Cancer-induced expansion and activation of CD11b+ Gr-1+ cells predispose mice to adenoviral-triggered anaphylactoid-type reactions.

Intravascular delivery (1.5 x 10(9) particles and higher) of recombinant adenovirus (rAd) induces myeloid cell mediated, self-limiting hemodynamic responses in normal mice. However, we observed anaphylactoid-type reactions and exacerbated hemodynamic events following rAd injection in mice bearing malignant 4T1 mammary carcinoma. Because 4T1 tumors induce significant CD11b(+)Gr-1(+) myeloid cell expansion and activation, we set to determine whether this causes rAd-induced exaggerated responses. When treated with a single intravenous dose (1 x 10(10) particles) of rAd, mice implanted with 4T1 carcinoma succumbed due to the anaphylactoid-type reactions. In contrast, normal mice and mice implanted with a related mammary carcinoma (66cl4) that does not induce CD11b(+)Gr-1(+) cell expansion, showed minimal responses. Depletion of phagocytic CD11b(+)Gr-1(+) cells prior to rAd delivery protected 4T1 tumor-bearing animals, whereas passive transfer of CD11b(+)Gr-1(+) cells from 4T1 tumor-bearing animals was sufficient to convey susceptibility to anaphylactoid-type reactions in normal animals. We further show that there is upregulation of nitric oxide and leukotriene signaling pathways in the 4T1 tumor-induced CD11b(+)Gr-1(+) myeloid cells and that pretreating mice with inhibitors of nitric oxide synthetase and leukotrienes can attenuate the anaphylactoid-type reactions. These data show that malignant tumor growth can alter CD11b(+)Gr-1(+) myeloid cells, rendering hosts susceptible to anaphylactoid-type reactions upon intravascular treatment with rAd.

Cell based functional assays for IDO1 inhibitor screening and characterization.

Indoleamine 2,3-dioxygenase 1 (IDO1) is a new immune-oncology target and its inhibitors have shown promise in the clinic especially in combination with other immune-stimulating agents. Here we describe two robust cell-based assays for screening IDO1 inhibitors. Both assays can be easily adopted by most laboratories and utilized for screening of IDO1 inhibitors. Endogenous IDO1 expression is induced in a cancer cell line with interferon gamma and its activity is assessed by measuring kynurenine secreted into the media. The effect of cancer cell IDO1 induction and inhibition on T cell activation is evaluated in a co-culture assay using Jurkat T cell line. Additional readouts assessing cell viability are employed for early detection of false positive IDO1 inhibitors and toxic compounds. Clinical candidates epacadostat and BMS-986205 were evaluated in the assays as control compounds, the former can completely inhibit IDO1 activity while the maximum effect of the later is limited (to about 80% in our system) consistent with the differences in their interaction with IDO1. Nanomolar concentrations of both compounds rescued IDO1 mediated inhibition of T cell activation. However, treatment with micromolar concentrations of BMS-986205 blocked Jurkat T cell activation and after prolonged incubation induced cell death.

TRAIL stabilization and cancer cell sensitization to its pro-apoptotic activity achieved through genetic fusion with arginine deiminase.

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) binds to death receptors and induces apoptosis in various cancer cell lines while sparing normal cells. Recombinant TRAIL has shown good safety and efficacy profiles in preclinical cancer models. However, clinical success has been limited due to poor PK and development of resistance to death receptor-induced apoptosis. We have addressed these issues by creating a fusion protein of TRAIL and arginine deiminase (ADI). The fusion protein benefits from structural and functional synergies between its two components and has an extended half-life in vivo. ADI downregulates survivin, upregulates DR5 receptor and sensitizes cancer cells to TRAIL induced apoptosis. ADI-TRAIL fusion protein was efficacious in a number of cell lines and synergized with some standard of care drugs. In an HCT116 xenograft model ADI-TRAIL localized to the tumor and induced dose-dependent tumor regression, the fusion protein was superior to rhTRAIL administered at the same molar amounts.

PEGylated arginine deiminase can modulate tumor immune microenvironment by affecting immune checkpoint expression, decreasing regulatory T cell accumulation and inducing tumor T cell infiltration.

PEGylated arginine deiminase (ADI-PEG 20) is being investigated in clinical studies in arginine auxotrophic cancers and is well-tolerated. The anti-tumor properties of ADI-PEG 20 have been extensively investigated - ADI-PEG 20 inhibits the growth of auxotrophic cancers in vitro and in vivo - however, its impact on immune cells is largely unknown. Here we report the potential impact of ADI-PEG 20 on the tumor immune microenvironment. ADI-PEG 20 induced immunosuppressive programmed death-ligand 1 expression on some cancer cells in vitro, but the magnitude of the increase was cell line dependent and in most relatively small. Using healthy donor human peripheral blood mononuclear cells (PBMCs) we discovered that when present during initiation of T cell activation (but not later on) ADI-PEG 20 can inhibit their differentiation after early activation stage manifested by the expression of CD69 marker. In vivo, ADI-PEG 20 induced tumor T-cell infiltration in a poorly immunogenic syngeneic mouse melanoma B16-F10 model and reduced its growth as a single agent or when combined with anti-PD-1 mAb. It was also effective by itself or in combination with anti-PD-L1 mAb in CT26 colon carcinoma syngeneic model.

