Generation of Orthotopic Patient-Derived Xenografts in Humanized Mice for Evaluation of Emerging Targeted Therapies and Immunotherapy Combinations for Melanoma

Current methodologies for developing PDX in humanized mice in preclinical trials with immune-based therapies are limited by GVHD. Here, we compared two approaches for establishing PDX tumors in humanized mice: (1) PDX are first established in immune-deficient mice; or (2) PDX are initially established in humanized mice; then established PDX are transplanted to a larger cohort of humanized mice for preclinical trials. With the first approach, there was rapid wasting of PDX-bearing humanized mice with high levels of activated T cells in the circulation and organs, indicating immune-mediated toxicity. In contrast, with the second approach, toxicity was less of an issue and long-term human melanoma tumor growth and maintenance of human chimerism was achieved. Preclinical trials from the second approach revealed that rigosertib, but not anti-PD-1, increased CD8/CD4 T cell ratios in spleen and blood and inhibited PDX tumor growth. Resistance to anti-PD-1 was associated with PDX tumors established from tumors with limited CD8+ T cell content. Our findings suggest that it is essential to carefully manage immune editing by first establishing PDX tumors in humanized mice before expanding PDX tumors into a larger cohort of humanized mice to evaluate therapy response.

Illuminating the mechanism of IL-6-mediated immunotherapy resistance

Huseni et al. report that IL-6-STAT3 signaling negatively impacts the anti-tumor function of cytotoxic T cells. Targeting IL-6 signaling may enhance tumor responses to immune checkpoint blockade therapy.

BCL-xL inhibition potentiates cancer therapies by redirecting the outcome of p53 activation from senescence to apoptosis

Cancer therapies trigger diverse cellular responses, ranging from apoptotic death to acquisition of persistent therapy-refractory states such as senescence. Tipping the balance toward apoptosis could improve treatment outcomes regardless of therapeutic agent or malignancy. We find that inhibition of the mitochondrial protein BCL-xL increases the propensity of cancer cells to die after treatment with a broad array of oncology drugs, including mitotic inhibitors and chemotherapy. Functional precision oncology and omics analyses suggest that BCL-xL inhibition redirects the outcome of p53 transcriptional response from senescence to apoptosis, which likely occurs via caspase-dependent down-modulation of p21 and downstream cytostatic proteins. Consequently, addition of a BCL-2/xL inhibitor strongly improves melanoma response to the senescence-inducing drug targeting mitotic kinase Aurora kinase A (AURKA) in mice and patient-derived organoids. This study shows a crosstalk between the mitochondrial apoptotic pathway and cell cycle regulation that can be targeted to augment therapeutic efficacy in cancers with wild-type p53.

Treatment with soluble CD24 attenuates COVID-19-associated systemic immunopathology

Background

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19) through direct lysis of infected lung epithelial cells, which releases damage-associated molecular patterns and induces a pro-inflammatory cytokine milieu causing systemic inflammation. Anti-viral and anti-inflammatory agents have shown limited therapeutic efficacy. Soluble CD24 (CD24Fc) blunts the broad inflammatory response induced by damage-associated molecular patterns via binding to extracellular high mobility group box 1 and heat shock proteins, as well as regulating the downstream Siglec10-Src homology 2 domain–containing phosphatase 1 pathway. A recent randomized phase III trial evaluating CD24Fc for patients with severe COVID-19 (SAC-COVID; NCT04317040) demonstrated encouraging clinical efficacy.

Methods

Using a systems analytical approach, we studied peripheral blood samples obtained from patients enrolled at a single institution in the SAC-COVID trial to discern the impact of CD24Fc treatment on immune homeostasis. We performed high dimensional spectral flow cytometry and measured the levels of a broad array of cytokines and chemokines to discern the impact of CD24Fc treatment on immune homeostasis in patients with COVID-19.

Results

Twenty-two patients were enrolled, and the clinical characteristics from the CD24Fc vs. placebo groups were matched. Using high-content spectral flow cytometry and network-level analysis, we found that patients with severe COVID-19 had systemic hyper-activation of multiple cellular compartments, including CD8⁺ T cells, CD4⁺ T cells, and CD56⁺ natural killer cells. Treatment with CD24Fc blunted this systemic inflammation, inducing a return to homeostasis in NK and T cells without compromising the anti-Spike protein antibody response. CD24Fc significantly attenuated the systemic cytokine response and diminished the cytokine coexpression and network connectivity linked with COVID-19 severity and pathogenesis.

Conclusions

Our data demonstrate that CD24Fc rapidly down-modulates systemic inflammation and restores immune homeostasis in SARS-CoV-2-infected individuals, supporting further development of CD24Fc as a novel therapeutic against severe COVID-19.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-021-01222-y.

IMMUNOLOGICAL INSIGHTS INTO THE THERAPEUTIC ROLES OF CD24Fc AGAINST SEVERE COVID-19

BACKGROUND.

SARS-CoV-2 causes COVID-19 through direct lysis of infected lung epithelial cells, which releases damage-associated molecular patterns (DAMPs) and induces a pro-inflammatory cytokine milieu causing systemic inflammation. Anti-viral and anti-inflammatory agents have shown limited therapeutic efficacy. Soluble CD24 (CD24Fc) is able to blunt the broad inflammatory response induced by DAMPs in multiple models. A recent randomized phase III trial evaluating the impact of CD24Fc in patients with severe COVID-19 demonstrated encouraging clinical efficacy.

METHODS.

We studied peripheral blood samples obtained from patients enrolled at a single institution in the SAC-COVID trial (NCT04317040) collected before and after treatment with CD24Fc or placebo. We performed high dimensional spectral flow cytometry analysis of peripheral blood mononuclear cells and measured the levels of a broad array of cytokines and chemokines. A systems analytical approach was used to discern the impact of CD24Fc treatment on immune homeostasis in patients with COVID-19.

FINDINGS.

Twenty-two patients were enrolled, and the clinical characteristics from the CD24Fc vs. placebo groups were matched. Using high-content spectral flow cytometry and network-level analysis, we found systemic hyper-activation of multiple cellular compartments in the placebo group, including CD8⁺ T cells, CD4⁺ T cells, and CD56⁺ NK cells. By contrast, CD24Fc-treated patients demonstrated blunted systemic inflammation, with a return to homeostasis in both NK and T cells within days without compromising the ability of patients to mount an effective anti-Spike protein antibody response. A single dose of CD24Fc significantly attenuated induction of the systemic cytokine response, including expression of IL-10 and IL-15, and diminished the coexpression and network connectivity among extensive circulating inflammatory cytokines, the parameters associated with COVID-19 disease severity.

