Nacusi, Lucas P.

Abstract The NK cell activating receptor NKG2D plays a critical role in the destruction of malignant cells, but many of the cell-signaling mechanisms governing NKG2D-mediated cellular cytotoxicity are unknown. We have identified an NKG2D-mediated signaling pathway that governs both conjugate formation and cytotoxic granule polarization. We demonstrate that an interaction between the regulatory subunit of PI3K, p85, and the adaptor protein CrkL is required for efficient NKG2D-mediated cellular cytotoxicity. We show decreased NK cell - target cell conjugate formation in NK cells treated with PI3K inhibitors or depleted of CrkL. Independent of adhesion, we find that microtubule organization center polarization toward target cells expressing the NKG2D ligand MICA or toward anti-NKG2D coated beads is impaired in the absence of CrkL. Antibody-stimulated granule release is also impaired in NK cells depleted of CrkL. Furthermore, our data indicate that the small Ras-family GTPase Rap1 is required for NK cell killing and is activated downstream of NKG2D engagement in a PI3K- and CrkL-dependent manner. Taken together, our data identify an NKG2D-activated signaling pathway that collectively orchestrates NK cell adhesion, cell polarization and granule release.

Abstract Recent studies suggest that progression to castrate-resistant prostate cancer (CRPC) is due to generation of androgen receptor (AR) splice variants, lacking the ligand binding domain. These AR variants originally identified in cell-based models of CRPC, have also been detected in benign and malignant human prostate tissue, with the highest levels observed in late state CRPC. The diversity and complexity of AR variants is well appreciated but not fully understood. Using RT-PCR we assessed the expression of a number of AR variants in cell-based models of both castrate-resistant and androgen-dependent prostate cancer. Several AR variants were expressed in both 22Rv1 and VCaP cells, but not in LNCaP cells. Coding sequences for AR variants were cloned into expression vectors and constitutive transcriptional activity was observed using a luciferase reporter assay. Augmented transcriptional activity of AR variants was observed in cells that express full-length AR, when full-length AR was silenced using shRNA targeting exons 7/8. This observation suggests the constitutive activity of AR variants may be independent of full-length AR. We profiled the AR variant transcriptome in 22Rv1 cells, using the Illumina HumanHT12 v4 whole-genome expression array platform. shRNA targeting exon 1 was used to silence all AR isoforms and shRNA targeting exons 7/8 was used to silence full-length AR. 5,256 genes were modulated by knocking down all AR isoforms and 5,086 genes were modulated by knocking down full-length AR. A total of 3,714 genes were common to both groups, leaving 1542 genes modulated by AR variants and 1372 modulated by full-length AR (p<0.05). The represents a subset of genes differentially regulated by AR variants independently of full length AR. Aggregate function of multiple AR variants may confer a CRPC phenotype independent of full-length AR. Pathway analysis of these genes differentially regulated by AR variants may reveal potential targets for therapeutic intervention in patients who progress despite androgen deprivation or anti-androgen therapy. (Supported by NIH grants CA125747, CA091956 and CA121277, T.J. Martell Foundation and the Mayo Clinic Prostate Cancer SPORE). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2924. doi:1538-7445.AM2012-2924