Selective activation of apoptosis by a novel set of 4-aryl-3-(3-aryl-1-oxo-2-propenyl)-2(1H)-quinolinones through a Myc-dependent pathway.

Oncogene addiction due to Myc deregulation has been identified in a variety of tumor types. In order to identify pharmacological agents that cause selective apoptosis in tumors with deregulated Myc expression, we designed a cell-based screening assay based on our Anti-cancer Screening Apoptosis Program (ASAP) technology targeting increased activity in a "Myc-addicted" cancer cell panel. We have identified a novel set of substituted 4-aryl-3-(3-aryl-1-oxo-2-propenyl)-2(1H)-quinolinones that activates apoptosis in cancer cell lines with deregulated Myc, but show low activity in cell lines where Myc is not deregulated. Apoptosis induced by these compounds is rapid, and is associated with a significant downregulation of Myc protein. Selective knockdown of Myc levels in these cells by RNA interference increased sensitivity to apoptosis with compound treatment. By targeting the Myc pathway in Myc-addicted cancer cells, we have identified a novel class of apoptotic inducers that selectively and efficiently target cancer cells with deregulated Myc.

Characterization of hemodynamic events following intravascular infusion of recombinant adenovirus reveals possible solutions for mitigating cardiovascular responses.

Intravascular administration of recombinant adenovirus (rAd) in cancer patients has been well tolerated. However, dose-limiting hemodynamic responses associated with suppression of cardiac output have been observed at doses of 7.5 x 10(13) particles. While analysis of hemodynamic responses induced by small-molecule pharmaceuticals is well established, little is known about the cardiovascular effects of rAd. Telemetric cardiovascular (CV) monitoring in mice was utilized to measure hemodynamic events following intravascular rAd administration. Electrocardiogram analysis revealed a block in the SA node 3-4 min postinfusion, resulting in secondary pacemaking initiated at the AV node. This was associated with acute bradycardia, reduced blood pressure, and hypothermia followed by gradual recovery. Adenovirus-primed murine sera with high neutralizing antibody (nAb) titers could inhibit CV responses, whereas human sera with equivalent nAb titers induced by natural infection were, surprisingly, not inhibitory. Interestingly, repeat dosing within 2-4 h of the primary injection resulted in desensitization, resembling tachyphylaxis, for subsequent CV responses. Last, depletion of Kupffer cells prior to rAd infusion precluded induction of CV responses. These inhibitory effects suggest that rAd interactions with certain cells of the reticular endothelial system are associated with induction of CV responses. Significantly, these studies may provide insight into management of acute adverse effects following rAd systemic delivery, enabling a broadening of therapeutic index.

HIV-1 integrase interaction with U3 and U5 terminal sequences in vitro defined using substrates with random sequences.

Successful integration of viral genome into a host chromosome depends on interaction between viral integrase and its recognition sequences. We have used a reconstituted concerted human immunodeficiency virus, type 1 (HIV-1), integration system to analyze the role of integrase (IN) recognition sequences in formation of the IN-viral DNA complex capable of concerted integration. HIV-1 integrase was presented with substrates that contained all 4 bases at 8 mismatched positions that define the inverted repeat relationship between U3 and U5 long terminal repeats (LTR) termini and at positions 17-19, which are conserved in the termini. Evidence presented indicates that positions 17-20 of the IN recognition sequences are needed for a concerted DNA integration mechanism. All 4 bases were found at each randomized position in sequenced concerted DNA integrants, although in some instances there were preferences for specific bases. These results indicate that integrase tolerates a significant amount of plasticity as to what constitutes an IN recognition sequence. By having several positions randomized, the concerted integrants were examined for statistically significant relationships between selections of bases at different positions. The results of this analysis show not only relationships between different positions within the same LTR end but also between different positions belonging to opposite DNA termini.

Changes in the mechanism of DNA integration in vitro induced by base substitutions in the HIV-1 U5 and U3 terminal sequences.

We have reconstituted concerted human immunodeficiency virus type 1 (HIV-1) integration with specially designed mini-donor DNA, a supercoiled plasmid acceptor, purified bacterial-derived HIV-1 integrase (IN), and host HMG-I(Y) protein (Hindmarsh, P., Ridky, T., Reeves, R., Andrake, M., Skalka, A. M., and Leis, J. (1999) J. Virol. 73, 2994-3003). Integration in this system is dependent upon the mini donor DNA having IN recognition sequences at both ends and the reaction products have all of the features associated with integration of viral DNA in vivo. Using this system, we explored the relationship between the HIV-1 U3 and U5 IN recognition sequences by analyzing substrates that contain either two U3 or two U5 terminal sequences. Both substrates caused severe defects to integration but with different effects on the mechanism indicating that the U3 and the U5 sequences are both required for concerted DNA integration. We have also used the reconstituted system to compare the mechanism of integration catalyzed by HIV-1 to that of avian sarcoma virus by analyzing the effect of defined mutations introduced into U3 or U5 ends of the respective wild type DNA substrates. Despite sequence differences between avian sarcoma virus and HIV-1 IN and their recognition sequences, the consequences of analogous base pair substitutions at the same relative positions of the respective IN recognition sequences were very similar. This highlights the common mechanism of integration shared by these two different viruses.