INTERPRETATION.

Our data demonstrates that CD24Fc treatment rapidly down-modulates systemic inflammation and restores immune homeostasis in SARS-CoV-2-infected individuals, supporting further development of CD24Fc as a novel therapeutic against severe COVID-19.

FUNDING.

NIH

Co-Clinical Imaging Resource Program (CIRP): Bridging the Translational Divide to Advance Precision Medicine

The National Institutes of Health’s (National Cancer Institute) precision medicine initiative emphasizes the biological and molecular bases for cancer prevention and treatment. Importantly, it addresses the need for consistency in preclinical and clinical research. To overcome the translational gap in cancer treatment and prevention, the cancer research community has been transitioning toward using animal models that more fatefully recapitulate human tumor biology. There is a growing need to develop best practices in translational research, including imaging research, to better inform therapeutic choices and decision-making. Therefore, the National Cancer Institute has recently launched the Co-Clinical Imaging Research Resource Program (CIRP). Its overarching mission is to advance the practice of precision medicine by establishing consensus-based best practices for co-clinical imaging research by developing optimized state-of-the-art translational quantitative imaging methodologies to enable disease detection, risk stratification, and assessment/prediction of response to therapy. In this communication, we discuss our involvement in the CIRP, detailing key considerations including animal model selection, co-clinical study design, need for standardization of co-clinical instruments, and harmonization of preclinical and clinical quantitative imaging pipelines. An underlying emphasis in the program is to develop best practices toward reproducible, repeatable, and precise quantitative imaging biomarkers for use in translational cancer imaging and therapy. We will conclude with our thoughts on informatics needs to enable collaborative and open science research to advance precision medicine.

Abstract 1054: Patient derived organoids demonstrate synergistic antitumor effect of senogenic and senolytic drug combination of Aurora kinase inhibitor and BCL2/xL inhibitor

The management of metastatic melanoma continues to be challenging, despite of evolving treatments such as immune checkpoint blockade and inhibitors of mutated BRAF. New therapies that work via immune and BRAF-independent mechanisms are urgently required for tumors that are unresponsive to currently available treatments. Here we hypothesized that combination of Aurora Kinase inhibitor (AURKAi) alisertib (senescence inducer) with a drug that selectively kills senescent cells, such as BCL2/xL inhibitor (BCLi) navitoclax (senolytic), will induce apoptosis in melanoma cells. Patient derived organoids (PDOs) were used to test anti- tumor effect of AURKAi and BCLi combination treatment. H&E staining of PDOs and their matched original tumors revealed similar histology. Fourteen out of ninety PDOs were highly sensitive to AURKAi and BCLi combination treatment exhibiting robust induction of cell death. NextGen DNA sequencing indicated that all sensitive PDOs retained wild type TP53, while resistant tumors had mutations in this gene. Knockout or knockdown of TP53 abrogated AURKAi and BCLi-induced cell death in melanoma cells, suggesting that transcription factor p53 encoded by TP53 is a key mediator of drug response. Addition of BCLi to AURKAi activated proapoptotic p53 targets BAX, NOXA and induced cleavage of PARP and Caspases 3, 7, and 8. Electron microscopy revealed morphological signs of apoptosis in combination-treated cells, including cell blebbing, apoptotic bodies, and nuclear fragmentation. This suggests that BCLi shifts cell fate decision in AURKAi-treated cells towards apoptosis. In conclusion, combination treatment with AURKAi and BCl2i induced p53-dependent apoptosis. Preclinical evaluation of this drug combination in PDO model demonstrated robust efficacy against melanomas with wild type p53. Since p53 mutations are relatively rare in melanoma, combination of AURKAi and BCLi presents promising therapeutic option for this deadly disease.

Keywords: Apoptosis, melanoma, patient-derived organoids, aurora kinase, bcl-2

Citation Format: Vijaya Bharti, Vivian Weiss, Chengli Shen, Sheau Chiann Chen, Ashlyn Blevins, Rebecca L. Shattuck-Brandt, Ann Richmond, Anna E. Vilgelm. Patient derived organoids demonstrate synergistic antitumor effect of senogenic and senolytic drug combination of Aurora kinase inhibitor and BCL2/xL inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1054.

Abstract 1578: Heating it up: Targeting RAS/RAF/PI3K pathway to make melanoma tumors ‘immunologically hot' and suitable for checkpoint blockade immunotherapies

Immune checkpoint blockade (ICB) is the current first-line treatment for metastatic melanoma. However, ICB fails in many patients and has dangerous side effects. Rigosertib (RGS), a non-ATP-competitive small molecule RAS mimetic, has the potential to block oncogenic RAS-RAF-MEK-ERK and/or PI3K-AKT-mTOR signaling pathways. Using immunocompetent mouse models of B16F10 (BRAFwt) and YUMM3.3 (BRAFmut) melanoma, we identified that RGS treatment (300mg/kg) of melanoma tumor-bearing mice is well tolerated and results in ~50% inhibition of tumor growth as monotherapy and ~70% inhibition in synergy with αPD1+αCTLA4. RGS-induced tumor inhibition depends on the induction of CD40 expression on melanoma cells, followed by immunogenic cell death, leading to an inflamed tumor microenvironment with enrichment of dendritic cells and activated CD8+ Tc cells. The RGS-initiated suppression of tumor growth was partially reversed by either suppression of CD40 expression in the melanoma cells by shRNA, or depletion of CD8+ Tc cells. Analysis of multiple published patient melanoma studies confirms that a high CD40 expression level correlates with CD80, ICOS-L, beneficial type-I T-cell responses, and better survival in melanoma patients. The CD40 levels in melanoma cells are prognostic for therapeutic response to RGS, RAF inhibitor and ICB. Notably, multiplex IHC analysis showed that BRAF inhibitor treatment significantly induces CD40+SOX10+ melanoma cells in the tumors of melanoma patients and patient-derived xenografts. Our preclinical data support the therapeutic use of RGS plus αPD1+αCTLA4 in RAS/RAF/MEK and/or PI3K pathway-activated melanoma tumors and point to the need for clinical trials to determine the clinical benefit of RGS plus ICB for metastatic melanoma patients who do not respond to ICB alone.

