the bone microenvironment, consequently activating the AKT signaling pathway and promoting bone metastasis.