Ilyas Sahin

C1013G/CXCR4 acts as a driver mutation of tumor progression and modulator of drug resistance in lymphoplasmacytic lymphoma

The C-X-C chemokine receptor type 4 (CXCR4) plays a crucial role in modulating cell trafficking in hematopoietic stem cells and clonal B cells. We screened 418 patients with B-cell lymphoproliferative disorders and described the presence of the C1013G/CXCR4 warts, hypogammaglobulinemia, infections, and myelokathexis-associated mutation in 28.2% (37/131) of patients with lymphoplasmacytic lymphoma (Waldenström macroglobulinemia [WM]), being either absent or present in only 7% of other B-cell lymphomas. In vivo functional characterization demonstrates its activating role in WM cells, as demonstrated by significant tumor proliferation and dissemination to extramedullary organs, leading to disease progression and decreased survival. The use of a monoclonal antibody anti-CXCR4 led to significant tumor reduction in a C1013G/CXCR4 WM model, whereas drug resistance was observed in mutated WM cells exposed to Brutons tyrosine kinase, mammalian target of rapamycin, and phosphatidylinositol 3-kinase inhibitors, but not proteasome inhibitors. These findings demonstrate that C1013G/CXCR4 is an activating mutation in WM and support its role as a critical regulator of WM molecular pathogenesis and as an important therapeutic target.

The sialyltransferase ST3GAL6 influences homing and survival in multiple myeloma

Glycosylation is a stepwise procedure of covalent attachment of oligosaccharide chains to proteins or lipids, and alterations in this process, especially increased sialylation, have been associated with malignant transformation and metastasis. The role of altered sialylation in multiple myeloma (MM) cell trafficking has not been previously investigated. In the present study we identified high expression of β-galactoside α-2,3-sialyltransferase, ST3GAL6, in MM cell lines and patients. This gene plays a key role in selectin ligand synthesis in humans through the generation of functional sialyl Lewis X. In MRC IX patients, high expression of this gene is associated with inferior overall survival. In this study we demonstrate that knockdown of ST3GAL6 results in a significant reduction in levels of α-2,3-linked sialic acid on the surface of MM cells with an associated significant reduction in adhesion to MM bone marrow stromal cells and fibronectin along with reduced transendothelial migration in vitro. In support of our in vitro findings, we demonstrate significantly reduced homing and engraftment of ST3GAL6 knockdown MM cells to the bone marrow niche in vivo, along with decreased tumor burden and prolonged survival. This study points to the importance of altered glycosylation, particularly sialylation, in MM cell adhesion and migration.

CXCR4 regulates extra-medullary myeloma through epithelial-mesenchymal transition-like transcriptional activation

Extra-medullary disease (EMD) in multiple myeloma (MM) is associated with poor prognosis and resistance to chemotherapy. However, molecular alterations that lead to EMD have not been well defined. We developed bone marrow (BM)- and EMD-prone MM syngeneic cell lines; identified that epithelial-to-mesenchymal transition (EMT) transcriptional patterns were significantly enriched in both clones compared to parental cells, together with higher levels of CXCR4 protein; and demonstrated that CXCR4 enhanced the acquisition of an EMT-like phenotype in MM cells with a phenotypic conversion for invasion, leading to higher bone metastasis and EMD dissemination in vivo. In contrast, CXCR4 silencing led to inhibited tumor growth and reduced survival. Ulocuplumab, a monoclonal anti-CXCR4 antibody, inhibited MM cell dissemination, supported by suppression of the CXCR4-driven EMT-like phenotype. These results suggest that targeting CXCR4 may act as a regulator of EMD through EMT-like transcriptional modulation, thus representing a potential therapeutic strategy to prevent MM disease progression.

Pyk2 promotes tumor progression in multiple myeloma.

Proline-rich tyrosine kinase 2 (Pyk2) is a member of the focal adhesion kinase family that has been recently linked to tumor development. However, its role in modulating multiple myeloma (MM) biology and disease progression remains unexplored. We first demonstrated that patients with MM present with higher expression of Pyk2 compared with healthy individuals. By using loss-of-function approaches, we found that Pyk2 inhibition led to reduction of MM tumor growth in vivo as well as decreased cell proliferation, cell-cycle progression, and adhesion ability in vitro. In turn, overexpression of Pyk2 promoted the malignant phenotype, substantiated by enhanced tumor growth and reduced survival. Mechanistically, inhibition of Pyk2 reduced activation of Wnt/β-catenin signaling by destabilizing β-catenin, leading to downregulation of c-Myc and Cyclin D1. Furthermore, treatment of MM cells with the FAK/Pyk2 inhibitor VS-4718 effectively inhibited MM cell growth both in vitro and in vivo. Collectively, our findings describe the tumor-promoting role of Pyk2 in MM, thus providing molecular evidence for a novel tyrosine kinase inhibitor as a new therapeutic option in MM.