The authors sincerely thank Onconova Therapeutics, Newtown, PA 18940 for kindly supplying Rigosertib for this work.

Citation Format: Chi Yan, Nabil Saleh, Caroline Nebhan, Anna E. Vilgelm, E. Premkumar Reddy, Joseph T. Roland, Douglas B. Johnson, Rebecca L. Shattuck-Brandt, Sheau-Chiann Chen, Gregory D. Ayers, Ann Richmond. Heating it up: Targeting RAS/RAF/PI3K pathway to make melanoma tumors ‘immunologically hot' and suitable for checkpoint blockade immunotherapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1578.

Novel induction of CD40 expression by tumor cells with RAS/RAF/PI3K pathway inhibition augments response to checkpoint blockade

BACKGROUND

While immune checkpoint blockade (ICB) is the current first-line treatment for metastatic melanoma, it is effective for ~ 52% of patients and has dangerous side effects. The objective here was to identify the feasibility and mechanism of RAS/RAF/PI3K pathway inhibition in melanoma to sensitize tumors to ICB therapy.

METHODS

Rigosertib (RGS) is a non-ATP-competitive small molecule RAS mimetic. RGS monotherapy or in combination therapy with ICB were investigated using immunocompetent mouse models of BRAF^wt and BRAF^mut melanoma and analyzed in reference to patient data.

RESULTS

RGS treatment (300 mg/kg) was well tolerated in mice and resulted in ~ 50% inhibition of tumor growth as monotherapy and ~ 70% inhibition in combination with αPD1 + αCTLA4. RGS-induced tumor growth inhibition depends on CD40 upregulation in melanoma cells followed by immunogenic cell death, leading to enriched dendritic cells and activated T cells in the tumor microenvironment. The RGS-initiated tumor suppression was partially reversed by either knockdown of CD40 expression in melanoma cells or depletion of CD8⁺ cytotoxic T cells. Treatment with either dabrafenib and trametinib or with RGS, increased CD40⁺SOX10⁺ melanoma cells in the tumors of melanoma patients and patient-derived xenografts. High CD40 expression level correlates with beneficial T-cell responses and better survival in a TCGA dataset from melanoma patients. Expression of CD40 by melanoma cells is associated with therapeutic response to RAF/MEK inhibition and ICB.

CONCLUSIONS

Our data support the therapeutic use of RGS + αPD1 + αCTLA4 in RAS/RAF/PI3K pathway-activated melanomas and point to the need for clinical trials of RGS + ICB for melanoma patients who do not respond to ICB alone.

TRIAL REGISTRATION

NCT01205815 (Sept 17, 2010).

Cell Therapy With TILs: Training and Taming T Cells to Fight Cancer

The rationale behind cancer immunotherapy is based on the unequivocal demonstration that the immune system plays an important role in limiting cancer initiation and progression. Adoptive cell therapy (ACT) is a form of cancer immunotherapy that utilizes a patient’s own immune cells to find and eliminate tumor cells, however, donor immune cells can also be employed in some cases. Here, we focus on T lymphocyte (T cell)-based cancer immunotherapies that have gained significant attention after initial discoveries that graft-versus-tumor responses were mediated by T cells. Accumulating knowledge of T cell development and function coupled with advancements in genetics and data science has enabled the use of a patient’s own (autologous) T cells for ACT (TIL ACTs). In TIL ACT, tumor-infiltrating lymphocytes (TILs) are collected from resected tumor material, enhanced and expanded ex-vivo, and delivered back to the patient as therapeutic agents. ACT with TILs has been shown to cause objective tumor regression in several types of cancers including melanoma, cervical squamous cell carcinoma, and cholangiocarcinoma. In this review, we provide a brief history of TIL ACT and discuss the current state of TIL ACT clinical development in solid tumors. We also discuss the niche of TIL ACT in the current cancer therapy landscape and potential strategies for patient selection.

Metabolic modulation by CDK4/6 inhibitor promotes chemokine-mediated recruitment of T cells into mammary tumors

Inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6i) delay progression of metastatic breast cancer. However, complete responses are uncommon and tumors eventually relapse. Here, we show that CDK4/6i can enhance efficacy of T cell-based therapies, such as adoptive T cell transfer or T cell-activating antibodies anti-OX40/anti-4-1BB, in murine breast cancer models. This effect is driven by the induction of chemokines CCL5, CXCL9, and CXCL10 in CDK4/6i-treated tumor cells facilitating recruitment of activated CD8+ T cells, but not Tregs, into the tumor. Mechanistically, chemokine induction is associated with metabolic stress that CDK4/6i treatment induces in breast cancer cells. Despite the cell cycle arrest, CDK4/6i-treated cells retain high metabolic activity driven by deregulated PI3K/mTOR pathway. This causes cell hypertrophy and increases mitochondrial content/activity associated with oxidative stress and inflammatory stress response. Our findings uncover a link between tumor metabolic vulnerabilities and anti-tumor immunity and support further development of CDK4/6i and immunotherapy combinations.

Targeted Deletion of CXCR2 in Myeloid Cells Alters the Tumor Immune Environment to Improve Antitumor Immunity

Recruitment of myeloid-derived suppressor cells (MDSC) into the tumor microenvironment (TME) contributes to cancer immune evasion. MDSCs express the chemokine receptor CXCR2, and inhibiting CXCR2 suppresses the recruitment of MDSCs into the tumor and the premetastatic niche. Here, we compared the growth and metastasis of melanoma and breast cancer xenografts in mice exhibiting or not exhibiting targeted deletion of Cxcr2 in myeloid cells (CXCR2^myeΔ/Δ vs. CXCR2^myeWT). Detailed analysis of leukocyte populations in peripheral blood and in tumors from CXCR2^myeΔ/Δ mice revealed that loss of CXCR2 signaling in myeloid cells resulted in reduced intratumoral MDSCs and increased intratumoral CXCL11. The increase in intratumoral CXCL11 was derived in part from tumor-infiltrating B1b cells. The reduction in intratumoral MDSCs coupled with an increase in intratumoral B1b cells expressing CXCL11 resulted in enhanced infiltration and activation of effector CD8⁺ T cells in the TME of CXCR2^myeΔ/Δ mice, accompanied by inhibition of tumor growth in CXCR2^myeΔ/Δ mice compared with CXCR2^myeWT littermates. Treatment of tumor-bearing mice with a CXCR2 antagonist (SX-682) also inhibited tumor growth, reduced intratumoral MDSCs, and increased intratumoral B1b cells expressing CXCL11, leading to an increase in activated CD8⁺ T cells in the tumor. Depletion of B220⁺ cells or depletion of CD8⁺ T cells reversed the tumor-inhibitory properties in CXCR2^myeΔ/Δ mice. These data revealed a mechanism by which loss of CXCR2 signaling in myeloid cells modulates antitumor immunity through decreasing MDSCs and enriching CXCL11-producing B1b cells in the TME, which in turn increases CD8⁺ T-cell recruitment and activation in tumors.

