The CaSR is really a G protein coupled receptor activat ing quite a few signaling pathways that are known to regu late cell proliferation, differentiation, migration and apoptosis. The PI3K AKT pathway, the PLC? 1 pathway plus the MAPK cascades are downstream targets of your CaSR. In our study, calcium treatment resulted in a clearly enhanced activity of AKT PKB and PLC? 1 in bone metastasizing cells but not in non metastasizing cells. Moreover, in bone me tastasizing cells, calcium had an activating effect around the MAP kinases p38 and JNK. The focal adhesion adapter protein paxillin too as c Jun, both downstream targets of JNK, showed comparable activity patterns. Inhi biting CaSR with NPS 2143 these enhancements were pre vented as well as the phosphorylation of the signal mediator using the highest calcium sensitivity, AKT, was lowered.
The further reduction of AKT activity immediately after inhibition of CaSR indicates a basement activity selleck of CaSR even with out adding calcium. The culture medium includes a low level of calcium not specified by the enterprise. Presumably this low calcium concentration leads to a slightly activation of CaSR and consequently also of AKT phosphorylation. This impact seems to be inhibited by NPS 2143. The reduced AKT activity induced by NPS 2143 therapy confirms the responsibility of CaSR for the calcium dependent effects. In contrast, calcium had no activating impact on ERK. This suggests AKT, PLC? 1, p38 and JNK paxillin signaling path strategies, which are described as downstream targets of CaSR, being the essential pathways within the CaSR signaling in RCC cells advertising bone precise metastasis.
Nonetheless, ERK as a downstream target of CaSR is discussed controversially and some studies hypothesize the ERK pathway being in volved in extracellular calcium induced selleck PLX4032 cell migration, once more confirming a cell variety certain function of CaSR as already described. The main regulator of the AKT pathway is 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. Also, in our former investigations we established a correlation involving low PTEN expression in specimens of RCC patients and poor prognosis brought on by metastasis. In bone me tastasizing RCC cells, PTEN expression was approxi mately 50% decrease than in non metastasizing cells.
The expression of PTEN correlated inversely together with the activ ity of AKT. Additionally, the expression of PTEN was highly calcium sensitive. Calcium treatment resulted in an pretty much total decline inside the expression of PTEN. This implicates that the per se low PTEN expression in bone metastasizing RCC cells is additional decreased by the bone microenvironment, consequently activating the AKT signaling pathway and promoting bone metastasis.