Targeting vasculogenesis to prevent progression in multiple myeloma

The role of endothelial progenitor cell (EPC)-mediated vasculogenesis in hematological malignancies is not well explored. Here, we showed that EPCs are mobilized from the bone marrow (BM) to the peripheral blood at early stages of multiple myeloma (MM); and recruited to MM cell-colonized BM niches. Using EPC-defective ID1+/− ID3−/− mice, we found that MM tumor progression is dependent on EPC trafficking. By performing RNA-sequencing studies, we confirmed that endothelial cells can enhance proliferation and favor cell-cycle progression only in MM clones that are smoldering-like and have dependency on endothelial cells for tumor growth. We further confirmed that angiogenic dependency occurs early and not late during tumor progression in MM. By using a VEGFR2 antibody with anti-vasculogenic activity, we demonstrated that early targeting of EPCs delays tumor progression, while using the same agent at late stages of tumor progression is ineffective. Thus, although there is significant angiogenesis in myeloma, the dependency of the tumor cells on EPCs and vasculogenesis may actually precede this step. Manipulating vasculogenesis at an early stage of disease may be examined in clinical trials in patients with smoldering MM, and other hematological malignancies with precursor conditions.

Drug Delivery Approaches for the Treatment of Cervical Cancer.

Cervical cancer is a highly prevalent cancer that affects women around the world. With the availability of new technologies, researchers have increased their efforts to develop new drug delivery systems in cervical cancer chemotherapy. In this review, we summarized some of the recent research in systematic and localized drug delivery systems and compared the advantages and disadvantages of these methods.

Waldenström macroglobulinemia: from biology to treatment

Waldenström macroglobulinemia (WM) is distinct B-cell lymphoproliferative disorder primarily characterized by bone marrow infiltration of lymphoplasmacytic cells along with production of a serum monoclonal (IgM). In this review, we describe the biology of WM, the diagnostic evaluation for WM with a discussion of other conditions that are in the differential diagnosis and clinical manifestations of the disease as well as current treatment options. Within the novel agents discussed are everolimus, perifosine, enzastaurin, panobinostat, bortezomib and carfilzomib, pomalidomide and ibrutinib. Many of the novel agents have shown good responses and have a better toxicity profile compared to traditional chemotherapeutic agents, which makes them good candidates to be used as primary therapies for WM in the future.

Targeting survival and cell trafficking in multiple myeloma and Waldenstrom macroglobulinemia using pan‐class I PI3K inhibitor, buparlisib

The phosphatidylinositol‐3 kinase (PI3K) pathway is activated in multiple myeloma (MM) and Waldenstrom Macroglobulenima (WM), and plays a crucial role in tumor progression and drug resistance. In this study, we characterized the role of pan‐class I PI3K inhibition on cell trafficking and survival of MM and WM cells. We tested the effect of pan‐class I PI3K inhibition by siRNA silencing or pharmacologic inhibition with buparlisib on MM cell survival, apoptosis and cell cycle in vitro and tumor growth and mobilization of MM cells in vivo. We then evaluated buparlisib‐dependent mechanisms of induced MM cell mobilization. Moreover, the effect of buparlisib on cell survival, apoptosis, and adhesion of WM cells to bone marrow stromal cells (BMSCs) has been evaluated. We showed that buparlisib induced toxicity in MM cells, supported by induction of apoptosis and cell cycle arrest. Buparlisib was also found to reduce tumor progression in vivo. Importantly, buparlisib enhanced MM cell mobilization in vivo which was driven by decreased adhesion of MM cells to BMSCs and increased chemotaxis via up‐regulation of CXCR4 expression. Similar to its effects on MM cells, buparlisib also induced cell survival and apoptosis, and decreased adhesion in WM cells. These data highlight the critical contribution of class I PI3K signaling to the regulation of survival and cell dissemination in B‐cell malignancies. Am. J. Hematol. 89:1030–1036, 2014.

The influence of hypoxia on CML trafficking through modulation of CXCR4 and E-cadherin expression

The influence of hypoxia on CML trafficking through modulation of CXCR4 and E-cadherin expression

Distinct roles of class I PI3K isoforms in multiple myeloma cell survival and dissemination.

Distinct roles of class I PI3K isoforms in multiple myeloma cell survival and dissemination