MDM2 antagonists overcome intrinsic resistance to CDK4/6 inhibition by inducing p21

Intrinsic resistance of unknown mechanism impedes the clinical utility of inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6i) in malignancies other than breast cancer. Here, we used melanoma patient-derived xenografts (PDXs) to study the mechanisms for CDK4/6i resistance in preclinical settings. We observed that melanoma PDXs resistant to CDK4/6i frequently displayed activation of the phosphatidylinositol 3-kinase (PI3K)-AKT pathway, and inhibition of this pathway improved CDK4/6i response in a p21-dependent manner. We showed that a target of p21, CDK2, was necessary for proliferation in CDK4/6i-treated cells. Upon treatment with CDK4/6i, melanoma cells up-regulated cyclin D1, which sequestered p21 and another CDK inhibitor, p27, leaving a shortage of p21 and p27 available to bind and inhibit CDK2. Therefore, we tested whether induction of p21 in resistant melanoma cells would render them responsive to CDK4/6i. Because p21 is transcriptionally driven by p53, we coadministered CDK4/6i with a murine double minute (MDM2) antagonist to stabilize p53, allowing p21 accumulation. This resulted in improved antitumor activity in PDXs and in murine melanoma. Furthermore, coadministration of CDK4/6 and MDM2 antagonists with standard of care therapy caused tumor regression. Notably, the molecular features associated with response to CDK4/6 and MDM2 inhibitors in PDXs were recapitulated by an ex vivo organotypic slice culture assay, which could potentially be adopted in the clinic for patient stratification. Our findings provide a rationale for cotargeting CDK4/6 and MDM2 in melanoma.

Fine-Needle Aspiration-Based Patient-Derived Cancer Organoids

Patient-derived cancer organoids hold great potential to accurately model and predict therapeutic responses. Efficient organoid isolation methods that minimize post-collection manipulation of tissues would improve adaptability, accuracy, and applicability to both experimental and real-time clinical settings. Here we present a simple and minimally invasive fine-needle aspiration (FNA)-based organoid culture technique using a variety of tumor types including gastrointestinal, thyroid, melanoma, and kidney. This method isolates organoids directly from patients at the bedside or from resected tissues, requiring minimal tissue processing while preserving the histologic growth patterns and infiltrating immune cells. Finally, we illustrate diverse downstream applications of this technique including in vitro high-throughput chemotherapeutic screens, in situ immune cell characterization, and in vivo patient-derived xenografts. Thus, routine clinical FNA-based collection techniques represent an unappreciated substantial source of material that can be exploited to generate tumor organoids from a variety of tumor types for both discovery and clinical applications.

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Fine-needle aspiration (FNA) is safe, minimally invasive, and widely used clinically

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FNA is a source of material for organoid culture and personalized medicine

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This technique requires minimal processing, preserving histology, and immune cells

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Downstream applications: high-throughput screens, immune analysis, and xenografts

Metastatic Melanoma Patient-Derived Xenografts Respond to MDM2 Inhibition as a Single Agent or in Combination with BRAF/MEK Inhibition

PURPOSE

Over 60% of patients with melanoma respond to immune checkpoint inhibitor (ICI) therapy, but many subsequently progress on these therapies. Second-line targeted therapy is based on BRAF mutation status, but no available agents are available for NRAS, NF1, CDKN2A, PTEN, and TP53 mutations. Over 70% of melanoma tumors have activation of the MAPK pathway due to BRAF or NRAS mutations, while loss or mutation of CDKN2A occurs in approximately 40% of melanomas, resulting in unregulated MDM2-mediated ubiquitination and degradation of p53. Here, we investigated the therapeutic efficacy of over-riding MDM2-mediated degradation of p53 in melanoma with an MDM2 inhibitor that interrupts MDM2 ubiquitination of p53, treating tumor-bearing mice with the MDM2 inhibitor alone or combined with MAPK-targeted therapy.

EXPERIMENTAL DESIGN

To characterize the ability of the MDM2 antagonist, KRT-232, to inhibit tumor growth, we established patient-derived xenografts (PDX) from 15 patients with melanoma. Mice were treated with KRT-232 or a combination with BRAF and/or MEK inhibitors. Tumor growth, gene mutation status, as well as protein and protein-phosphoprotein changes, were analyzed.

RESULTS

One-hundred percent of the 15 PDX tumors exhibited significant growth inhibition either in response to KRT-232 alone or in combination with BRAF and/or MEK inhibitors. Only BRAFV600WT tumors responded to KRT-232 treatment alone while BRAFV600E/M PDXs exhibited a synergistic response to the combination of KRT-232 and BRAF/MEK inhibitors.

CONCLUSIONS

KRT-232 is an effective therapy for the treatment of either BRAFWT or PAN WT (BRAFWT, NRASWT) TP53WT melanomas. In combination with BRAF and/or MEK inhibitors, KRT-232 may be an effective treatment strategy for BRAFV600-mutant tumors.

