Expression of α 6 integrin, a laminin receptor, on tumor cell surfaces is associated with reduced patient survival and increased metastasis in a variety of tumors. In prostate cancer, tumor extracapsular escape occurs in part via laminin-coated nerves and vascular dissemination, resulting in clinically significant bone metastases. We previously identified a novel form of α 6 integrin, called α 6 p, generated by urokinase-type plasminogen activator-dependent cleavage of the lamininbinding domain from the tumor cell surface. Cleavage increased laminin-dependent migration. Currently, we used the known conformation sensitivity of integrin function to determine if engagement of the extracellular domain inhibited integrin cleavage and the extravasation step of metastasis. We show that α 6 integrin was present on prostate carcinoma escaping the gland via nerves. Both endogenous and inducible levels of α 6 p were inhibited by engaging the extracellular domain of α 6 with monoclonal antibody J8H. J8H inhibited tumor cell invasion through Matrigel. A severe combined immunodeficient mouse model of extravasation and bone metastasis produced detectable, progressive osteolytic lesions within 3 weeks of intracardiac injections. Injection of tumor cells, pretreated with J8H, delayed the appearance of metastases. Validation of the α 6 cleavage effect on extravasation was confirmed through a genetic approach using tumor cells transfected with uncleavable α 6 integrin. Uncleavable α 6 integrin significantly delayed the onset and progression of osseous metastases out to six weeks post-injection. The results suggest that α 6 integrin cleavage permits extravasation of human prostate cancer cells from circulation to bone and can be manipulated to prevent metastasis.

T1736 is a novel phosphorylation site on the integrin β4 subunit that is phosphorylated downstream of protein kinase C and EGF receptor activation and is a substrate for protein kinase D1 in vitro and in cells. It contributes to the regulation of HD dynamics through modulating the association of β4 with plectin.

Chimeric antigen receptor (CAR) T-cell therapy is a promising treatment for patients with CD19+ B-cell malignancies. Combination strategies that improve CAR T-cell potency, limit tumor environment–mediated immune dysfunction, and directly reduce tumor burden may increase the potential for durable clinical benefit of CAR T-cell therapy. Lisocabtagene maraleucel (liso-cel) is a product therapy candidate being tested in patients with relapsed/refractory non-Hodgkin lymphoma or chronic lymphocytic leukemia. This study assessed the in vitro and in vivo functionality of CAR T cells transduced to express the anti-CD19 CAR of liso-cel in combination with ibrutinib or acalabrutinib. In prolonged stimulation assays, the presence of ibrutinib or acalabrutinib improved the CAR T-cell effector function. RNA-Seq analysis and surface marker profiling of these CAR T cells treated with ibrutinib but not acalabrutinib revealed gene expression changes consistent with skewing toward a memory-like, type 1 T-helper, Bruton tyrosine kinase phenotype. Ibrutinib or acalabrutinib improved CD19+ tumor clearance and prolonged survival of tumor-bearing mice when used in combination with CAR T cells. A combination of the defined cell product therapy candidate, liso-cel, with ibrutinib or acalabrutinib is an attractive approach that may potentiate the promising clinical responses already achieved in CD19+ B-cell malignancies with each of these single agents.

Anti-B-cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T cells have shown promising clinical responses in patients with relapsed/refractory multiple myeloma. Lenalidomide, an immunomodulatory drug, potentiates T cell functionality, drives antimyeloma activity, and alters the suppressive microenvironment; these properties may effectively combine with anti-BCMA CAR T cells to enhance function. Using an anti-BCMA CAR T, we demonstrated that lenalidomide enhances CAR T cell function in a concentration-dependent manner. Lenalidomide increased CAR T effector cytokine production, particularly under low CAR stimulation or in the presence of inhibitory ligand programmed cell death 1 ligand 1. Notably, lenalidomide also enhanced CAR T cytokine production, cytolytic activity, and activation profile relative to untreated CAR T cells in chronic stimulation assays. This unique potentiation of both short-term CAR T activity and long-term functionality during chronic stimulation prompted investigation of the molecular profile of lenalidomide-treated CAR T cells. Signatures from RNA sequencing and assay for transposase-accessible chromatin using sequencing indicated that pathways associated with T-helper 1 response, cytokine production, T cell activation, cell-cycle control, and cytoskeletal remodeling were altered with lenalidomide. Finally, study of lenalidomide and anti-BCMA CAR T cells in a murine, disseminated, multiple myeloma model indicated that lenalidomide increased CAR T cell counts in blood and significantly prolonged animal survival. In summary, preclinical studies demonstrated that lenalidomide potentiated CAR T activity in vivo in low-antigen or suppressive environments and delayed onset of functional exhaustion. These results support further investigation of lenalidomide and anti-BCMA CAR T cells in the clinic.

We describe the discovery of three structurally differentiated potent and selective MTH1 inhibitors and their subsequent use to investigate MTH1 as an oncology target, culminating in target (in)­validation. Tetrahydronaphthyridine 5 was rapidly identified as a highly potent MTH1 inhibitor (IC50 = 0.043 nM). Cocrystallization of 5 with MTH1 revealed the ligand in a Φ-cis-N-(pyridin-2-yl)­acetamide conformation enabling a key intramolecular hydrogen bond and polar interactions with residues Gly34 and Asp120. Modification of literature compound TH287 with O- and N-linked aryl and alkyl aryl substituents led to the discovery of potent pyrimidine-2,4,6-triamine 25 (IC50 = 0.49 nM). Triazolopyridine 32 emerged as a highly selective lead compound with a suitable in vitro profile and desirable pharmacokinetic properties in rat. Elucidation of the DNA damage response, cell viability, and intracellular concentrations of oxo-NTPs (oxidized nucleoside triphosphates) as a function of MTH1 knockdown and/or small molecule inhibition was studied. Based on our findings, we were unable to provide evidence to further pursue MTH1 as an oncology target.