A small molecule inhibitor of alpha4 integrin-dependent cell migration

Novel Ligands Targeting α4β1 Integrin: Therapeutic Applications and Perspectives

Among the other members of the adhesion molecules' family, α4β1 integrin, a heterodimeric receptor, plays a crucial role in inflammatory diseases, cancer development, metastasis and stem cell mobilization or retention. In many cases, its function in pathogenesis is not yet completely understood and investigations on ligand binding and related stabilization of active/inactive conformations still represent an important goal. For this reason, starting from the highlight of α4β1 functions in human pathologies, we report an overview of synthetic α4β1 integrin ligands under development as potential therapeutic agents. The small molecule library that we have selected represents a collection of lead compounds. These molecules are the object of future refinement in academic and industrial research, in order to achieve a fine tuning of α4β1 integrin regulation for the development of novel agents against pathologies still eluding an effective solution.

Integrins as therapeutic targets in the organ-specific metastasis of human malignant melanoma

Integrins are a large family of adhesion molecules that mediate cell-cell and cell-extracellular matrix interactions. Among the 24 integrin isoforms, many have been found to be associated with tumor angiogenesis, tumor cell migration and proliferation, and metastasis. Integrins, especially αvβ3, αvβ5 and α5β1, participate in mediating tumor angiogenesis by interacting with the vascular endothelial growth factor and angiopoietin-Tie signaling pathways. Melanoma patients have a poor prognosis when the primary tumor has generated distant metastases, and the melanoma metastatic site is an independent predictor of the survival of these patients. Different integrins on the melanoma cell surface preferentially direct circulating melanoma cells to different organs and promote the development of metastases at specific organ sites. For instance, melanoma cells expressing integrin β3 tend to metastasize to the lungs, whereas those expressing integrin β1 preferentially generate lymph node metastases. Moreover, tumor cell-derived exosomes which contain different integrins may prepare a pre-metastatic niche in specific organs and promote organ-specific metastases. Because of the important role that integrins play in tumor angiogenesis and metastasis, they have become promising targets for the treatment of advanced cancer. In this paper, we review the integrin isoforms responsible for angiogenesis and organ-specific metastasis in malignant melanoma and the inhibitors that have been considered for the future treatment of metastatic disease.

Antitumor effect of the integrin α4 signaling inhibitor JK273 in non-small cell lung cancer NCI-H460 cells

Lung cancer accounts for the highest death rate among cancers worldwide, with most patients being diagnosed with non-small cell lung cancer (NSCLC), urging more effective therapies. We report that JK273, a pyrrolo[2,3-d]pyrimidine analog, which inhibits α4 integrin signaling, showed a selective cytotoxic effect against HCI-H460 NSCLC cells, with an IC₅₀ of 0.98 ± 0.15 μM, but showed less sensitivity to fibroblasts with a selectivity index (SI) greater than 30. This effect was attributed to cell cycle arrest at S phase by JK273 treatment, resulting in the apoptosis of NCI-H460 cells, further confirmed by exposing phosphatidylserine and morphological changes. Taken together with the previous study of JK273 inhibiting cell migration, we propose that JK273 could serve as an antitumor compound to specifically target cancer cells but not non-cancerous cells by triggering programmed cell death, in addition to anti-metastatic effects in cancer therapy.

Phenotypic screening in cancer drug discovery - past, present and future

There has been a resurgence of interest in the use of phenotypic screens in drug discovery as an alternative to target-focused approaches. Given that oncology is currently the most active therapeutic area, and also one in which target-focused approaches have been particularly prominent in the past two decades, we investigated the contribution of phenotypic assays to oncology drug discovery by analysing the origins of all new small-molecule cancer drugs approved by the US Food and Drug Administration (FDA) over the past 15 years and those currently in clinical development. Although the majority of these drugs originated from target-based discovery, we identified a significant number whose discovery depended on phenotypic screening approaches. We postulate that the contribution of phenotypic screening to cancer drug discovery has been hampered by a reliance on 'classical' nonspecific drug effects such as cytotoxicity and mitotic arrest, exacerbated by a paucity of mechanistically defined cellular models for therapeutically translatable cancer phenotypes. However, technical and biological advances that enable such mechanistically informed phenotypic models have the potential to empower phenotypic drug discovery in oncology.

4-Methyl-3-nitro-benzoic acid, a migration inhibitor, prevents breast cancer metastasis in SCID mice

Metastasis remains a formidable problem in malignant tumors. In this study, MTT assay revealed that 4-methyl-3-nitro-benzoic acid (MNBA) had no effect on cell viability and did not interfere with cell cycle in any breast cancer cell lines tested. However, treatment with MNBA on breast cancer cells can inhibit EGF-induced migration and chemotaxis in vitro. In vivo assay demonstrated that MNBA and Paclitaxel synergistically inhibited tumor growth and metastasis in breast cancer SCID mice xenografts. These results suggest that MNBA is a potent inhibitor cancer cell chemotaxis and may be developed into a novel anti-metastasis drug.

Abl-interactor-1 (Abi1) has a role in cardiovascular and placental development and is a binding partner of the alpha4 integrin

Dynamic signals linking the actin cytoskeleton and cell adhesion receptors are essential for morphogenesis during development and normal tissue homeostasis. Abi1 is a central regulator of actin polymerization through interactions with multiple protein complexes. However, the in vivo role of Abi1 remains to be defined. The α4 integrin adhesion receptor is associated with enhanced protrusive activity and regulation of directional cell migration. Among integrin subunits, α4 exhibits unique properties in that it predominantly accumulates at the leading edge of migrating cells; however, the pathways that link the actin-regulatory machinery to α4 at the leading edge have remained elusive. We generated Abi1 KO mice and found that loss of Abi1 phenocopies KO of α4. Mice lacking Abi1 or α4 exhibit midgestational lethality with abnormalities in placental and cardiovascular development. Notably, purified Abi1 protein binds directly to the α4 cytoplasmic tail and endogenous Abi1 colocalizes with phosphorylated α4 at the leading edge of spreading cells. Moreover, Abi1-deficient cells expressing α4 have impaired cell spreading, which is rescued by WT Abi1 but not an Abi1 mutant lacking the α4-binding site. These data reveal a direct link between the α4 integrin and actin polymerization and uncover a role for Abi1 in the regulation of morphogenesis in vivo. The Abi1-α4 interaction establishes a mechanistic paradigm for signaling between adhesion events and enhanced actin polymerization at the earliest stages of protrusion.