Background: C-type lectins play important roles in immunity and homeostasis.Results: CLECSF8 is expressed on neutrophils and monocytes and can mediate phagocytosis, the respiratory burst and inflammatory cytokine production, in part through association with a novel adaptor.Conclusion: CLECSF8 can trigger cellular activation.Significance: This study identifies a novel C-type lectin that can control immune cell function.

Historically, drugs used in the treatment of cancers also tend to cause damage to healthy cells while affecting cancer cells. Therefore, the identification of novel agents that act specifically against cancer cells remains a high priority in the search for new therapies. In contrast to normal cells, most cancer cells contain multiple centrosomes which are associated with genome instability and tumorigenesis. Cancer cells can avoid multipolar mitosis, which can cause cell death, by clustering the extra centrosomes into two spindle poles, thereby enabling bipolar division. Kinesin-like protein KIFC1 plays a critical role in centrosome clustering in cancer cells, but is not essential for normal cells. Therefore, targeting KIFC1 may provide novel insight into selectively killing of cancer cells. In the present study, we identified a small molecule KIFC1 inhibitor, SR31527, which inhibited microtubule-stimulated KIFC1 ATPase activity with an IC50 value of 6.6 μM. By using bio-layer interferometry technology, we further demonstrated that SR31527 bound directly to KIFC1 with high affinity (Kd = 25.4 nM). Our results from computational modeling and STD-NMR experiment suggested that SR31527 bound to a novel allosteric site of KIFC1 that appears suitable for developing selective inhibitors of KIFC1. Importantly, SR31527 prevented bipolar clustering of extra-centrosomes in triple negative breast cancer (TNBC) cells and significantly reduced TNBC cell colony formation and viability, but was less toxic to normal fibroblasts. Therefore, SR31527 provides a valuable tool for studying the biological function of KIFC1 and serves as a potential lead for the development of novel therapeutic agents for breast cancer treatment.

Background: LRRK2 kinase activity is linked to neurodegeneration. Results: Novel small molecule inhibitors provide insight into the structure and function of the LRRK2 kinase domain. Conclusion: A unique ATP-binding pocket structure in LRRK2 allows for potent and specific activity-selective and mutantselective small molecules. Significance: Novel structure-activity relationships can be exploited for the development of new classes of kinase inhibitors.

TGF-β has been a target of interest for the treatment of fibrotic diseases and certain cancers. Approaches to target TGF-β include antagonists of the active ligand or TGF-β receptor kinase activity. These approaches have failed in clinical trials due to a lack of effectiveness and a limited therapeutic window. In this context, newer and more selective approaches to target TGF-β are needed. We previously reported that the matricellular protein, thrombospondin 1, activates the latent TGF-β complex and that antagonism of this pathway using tri/tetrapeptides in various animal models reduces fibrosis. The tripeptide, SRI-31277 (1), is effective in vivo but has a short plasma half life (0.2 h). Herein we describe the design and synthesis SRI-31277 analogs, specifically smaller peptides that retain potency and have improved bioavailability. We identified SRI-35241 (36) with a single chiral center, which blocks TGF-β activation (pIC 50 = 8.12 nM) and has a plasma half life of 1.8 h (iv).

HIV-1 Vpu targets the host cell proteins CD4 and BST-2/Tetherin for degradation, ultimately resulting in enhanced virus spread and host immune evasion. The discovery and characterization of small molecules that antagonize Vpu would further elucidate the contribution of Vpu to pathogenesis and lay the foundation for the study of a new class of novel HIV-1 therapeutics. To identify novel compounds that block Vpu activity, we have developed a cell-based ‘gain of function’ assay that produces a positive signal in response to Vpu inhibition. To develop this assay, we took advantage of the viral glycoprotein, GaLV Env. In the presence of Vpu, GaLV Env is not incorporated into viral particles, resulting in non-infectious virions. Vpu inhibition restores infectious particle production. Using this assay, a high throughput screen of >650,000 compounds was performed to identify inhibitors that block the biological activity of Vpu. From this screen, we identified several positive hits but focused on two compounds from one structural family, SRI-41897 and SRI-42371. We developed independent counter-screens for off target interactions of the compounds and found no off target interactions. Additionally, these compounds block Vpu-mediated modulation of CD4, BST-2/Tetherin and antibody dependent cell-mediated toxicity (ADCC). Unfortunately, both SRI-41897 and SRI-42371 were shown to be specific to the N-terminal region of NL4-3 Vpu and did not function against other, more clinically relevant, strains of Vpu; however, this assay may be slightly modified to include more significant Vpu strains in the future.

HIV-1 Vpu targets the host cell proteins CD4 and BST-2/Tetherin for degradation, ultimately resulting in enhanced virus spread and host immune evasion. The discovery and characterization of small molecules that antagonize Vpu would further elucidate the contribution of Vpu to pathogenesis and lay the foundation for the study of a new class of novel HIV-1 therapeutics. To identify novel compounds that block Vpu activity, we developed a cell-based 'gain of function' assay that produces a positive signal in response to Vpu inhibition. To develop this assay, we took advantage of the viral glycoprotein, GaLV Env. In the presence of Vpu, GaLV Env is not incorporated into viral particles, resulting in non-infectious virions. Vpu inhibition restores infectious particle production. Using this assay, a high throughput screen of >650,000 compounds was performed to identify inhibitors that block the biological activity of Vpu. From this screen, we identified several positive hits but focused on two compounds from one structural family, SRI-41897 and SRI-42371. It was conceivable that the compounds inhibited the formation of infectious virions by targeting host cell proteins instead of Vpu directly, so we developed independent counter-screens for off target interactions of the compounds and found no off target interactions. Additionally, these compounds block Vpu-mediated modulation of CD4, BST-2/Tetherin and antibody dependent cell-mediated toxicity (ADCC). Unfortunately, both SRI-41897 and SRI-42371 were shown to be specific to the N-terminal region of NL4-3 Vpu and did not function against other, more clinically relevant, strains of Vpu.