Abstract B20: Patient-derived organoids demonstrate synergistic effect of co-targeting Aurora kinase and prosurvival BCL2 family proteins

Many melanomas are resistant to standard-of-care immune checkpoint blockade and inhibitors of mutated BRAF. New effective therapies that work via immune and BRAF-independent mechanisms are urgently needed. We have previously demonstrated that an inhibitor of mitotic kinase Aurora A (AURKAi) can induce a distinct type of stable cell cycle known as senescence in melanoma tumors independent of their genetic background. Here we hypothesized that combination of AURKAi with a drug that selectively kills senescent cells, such as BCL2 inhibitor (BCLi) navitoclax, will be synthetically lethal to melanoma cells. Melanoma patient-derived organoids (PDOs) were used to test efficacy of AURKAi and BCLi combination treatment. To generate organoids, patient-derived tumor cells were cultured ex vivo in 3D matrix. Drug response was evaluated using fluorescent viability assay. Fifteen out of twenty PDOs were highly sensitive to AURKAi and BCLi combination treatment, exhibiting robust induction of cell death. No cell death was observed when either drug was added individually. NextGen DNA sequencing indicated that all sensitive PDOs retained wild-type TP53, while resistant tumors had mutations in this gene. Knockout or knockdown of TP53 abrogated AURKAi and BCLi-induced cell death in melanoma cells, suggesting that transcription factor p53 encoded by TP53 is a key mediator of drug response. Mechanistically, p53 was induced by AURKAi treatment independent of BCLi. However, single-agent AURKAi treatment resulted in activation of p53-mediated cell cycle arrest based on increased expression of CDK inhibitor p21 and decreased expression of proliferation markers. In contrast, addition of BCLi to AURKAi activated proapoptotic p53 target BAX and induced cleavage of PARP and caspases 3, 7, and 8. Treatment with pan-caspase inhibitor abrogated cell death, suggesting caspase-dependent apoptosis. Electron microscopy revealed morphologic signs of apoptosis in combination-treated cells, including cell blebbing, apoptotic bodies, and nuclear fragmentation. This suggests that BCLi shifts cell fate decision in AURKAi-treated cells towards apoptosis. In conclusion, combination treatment with AURKAi and BCl2i induced p53-dependent apoptosis. Preclinical evaluation of this drug combination in PDO model demonstrated robust efficacy against melanomas with wild-type p53. Since p53 mutations are relatively rare in melanoma, a combination of AURKAi and BCLi presents a promising therapeutic option for this deadly disease.

Citation Format: Vijaya Bharti, Ashlyn Blevins, Vivian L. Weiss, Sheau C Chen, Roman Uzhachenko, Ann Richmond, Anna E. Vilgelm. Patient-derived organoids demonstrate synergistic effect of co-targeting Aurora kinase and prosurvival BCL2 family proteins [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr B20.

Multimodal Multiplexed Immunoimaging with Nanostars to Detect Multiple Immunomarkers and Monitor Response to Immunotherapies

The overexpression of immunomarker programmed cell death protein 1 (PD-1) and engagement of PD-1 to its ligand, PD-L1, are involved in the functional impairment of cluster of differentiation 8+ (CD8+) T cells, contributing to cancer progression. However, heterogeneities in PD-L1 expression and variabilities in biopsy-based assays render current approaches inaccurate in predicting PD-L1 status. Therefore, PD-L1 screening alone is not predictive of patient response to treatment, which motivates us to simultaneously detect multiple immunomarkers engaged in immune modulation. Here, we have developed multimodal probes, immunoactive gold nanostars (IGNs), that accurately detect PD-L1+ tumor cells and CD8+ T cells simultaneously in vivo, surpassing the limitations of current immunoimaging techniques. IGNs integrate the whole-body imaging of positron emission tomography with high sensitivity and multiplexing of Raman spectroscopy, enabling the dynamic tracking of both immunomarkers. IGNs also monitor response to immunotherapies in mice treated with combinatorial PD-L1 and CD137 agonists and distinguish responders from those nonresponsive to treatment. Our results showed a multifunctional nanoscale probe with capabilities that cannot be achieved with either modality alone, allowing multiplexed immunologic tumor profiling critical for predicting early response to immunotherapies.

Chemokines Modulate Immune Surveillance in Tumorigenesis, Metastasis, and Response to Immunotherapy

Chemokines are small secreted proteins that orchestrate migration and positioning of immune cells within the tissues. Chemokines are essential for the function of the immune system. Accumulating evidence suggest that chemokines play important roles in tumor microenvironment. In this review we discuss an association of chemokine expression and activity within the tumor microenvironment with cancer outcome. We summarize regulation of immune cell recruitment into the tumor by chemokine-chemokine receptor interactions and describe evidence implicating chemokines in promotion of the "inflamed" immune-cell enriched tumor microenvironment. We review both tumor-promoting function of chemokines, such as regulation of tumor metastasis, and beneficial chemokine roles, including stimulation of anti-tumor immunity and response to immunotherapy. Finally, we discuss the therapeutic strategies target tumor-promoting chemokines or induce/deliver beneficial chemokines within the tumor focusing on pre-clinical studies and clinical trials going forward. The goal of this review is to provide insight into comprehensive role of chemokines and their receptors in tumor pathobiology and treatment.

Loss of CXCR4 in Myeloid Cells Enhances Antitumor Immunity and Reduces Melanoma Growth through NK Cell and FASL Mechanisms

The chemokine receptor, CXCR4, is involved in cancer growth, invasion, and metastasis. Several promising CXCR4 antagonists have been shown to halt tumor metastasis in preclinical studies, and clinical trials evaluating the effectiveness of these agents in patients with cancer are ongoing. However, the impact of targeting CXCR4 specifically on immune cells is not clear. Here, we demonstrate that genetic deletion of CXCR4 in myeloid cells (CXCR4^MyeΔ/Δ) enhances the antitumor immune response, resulting in significantly reduced melanoma tumor growth. Moreover, CXCR4^MyeΔ/Δ mice exhibited slowed tumor progression compared with CXCR4^WT mice in an inducible melanocyte Braf^V600E/Pten ^-/- mouse model. The percentage of Fas ligand (FasL)-expressing myeloid cells was reduced in CXCR4^MyeΔ/Δ mice as compared with myeloid cells from CXCR4^WT mice. In contrast, there was an increased percentage of natural killer (NK) cells expressing FasL in tumors growing in CXCR4^MyeΔ/Δ mice. NK cells from CXCR4^MyeΔ/Δ mice also exhibited increased tumor cell killing capacity in vivo, based on clearance of NK-sensitive Yac-1 cells. NK cell-mediated killing of Yac-1 cells occurred in a FasL-dependent manner, which was partially dependent upon the presence of CXCR4^MyeΔ/Δ neutrophils. Furthermore, enhanced NK cell activity in CXCR4^MyeΔ/Δ mice was also associated with increased production of IL18 by specific leukocyte subpopulations. These data suggest that CXCR4-mediated signals from myeloid cells suppress NK cell-mediated tumor surveillance and thereby enhance tumor growth. Systemic delivery of a peptide antagonist of CXCR4 to tumor-bearing CXCR4^WT mice resulted in enhanced NK-cell activation and reduced tumor growth, supporting potential clinical implications for CXCR4 antagonism in some cancers. Cancer Immunol Res; 6(10); 1186-98. ©2018 AACR.

