Targeting CXCR4 with cell-penetrating pepducins in lymphoma and lymphocytic leukemia

Abstract

The chemokine receptor CXCR4, which normally regulates stromal stem cell interactions in the bone marrow, is highly expressed on a variety of malignant hematologic cells, including lymphoma and lymphocytic leukemias. A new treatment concept has arisen wherein CXCR4 may be an effective therapeutic target as an adjunct to treatment of hematologic neoplasms with chemo-and immunotherapy. In the present study, we developed pepducins, cell-penetrating lipopeptide antagonists of CXCR4, to interdict CXCL12-CXCR4 transmembrane signaling to intracellular G-proteins. We demonstrate that pepducins targeting the first (i1) or third (i3) intracellular loops of CXCR4 completely abrogate CXCL12-mediated cell migration of lymphocytic leukemias and lymphomas. Stromal-cell coculture protects lymphoma cells from apoptosis in response to treatment with the CD20-targeted Ab rituximab. However, combination treatment with CXCR4 pepducins and rituximab significantly increases the apoptotic effect of rituximab. Furthermore, treatment of mice bearing disseminated lymphoma xenografts with pepducins alone or in combination with rituximab significantly increased their survival. These data demonstrate that CXCL12-CXCR4 signaling can be effectively inhibited by cell-penetrating pepducins, which represents a potential new treatment strategy for lymphoid malignancies. (Blood. 2012;119(7):1717-1725) IntroductionHematologic malignancies account for almost 10% of new cancer cases in the United States each year. 1 The last decade has seen the introduction of rituximab, a humanized mAb directed against the CD20 Ag, as a treatment option for B-cell leukemia and lymphomas, and combination chemotherapy with rituximab is now standard treatment for aggressive non-Hodgkin lymphoma (NHL). 2 However, because approximately 60% of patients with aggressive NHL are not cured, new biologic therapies and targets are urgently needed to further improve overall survival.The chemokine G-protein-coupled receptor (GPCR) CXCR4 and its ligand, CXCL12 (also called stromal cell-derived factor-1␣ [SDF-1]), regulate a diverse array of cellular processes, including leukocyte trafficking, B-cell lymphopoiesis, and bone marrow myelopoiesis 3 ; survival and proliferation of hematopoietic stem cells (HSCs) 4 ; and homing of HSCs to the BM. Under normal physiologic conditions, HSCs and hematopoietic progenitor cells (HPCs) are predominantly present in the BM, where they give rise to the mature cells of the hematopoietic system that are released into the blood circulation. 5 CXCL12 is constitutively secreted at high levels by BM stromal cells, 6 and it is this chemokine gradient that retains HSCs and HPCs in the BM and regulates homing of CXCR4-expressing cells. 7 The small-molecule antagonist plerixafor (AMD3100), which targets the CXCR4/CXCL12-SDF1 signaling axis, is an effective clinical tool with which to enhance mobilization of HSCs to the peripheral blood for subsequent autologous transplantation, 8,9 and has recently been approved for use in combination with G-CSF as a stem c...

Targeting the CD20 and CXCR4 Pathways in Non-Hodgkin Lymphoma with Rituximab and High-Affinity CXCR4 Antagonist BKT140

“…Moreover, antagonizing CXCR4 and CXCL12 significantly inhibited the growth of Epstein-Bar virus (EBV)-transformed B cells injected intraperitoneally into NOD/SCID mice and prolonged animal survival (39). Furthermore, recently published study has shown the efficacy of cell-penetrating lipopeptide CXCR4 antagonists, called pepducins, to enhance rituximab-induced apoptosis of lymphoma cells in vitro and in vivo (40).…”

Pepducin targeting the C-X-C chemokine receptor type 4 acts as a biased agonist favoring activation of the inhibitory G protein

“…Although the precise mode of action is not completely understood, it is believed that pepducins bind to their target receptors and allosterically modulate their signaling activity (2,3). Pepducins have been identified for several GPCRs, including the proteaseactivated receptors PAR1 (1,(4)(5)(6)(7)(8)(9)(10), PAR2 (1,(11)(12)(13), and PAR4 (6,9), the formyl peptide receptor-2 (14), the melanocortin type 4 receptor (1), the sphingosine 1-phosphate receptor 3 (15), and the C-X-C chemokine receptor type 1, 2 (CXCR1, CXCR2) (16), and 4 (CXCR4) (2,17,18). They have been found to act as allosteric agonists as well as negative or positive allosteric modulators.…”

Prospects for use of peptides and their derivatives, structurally corresponding to the G protein-coupled receptors, in medicine

“…Вследствие этого, селективные CXCR4-антагонисты, в том числе созданные на основе пепдуцинов, представляют большой интерес как противораковые препараты, действие которых основано на прерывании сигналов, генерируемых активацией рецептора CXCR4 [17,32]. Обнаружено, что пепдуцины, производные ЦП-1 и ЦП-3 рецептора CXCR4, полностью блокируют опосредуемую этим рецептором миграцию клеток лимфоцитарного лейкоза и лимфомы [33]. Несмотря на то, что проапоптотическое действие ретуксимаба, моноклональных антител к CD20-антигену, который экспрессируется в B-клетках лимфомы, полностью блокировалось обработкой этих клеток стромальным фактором CXCL12/SDF-1, при совместном действии ретуксимаба и CXCR4-пепдуцинов их проапоптотический эффект в присутствии фактора CXCL12/SDF-1 сохранялся.…”

“…Несмотря на то, что проапоптотическое действие ретуксимаба, моноклональных антител к CD20-антигену, который экспрессируется в B-клетках лимфомы, полностью блокировалось обработкой этих клеток стромальным фактором CXCL12/SDF-1, при совместном действии ретуксимаба и CXCR4-пепдуцинов их проапоптотический эффект в присутствии фактора CXCL12/SDF-1 сохранялся. Пепдуцины как при монотерапии, так и в сочетании с ретуксимабом, также эффективно подавляли развитие и метастазирование трансплантантов лимфомы и лимфоцитарного лейкоза [33].…”