Historically, drugs used in the treatment of certain cancers may cause damage to healthy cells while affecting cancer cells. Therefore, finding compounds that are specific toward cancer cells only is still a high priority in the search for new therapies. In contrast with normal cells, most cancer cells contain multiple centrosomes which are associated with genome instability and tumorigenesis. Cancer cells can avoid multipolar mitosis which can cause cell death by clustering the extra centrosomes into two spindle poles, thereby enabling bipolar division. Kinesin-like protein KIFC1 plays a critical role in centrosome clustering in cancer cells, but is not essential for normal cell survival. Therefore, targeting KIFC1 may give some insight into how a novel therapy can selectively target only cancer cells. Here, we report that KIFC1 up-regulation is a frequent event in human breast cancer and that KIFC1 is highly expressed in all 8 tested human breast cancer cell lines, but is absent in normal human mammary epithelial cells and weakly expressed in 2 human lung fibroblast lines. We also found that depletion of KIFC1 in breast cancer cells induced cell death. From a high throughput screen of 30,000 compounds, we identified a small molecule KIFC1 inhibitor, SRH06, which has an enzymatic IC50 value of 6.5 μM versus KIFC1 and binds directly to KIFC1 without interacting with the microtubule. Results from our computer modeling studies suggested that SRH06 binds to a novel allosteric site on KIFC1 that appears suitable for the development of selective KIFC1 inhibitors. Importantly, SRH06 prevented bipolar clustering of extra-centrosomes in breast cancer cells and significantly reduced colony formation and cell viability, but was less toxic to normal LL47 fibroblasts. Therefore, SRH06 provides a very valuable tool to study the biological function of KIFC1 and serves as a potential lead for the development of a novel therapeutic agent for the treatment of breast cancer. Citation Format: Wei Zhang, Ling Zhai, Wenyan Lu, Yimin Wang, Vandana V. Gupta, Indira Padmalayam, Robert J. Bostwick, Lucile White, Ross Larry, Joseph Maddry, Sam Ananthan, Mark Suto, Bo Xu, Rongbao Li, Yonghe Li. Discovery and evaluation of a small molecule KIFC1 inhibitor for breast cancer treatment. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1746. doi:10.1158/1538-7445.AM2015-1746

Background: Current established methods of circulating tumor cell (CTC) isolation and identification rely on antibodies against epithelial specific markers such as epithelial cell adhesion molecule (EpCAM) and cytokeratin (CK). The classical phenotypic definition of a CTC is a CK positive, CD45 negative, nucleated cell, yet several reports have shown that EpCAM and CK detect only a fraction of CTCs and are not sufficient to detect the heterogeneous subpopulations of CTCs. Moreover, subsets of primary tumor cells acquire features of invasiveness and transform into an aggressive phenotype. During this process, EpCAM and CK are down regulated or lost leaving a lethal population of CTCs undetectable and unstudied using antibody dependent CTC technologies. It is imperative to isolate CTCs in an unbiased, EpCAM independent manner and expand the phenotypic characterization of CTCs to elucidate the subpopulation heterogeneity. Here we used ApoStream™, a novel, antibody-independent device which exploits differences in the dielectric properties between cancer cells and normal blood cells to enrich CTCs from the blood of cancer patients. We demonstrate device performance and integration with additional methods to perform subsequent phenotyping and molecular marker analysis. Methods: The performance of ApoStream™ was assessed using SKOV3 (ovarian cancer) and MDA-MB-231 (breast cancer) cell lines that have a high and low expression level of EpCAM, respectively, to demonstrate linearity and precision of recovery independent of EpCAM receptor levels. A side-by-side comparison of CellSearch® and ApoStream™ was performed on 10 metastatic breast cancer patients. A multiplexed immunofluorescent assay and laser scanning cytometry (LSC) analyses were applied to identify multiple combinations of positive and/or negative staining for CK/CD45/DAPI cells, expression of EpCAM and vimentin. Results: In system precision performance studies, the average recovery of SKOV3 and MDA-MB-231 cancer cells spiked into approximately 12 million peripheral blood mononuclear cells obtained from 7.5 mL normal donor blood was 75.4 ± 3.1% (n = 12) and 71.2 ± 1.6% (n = 6), respectively. The intra-day and inter-day precision coefficients of variation (CVs) of the device were both less than 3%. Linear regression analysis yielded a correlation coefficient (R2) of more than 0.99 for a spiking range of 4-2600 cells. ApoStream™ consistently recovered significantly higher numbers of CTCs compared to CellSearch® (p = 0.024). ApoStream™ recovered varying numbers of CK+/CD45−/DAPI+, CK+/CD45+/DAPI+, CK−/CD45−/DAPI+ cells from each cancer patient sample tested. ApoStream™ recovered both EpCAM+ and EpCAM− CTCs in 50% and 90% of patients, respectively. Vimentin+ CTCs were isolated from 90% of patients. Conclusions: The ApoStream™ technology circumvents dependence on expression of EpCAM and recovers CTCs in high percentage of patients. ApoStream™ coupled with LSC analysis is a sensitive method for phenotyping and detecting biomarker expression in CTCs. These results demonstrate the broad applicability of ApoStream™ for enrichment and molecular characterization of CTCs as a foundation for improved clinical applications of CTCs. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-04-05.