PI3K/p110δ is a novel therapeutic target in multiple myeloma

Abstract

In this study, we demonstrate expression and examined the biologic sequelae of PI3K/p110␦ signaling in multiple myeloma ( IntroductionThe bone marrow (BM) microenvironment plays a crucial role in pathogenesis of multiple myeloma (MM) by promoting cell proliferation, survival, migration, and drug resistance. [1][2][3][4] The PI3K/AKT pathway mediates growth and drug resistance in MM cells and also plays a significant role in autophagy. 5,6 PI3K is activated via upstream tyrosine kinase-associated receptors for growth factors, cytokines, antigens, and costimulatory molecules. It in turn activates AKT, which mediates cell proliferation, cell cycle, apoptosis, and autophagy. 7 Class IA PI3K consists of 5 isoforms of regulatory subunits (p85␣, p50␣, p55␣, p85␤, and p55␥), which interact with class IA isoforms. Class IA PI3K is composed of p110␣, -␤, and -␦ isoforms. 8 Among the 8 distinct mammalian isoforms of PI3K, class I PI3Ks are responsible for Akt activation. Importantly, p110␦ is expressed in many cancers, including colon and bladder carcinoma, glioblastoma, and acute myeloid leukemia blasts. 9,10 In the current study, we demonstrate high expression of p110␦ in patient MM cells. Previous studies have shown that CAL-101, a potent and selective p110␦ inhibitor, has broad antitumor activity against cancer cells of hematologic origin. 11,12 Moreover, inhibition of p110␦ induces cleavage of caspases and LC3, consistent with apoptotic and autophagic cell death, respectively. Here we show that p110␦ blockade with CAL-101, a potent and selective p110␦ inhibitor, inhibits MM cell growth even in the presence of interleukin-6 (IL-6), insulin-like growth factor-1 (IGF-1), or bone marrow stromal cells (BMSCs), associated with decreased phosphorylation of AKT and P70S6k. We also confirmed inhibition of human MM cell growth triggered by p110␦ inhibition in our xenograft mouse models of human MM. These studies therefore show that small molecule inhibitors of p110␦ trigger significant anti-MM cytotoxicity both in vitro and in vivo, providing the framework for their clinical evaluation to improve patient outcome in MM. Methods Materialsp110␦ inhibitor CAL-101 and IC488743 were provided by Calistoga Pharmaceuticals. CAL-101 was dissolved in dimethyl sulphoxide at 10mM and stored at Ϫ20°C for in vitro study. IC488743 was dissolved in 1% carboxyl methylcellulose/0.5% Tween 80 and stored at 4°C for in vivo study. Recombinant human p110␣, ␤, ␥, and ␦ were reconstituted with sterile phosphate-buffered saline (PBS) containing 0.1% bovine serum albumin. Bortezomib was provided by Millennium Pharmaceuticals. 3-Methyladenine was purchased from Sigma-Aldrich. The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked ''advertisement'' in accordance with 18 USC section 1734. Cell culture Dex 1460BLOOD, 2 SEPTEMBER 2010 ⅐ VOLUME 116, NUMBER 9For personal use only. on March 28, 2019. by guest www.bloodjournal.org From Germany). LB human MM ce...

A Novel Role for Bruton's Tyrosine Kinase in Hepatocyte Growth Factor-mediated Immunoregulation of Dendritic Cells

“…We have previously reported that these two PI3K complexes are required for HGF-induced inhibition of DCs (23). Our findings are noteworthy in view of the fact that suppression of DCs by HGF weakens the anti-tumor efficacy of DC-based immunotherapy in MM, and a very recent report suggesting PI3K/p110␦ as a novel therapeutic target for MM (13,46). Notably, an increased Btk expression in a human MM cell line resistant to dexamethasone, a drug commonly used for MM treatment, has also been demonstrated (47).…”

The PI3K/Akt signaling pathway regulates the expression of Hsp70, which critically contributes to Hsp90-chaperone function and tumor cell survival in multiple myeloma

“…The PI3K/Akt pathway has drawn considerable attention as a promising therapeutic target in MM. [21][22][23] It is, therefore, conceptually intriguing that PI3K inhibition might serve as a useful strategy to target the HSF1/Hsp72 axis. This is of immediate clinical relevance because -in contrast to the situation with Hsp70 -the development of therapeutically suitable PI3 kinase inhibitors is quite advanced.…”

“…We, therefore, explored the potential regulation of Hsp70 by different signaling pathways including the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, which is frequently activated in MM and contributes to tumor cell survival. [21][22][23] Two different experimental approaches were pursued to inhibit PI3K-mediated signaling: pSUPER-based siRNAmediated knockdown of the p110α subunit of PI3K ( Figure 4A) and treatment with the small molecule class I PI3K inhibitor PI103, which exhibits activity against the PI3K isoforms p110α, p110b, p110γ, and p110δ ( Figure 4B). 24,25 MM.1S cells, which display strong constitutive activation of the PI3K/Akt pathway, were transfected with either pSUPER (mock control) or with pSUPER/PI3Kp110α, purified, and harvested 5 days after electroporation for western blotting ( Figure 4A).…”

PI3K inhibitor LY294002 inhibits activation of the Akt/mTOR pathway induced by an oncolytic adenovirus expressing TRAIL and sensitizes multiple myeloma cells to the oncolytic virus

“…We found that ZD55-TRAIL activated AKT and mTOR as evidenced by the upregulation of phosphor-mTOR (Ser2448) and phosphorylated AKT at Ser473 (Fig. 4A), which may stimulate MM cell growth and promote cell survival and migration (21,22). To improve the anti-myeloma efficacy of …”