Abstract Purpose. Prostate cancer (PCa) continues to be a leading cause of cancer death in males worldwide. In the prostate, androgens play a crucial role in both normal and cancerous growth by acting through the androgen receptor (AR), a member of the nuclear receptor super-family; hence, the AR has become a target of therapeutic intervention. The standard treatment for advanced PCa is androgen ablation therapy, initially leading to tumor regression through inhibition of AR activity. However, the success of androgen ablation therapy is often terminated by the emergence of castration- recurrent PCa (CRPC), for which there is still no cure. CRPC remains dependent on a functional AR-axis for proliferation and drugs targeting this network are continually being developed. We have examined the effects of Millennium-Takeda investigational compound T-1759243 on both androgen-responsive and androgen-refractory PCa cells in order to assess its therapeutic potential. Methods. We used PCa cell lines LNCaP, LNCaP-C42 and 22RV1 and assessed effects on cell viability and proliferation using MTS and BrdU assays. AR activity was measured using PSA-luciferase reporter constructs and protein levels by western blot. Microarray analysis with the Illumina HT-12 platform was used to identify genes affected by treatment with T-1759243, followed by real-time PCR confirmation. Pathway analysis was performed using MetaCoreTM software. Results. Our studies have revealed that T-1759243 reduces viability in all cell lines examined, regardless of androgen responsiveness. Treatment resulted in decreased proliferation in androgen-responsive cells and increased apoptosis in refractory cells. AR activity, as measured by PSA-luciferase assay, was greatly decreased in all cell lines by 10uM T-1759243 and T-1759243 abrogated the ability of synthetic androgen R1881 to increase AR activity by inhibiting nuclear translocation of the AR in refractory cells. Pathway analysis revealed changes in genes involved in cell-cycle, cell adhesion and cytoskeletal remodeling in addition to genes in androgen target pathways. Conclusions. T-1759243 is a novel AR antagonist that inhibits AR activity in both androgen-dependent and androgen-refractory prostate cancer cells. Additionally, it inhibits the ability of androgen to promote nuclear translocation of the AR and thus stimulate AR activity in castrate-resistant prostate cancer cells. Pathways affected by treatment with T-1759243 are cell-specific and dependent on AR status and may reveal novel gene targets in PCa treatment. This work was supported in part by Grant #35 from Millennium Pharmaceuticals, Inc the Takeda Oncology Company. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 940. doi:1538-7445.AM2012-940

Abstract The NK cell-activating receptor NKG2D plays a critical role in the destruction of malignant cells, but many of the cell-signaling mechanisms governing NKG2D-mediated cellular cytotoxicity are unknown. We have identified an NKG2D-mediated signaling pathway that governs both conjugate formation and cytotoxic granule polarization. We demonstrate that an interaction between the regulatory subunit of PI3K, p85, and the adaptor protein CrkL is required for efficient NKG2D-mediated cellular cytotoxicity. We show decreased NK cell-target cell conjugate formation in NK cells treated with PI3K inhibitors or depleted of CrkL. Independent of adhesion, we find that microtubule organization center polarization toward target cells expressing the NKG2D ligand MICA or toward anti-NKG2D-coated beads is impaired in the absence of CrkL. Ab-stimulated granule release is also impaired in NK cells depleted of CrkL. Furthermore, our data indicate that the small Ras family GTPase Rap1 is activated downstream of NKG2D engagement in a PI3K- and CrkL-dependent manner and is required for conjugate formation, MTOC (microtubule organizing center) polarization, and NKG2D-dependent cellular cytotoxicity. Taken together, our data identify an NKG2D-activated signaling pathway that collectively orchestrates NK cell adhesion, cell polarization, and granule release.

WAVE2 regulates T cell receptor (TCR)–stimulated actin cytoskeletal dynamics leading to both integrin clustering and affinity maturation. Although WAVE2 mediates integrin affinity maturation by recruiting vinculin and talin to the immunological synapse in an Arp2/3-dependent manner, the mechanism by which it regulates integrin clustering is unclear. We show that the Abl tyrosine kinase associates with the WAVE2 complex and TCR ligation induces WAVE2-dependent membrane recruitment of Abl. Furthermore, we show that WAVE2 regulates TCR-mediated activation of the integrin regulatory guanosine triphosphatase Rap1 via the recruitment and activation of the CrkL–C3G exchange complex. Moreover, we demonstrate that although Abl does not regulate the recruitment of CrkL–C3G into the membrane, it does affect the tyrosine phosphorylation of C3G, which is required for its guanine nucleotide exchange factor activity toward Rap1. This signaling node regulates not only TCR-stimulated integrin clustering but also affinity maturation. These findings identify a previously unknown mechanism by which the WAVE2 complex regulates TCR signaling to Rap1 and integrin activation.