CIP2A and PP2A in human leptomeninges, arachnoid granulations and meningiomas

CIP2A regulates proliferation and apoptosis of multiple myeloma cells

Multiple myeloma (MM) is one of the most common causes of mortality from hematological malignancy in China. Recent studies have demonstrated that cancerous inhibitor of protein phosphatase 2A (CIP2A) may exhibit a role in promoting the growth of cancer; however, the function of CIP2A in MM remains unknown. In the present study, the expression and molecular mechanism underlying the effects of CIP2A in patients with MM and in MM cell lines were elucidated. Firstly, the expression of CIP2A was detected in patients with MM and in MM cell lines by reverse transcription‑quantitative polymerase chain reaction. Furthermore, silencing of CIP2A with short hairpin RNA was performed in MM cells, and the impact on the proliferation and apoptosis of RPMI‑8226 cells was analyzed (as endogenous CIP2A is highly expressed in RPMI‑8226 cell lines compared with other cells). CIP2A was significantly elevated in patients with MM and in MM cell lines, and silencing of CIP2A could inhibit the proliferation ability of RPMI‑8226 cells in vitro. In addition, CIP2A knockdown induced apoptosis and led to substantial reduction of c‑Myc protein levels in MM cell lines. This study suggested that CIP2A inhibition may provide a promising therapeutic strategy for patients with MM.

MKP-3 regulates PDGF-BB effects and MAPK activation in meningioma cells

Autocrine platelet derived growth factor-BB (PDGF-BB) and cerebrospinal fluid, which also contains PDGF, stimulate proliferation of leptomeningeal and meningioma cells, in part, by activation of the Raf-1-MEK-1-MAPK pathway. The negative regulators of this activation are not known. However, PDGF receptors and p44/42 MAPK are regulated, in part, by mitogen activated kinase phosphatase 3 (MKP-3) and Src homology carboxyl terminus protein (SHP-2). Six fetal and one adult human leptomeninges specimens and 22 meningiomas were evaluated for MKP-3, SHP-2, and phospho-SHP-2 as well as activation/phosphorylation of MEK1/2, p44/42 MAPK, Akt and signal transducer and activator of transcription 3 (STAT3) by western blot and MKP3 expression by polymerase chain reaction. PDGF-BB and cerebrospinal fluid effects on these phosphatases and signaling were also studied in vitro. MKP-3 and phospho-p44/42 MAPK were detected in all or six of seven leptomeninges, respectively. MKP-3 was detected in six of eight World Health Organization grade I and II meningiomas. Three of four grade I and five of five grade II with no or low MKP-3 had high levels of phospho-p44/42MAPK. MKP3 was not detected in four of six grade III meningiomas. These had high levels of phospho-p44/42MAPK. SHP2 was found in all leptomeninges and meningiomas while phospho-SHP-2 was found in 11 to 33% of grade I-III meningiomas. Reduced MKP-3 may facilitate PDGF-BB autocrine and paracrine mitogenic effects in a subpopulation of higher grade meningiomas by increasing phospho-p44/42 MAPK.