Abstract 4948: MDM2 antagonism overcomes resistance to CDK4/6 inhibition in melanoma

Metastatic melanoma is an aggressive disease characterized by resistance to conventional cancer treatments such as radiation and chemotherapy. While immune checkpoint blockade and BRAF inhibitor therapies are effective in many melanoma cases, a significant proportion of patients are resistant to these standard of care treatments and thus require new therapeutic approaches. We hypothesized that targeting CDK4/6 may offer hope to melanoma patients refractory to immunotherapy and BRAF inhibition, based on CDK4 being a key oncogene activated by mutations or deletions of CDKN2A gene, which are very common in melanoma (>50% of cases). However, in vivo studies using our extensive collection of melanoma patient-derived xenografts (PDX) showed that the majority of melanoma tumors are intrinsically resistant to CDK4/6 inhibition. We identified the mechanism of this resistance which was driven by cooperative activities of other CDKs expressed by tumor cells that compensated for the loss of CDK4/6 function to allow cell cycle progression through G1 and S phases. In order to overcome compensatory activation of other CDKs, we used small molecule antagonists of MDM2-p53 interaction, that stabilize p53 protein, which, in turn, upregulates an endogenous pan-CDK inhibitor, p21. Notably, combined MDM2 and CDK4/6 antagonism resulted in greater inhibition of tumor growth than either inhibitor individually. This synergistic effect was observed in multiple melanoma PDX models and in immunocompetent mice bearing mouse melanoma tumors. In summary, our preclinical data suggest that combining CDK4/6 inhibitors with MDM2 antagonists is a promising strategy for the treatment of metastatic melanoma, which should be further tested by a clinical study.

Citation Format: Anna E. Vilgelm, Nabil Saleh, Kelsie Riemenschneider, Lauren Slesur, Sheau-Chian Chen, Gregory D. Ayers, Rondi M. Kauffman, Mark C. Kelley, Douglas B. Johnson, Ann Richmond. MDM2 antagonism overcomes resistance to CDK4/6 inhibition in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4948.

Abstract 513: The link between polyploidy and replication stress in melanoma

Genomic instability is a hallmark of cancer implicated in tumor evolution and resistance to therapy. However, the molecular mechanisms that underlie genomic instability are still poorly understood. One common feature of cancer cells is an elevated genomic content (polyploidy) which is also associated with the acquisition of therapy resistance. Here we demonstrate a link between genomic instability and polyploidization in melanoma cells. We show that polyploidy induced by treatment with small molecule inhibitors of various mitotic kinases, such as AURKA, AURKB and PLK1, leads to DNA damage in cells with elevated (>4n) DNA content. This DNA damage results from replication stress exacerbated by limited activation of p53 in malignant melanocytes. Pharmacological induction of p53 in polyploid cells using an MDM2 antagonist reduced DNA damage by blocking re-replication of the polyploid genome as a result of p53-mediated p21 activation and transactivation of DNA repair genes. Notably we found that p21 blockade using siRNA knockdown or genetic knockout shifted polypoid cell response to p53 activation from cytostatic to cytotoxic. As a result, p21-deficient cells exhibited enhanced sensitivity to mitotic blockade combined with p53 induction. Furthermore, TCGA dataset analysis showed poor progression free survival in melanoma patients with high p21 protein expression. These data argue for administering mitotic inhibitors and MDM2 antagonists, which are currently in clinical development, in conjunction with agents that target p21. In summary, our data here reveal that polyploidization can be a mechanism for induction of DNA damage and genomic instability associated with drug resistance in cancer and suggest a novel strategy for targeting these pathways to improve melanoma therapy.

Citation Format: Anna E. Vilgelm, C. Andrew Johnson, Kiran Malikayil, Dayanidhi Raman, David Flaherty, Brian Higgins, Ann Richmond. The link between polyploidy and replication stress in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 513. doi:10.1158/1538-7445.AM2017-513

PI3K Inhibition Reduces Mammary Tumor Growth and Facilitates Antitumor Immunity and Anti-PD1 Responses

Purpose: Metastatic breast cancers continue to elude current therapeutic strategies, including those utilizing PI3K inhibitors. Given the prominent role of PI3Kα,β in tumor growth and PI3Kγ,δ in immune cell function, we sought to determine whether PI3K inhibition altered antitumor immunity.Experimental Design: The effect of PI3K inhibition on tumor growth, metastasis, and antitumor immune response was characterized in mouse models utilizing orthotopic implants of 4T1 or PyMT mammary tumors into syngeneic or PI3Kγ-null mice, and patient-derived breast cancer xenografts in humanized mice. Tumor-infiltrating leukocytes were characterized by IHC and FACS analysis in BKM120 (30 mg/kg, every day) or vehicle-treated mice and PI3Kγ^null versus PI3Kγ^WT mice. On the basis of the finding that PI3K inhibition resulted in a more inflammatory tumor leukocyte infiltrate, the therapeutic efficacy of BKM120 (30 mg/kg, every day) and anti-PD1 (100 μg, twice weekly) was evaluated in PyMT tumor-bearing mice.Results: Our findings show that PI3K activity facilitates tumor growth and surprisingly restrains tumor immune surveillance. These activities could be partially suppressed by BKM120 or by genetic deletion of PI3Kγ in the host. The antitumor effect of PI3Kγ loss in host, but not tumor, was partially reversed by CD8⁺ T-cell depletion. Treatment with therapeutic doses of both BKM120 and antibody to PD-1 resulted in consistent inhibition of tumor growth compared with either agent alone.Conclusions: PI3K inhibition slows tumor growth, enhances antitumor immunity, and heightens susceptibility to immune checkpoint inhibitors. We propose that combining PI3K inhibition with anti-PD1 may be a viable therapeutic approach for triple-negative breast cancer. Clin Cancer Res; 23(13); 3371-84. ©2016 AACR.

Combinatorial approach to cancer immunotherapy: strength in numbers

Immune-checkpoint blockade therapy with antibodies targeting CTLA-4 and PD-1 has revolutionized melanoma treatment by eliciting responses that can be remarkably durable and is now advancing to other malignancies. However, not all patients respond to immune-checkpoint inhibitors. Extensive preclinical evidence suggests that combining immune-checkpoint inhibitors with other anti-cancer treatments can greatly improve the therapeutic benefit. The first clinical success of the combinatorial approach to cancer immunotherapy was demonstrated using a dual-checkpoint blockade with CTLA-4 and PD-1 inhibitors, which resulted in accelerated FDA approval of this therapeutic regimen. In this review, we discuss the combinations of current and emerging immunotherapeutic agents in clinical and preclinical development and summarize the insights into potential mechanisms of synergistic anti-tumor activity gained from animal studies. These promising combinatorial partners for the immune-checkpoint blockade include therapeutics targeting additional inhibitory receptors of T cells, such as TIM-3, LAG-3, TIGIT, and BTLA, and agonists of T cell costimulatory receptors 4-1BB, OX40, and GITR, as well as agents that promote cancer cell recognition by the immune system, such as tumor vaccines, IDO inhibitors, and agonists of the CD40 receptor of APCs. We also review the therapeutic potential of regimens combining the immune-checkpoint blockade with therapeutic interventions that have been shown to enhance immunogenicity of cancer cells, including oncolytic viruses, RT, epigenetic therapy, and senescence-inducing therapy.

Abstract 5126: The link between therapy-induced senescence and anti-tumor immune microenvironment in melanoma

Tumor cell senescence is often induced by cancer therapeutics. Senescent cells secrete many proteins that may affect both malignant and non-malignant components of the tumor. The goal of this study was to determine how therapy-induced senescence (TIS) affects the immune microenvironment in melanoma. We used inhibitors of cell cycle kinases AURKA and CDK4/6 (AURKAi, CDK4/6i) to induce senescence in melanoma tumors. RNA sequencing analysis of AURKAi-treated syngeneic mouse tumors demonstrated that response to AURKA inhibition was strongly associated with induction of an immune transcriptome (p = 3.5E-29). Immunofluorescent staining and flow cytometric analysis of digested tumors showed correlation between the numbers of tumor-infiltrating leukocytes (TILs) and AURKAi response (Spearman r = -0.87, p<0.001). T cells were among the TILs recruited into AURKAi-sensitive tumors. Therapeutic benefit of AURKAi was limited in immunodeficient host (67% of tumors regressed in immunocompetent mice vs 0% in immunodeficient mice, p = 0.01) suggesting that recruitment of TILs augments response to senescence-inducing therapy. We found that TILs were driven into tumors in response to chemokine CCL5 that was induced in AURKAi and CDK4/6i-treated melanoma cells (up to 20 fold, p≤0.005) on mRNA and secreted protein levels. Knockdown of CCL5 (KD) inhibited leukocyte recruitment (6.8% in KD vs 29.5% in control, p = 0.002) and response to AURKAi in vivo (p = 0.61 in KD vs p = 0.02 in control). In contrast, therapeutic benefit was greatly enhanced when senescence-inducing therapy was combined with T cell-activating immunotherapy using CD137 (4-1BB) agonist (p<0.001). We also evaluated CCL5 expression in human melanoma tumors in relation with TIS and TIL markers. Expression of CCL5 was induced by AURKAi and/or CDK4/6i in patient derived xenografts (3 patients, 3 mice each, p≤0.02), in tumors from patients who responded on AURKAi clinical trial (3 patients, before/after therapy) and was associated with expression of “Immune response” genes in The Cancer Genome Atlas (TCGA) dataset of 278 melanoma tumors (p = 1.40E-93). In conclusion, our data demonstrates that TIS promotes recruitment of TILs via the induction of CCL5 which, in turn, augment therapeutic response in melanoma. Further improvement of melanoma outcome is achieved when senescence-inducing drugs are combined with immunotherapy that promotes tumor cells killing by TILs. This study presents a novel promising approach to improve melanoma therapy by utilizing TIS to reprogram tumor immune microenvironment.

Citation Format: Anna E. Vilgelm, C Andrew Johnson, Nripesh Prasad, Jinming Yang, Sheau-Chiann Chen, Gregory D. Ayers, Jeffrey A. Sosman, Jeffrey A. Ecsedy, Shyr Yu, Shawn E. Levy, Ann Richmond. The link between therapy-induced senescence and anti-tumor immune microenvironment in melanoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5126.

Melanoma-specific MHC-II expression represents a tumour-autonomous phenotype and predicts response to anti-PD-1/PD-L1 therapy

Anti-PD-1 therapy yields objective clinical responses in 30-40% of advanced melanoma patients. Since most patients do not respond, predictive biomarkers to guide treatment selection are needed. We hypothesize that MHC-I/II expression is required for tumour antigen presentation and may predict anti-PD-1 therapy response. In this study, across 60 melanoma cell lines, we find bimodal expression patterns of MHC-II, while MHC-I expression was ubiquitous. A unique subset of melanomas are capable of expressing MHC-II under basal or IFNγ-stimulated conditions. Using pathway analysis, we show that MHC-II(+) cell lines demonstrate signatures of 'PD-1 signalling', 'allograft rejection' and 'T-cell receptor signalling', among others. In two independent cohorts of anti-PD-1-treated melanoma patients, MHC-II positivity on tumour cells is associated with therapeutic response, progression-free and overall survival, as well as CD4(+) and CD8(+) tumour infiltrate. MHC-II(+) tumours can be identified by melanoma-specific immunohistochemistry using commercially available antibodies for HLA-DR to improve anti-PD-1 patient selection.

Connecting the Dots: Therapy-Induced Senescence and a Tumor-Suppressive Immune Microenvironment

BACKGROUND

Tumor cell senescence is a common outcome of anticancer therapy. Here we investigated how therapy-induced senescence (TIS) affects tumor-infiltrating leukocytes (TILs) and the efficacy of immunotherapy in melanoma.

METHODS

Tumor senescence was induced by AURKA or CDK4/6 inhibitors (AURKAi, CDK4/6i). Transcriptomes of six mouse tumors with differential response to AURKAi were analyzed by RNA sequencing, and TILs were characterized by flow cytometry. Chemokine RNA and protein expression were determined by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay. Therapeutic response was queried in immunodeficient mice, in mice with CCL5-deficient tumors, and in mice cotreated with CD137 agonist to activate TILs. CCL5 expression in reference to TIS and markers of TILs was studied in human melanoma tumors using patient-derived xenografts (n = 3 patients, n = 3 mice each), in AURKAi clinical trial samples (n = 3 patients, before/after therapy), and in The Cancer Genome Atlas (n = 278). All statistical tests were two-sided.

RESULTS

AURKAi response was associated with induction of the immune transcriptome (P = 3.5 x 10-29) while resistance inversely correlated with TIL numbers (Spearman r = -0.87, P < .001). AURKAi and CDK4/6i promoted the recruitment of TILs by inducing CCL5 secretion in melanoma cells (P ≤ .005) in an NF-κB-dependent manner. Therapeutic response to AURKAi was impaired in immunodeficient compared with immunocompetent mice (0% vs 67% tumors regressed, P = .01) and in mice bearing CCL5-deficient vs control tumors (P = .61 vs P = .02); however, AURKAi response was greatly enhanced in mice also receiving T-cell-activating immunotherapy (P < .001). In human tumors, CCL5 expression was also induced by AURKAi (P ≤ .02) and CDK4/6i (P = .01) and was associated with increased immune marker expression (P = 1.40 x 10-93).

CONCLUSIONS

Senescent melanoma cells secret CCL5, which promotes recruitment of TILs. Combining TIS with immunotherapy that enhances tumor cell killing by TILs is a promising novel approach to improve melanoma outcomes.

Abstract B12: Synergistic anticancer activity of Aurora A kinase and MDM2 antagonists in melanoma

Senescence-inducing therapies can block proliferation of malignant cells and promote anti-tumor immune activity. However, the risk of tumor relapse remains high due to the long lifespan of senescence cells with potential to escape senescence. Here our preclinical studies demonstrate that combining a senescent-inducing aurora kinase A (AURKA) inhibitor alisertib (MLN8237) with an MDM2 antagonist [(-)-nutlin 3a] effectively induces robust p53 activation in senescent Tp53WT tumors accompanied by: 1) tumor cell proliferation arrest; 2) mitochondrial depolarization and tumor cell apoptosis; and 3) tumor cell clearance via CCL5-, CCL1- and CCL9-mediated recruitment of anti-tumor leukocytes. This combined therapy shows adequate bioavailability and low toxicity to the host in the mouse model. Moreover, the prominent preclinical response of patient-derived melanoma tumors to the co-targeting of MDM2 and AURKA provides rationale for further investigation of alisertib and MDM2 inhibitors.

Citation Format: Anna E. Vilgelm, Jeff S. Pawlikowski, Yan Liu, E. Hawkins Oriana, A. Davis Tyler, Kevin P. Weller, Linda W. Horton, Colt M. McClain, Gregory D. Ayers, David Turner, David C. Essaka, Clinton F. Stewart, Jeffrey A. Sosman, Mark C. Kelley, Jeffrey A. Ecsedy, Jeffrey N. Johnston, Ann Richmond. Synergistic anticancer activity of Aurora A kinase and MDM2 antagonists in melanoma. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Melanoma: From Biology to Therapy; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(14 Suppl):Abstract nr B12.

Combining an Aurora Kinase Inhibitor and a Death Receptor Ligand/Agonist Antibody Triggers Apoptosis in Melanoma Cells and Prevents Tumor Growth in Preclinical Mouse Models

PURPOSE

Preclinical studies show that inhibition of aurora kinases in melanoma tumors induces senescence and reduces tumor growth, but does not cause tumor regression. Additional preclinical models are needed to identify agents that will synergize with aurora kinase inhibitors to induce tumor regression.

EXPERIMENTAL DESIGN

We combined treatment with an aurora kinase A inhibitor, MLN8237, with agents that activate death receptors (Apo2L/TRAIL or death receptor 5 agonists) and monitored the ability of this treatment to induce tumor apoptosis and melanoma tumor regression using human cell lines and patient-derived xenograft (PDX) mouse models.

RESULTS

We found that this combined treatment led to apoptosis and markedly reduced cell viability. Mechanistic analysis showed that the induction of tumor cell senescence in response to the AURKA inhibitor resulted in a decreased display of Apo2L/TRAIL decoy receptors and increased display of one Apo2L/TRAIL receptor (death receptor 5), resulting in enhanced response to death receptor ligand/agonists. When death receptors were activated in senescent tumor cells, both intrinsic and extrinsic apoptotic pathways were induced independent of BRAF, NRAS, or p53 mutation status. Senescent tumor cells exhibited BID-mediated mitochondrial depolarization in response to Apo2L/TRAIL treatment. In addition, senescent tumor cells had a lower apoptotic threshold due to decreased XIAP and survivin expression. Melanoma tumor xenografts of one human cell line and one PDX displayed total blockage of tumor growth when treated with MLN8237 combined with DR5 agonist antibody.

CONCLUSIONS

These findings provide a strong rationale for combining senescence-inducing therapeutics with death receptor agonists for improved cancer treatment.

Mdm2 and aurora kinase a inhibitors synergize to block melanoma growth by driving apoptosis and immune clearance of tumor cells

Therapeutics that induce cancer cell senescence can block cell proliferation and promote immune rejection. However, the risk of tumor relapse due to senescence escape may remain high due to the long lifespan of senescent cells that are not cleared. Here, we show how combining a senescence-inducing inhibitor of the mitotic kinase Aurora A (AURKA) with an MDM2 antagonist activates p53 in senescent tumors harboring wild-type 53. In the model studied, this effect is accompanied by proliferation arrest, mitochondrial depolarization, apoptosis, and immune clearance of cancer cells by antitumor leukocytes in a manner reliant upon Ccl5, Ccl1, and Cxcl9. The AURKA/MDM2 combination therapy shows adequate bioavailability and low toxicity to the host. Moreover, the prominent response of patient-derived melanoma tumors to coadministered MDM2 and AURKA inhibitors offers a sound rationale for clinical evaluation. Taken together, our work provides a preclinical proof of concept for a combination treatment that leverages both senescence and immune surveillance to therapeutic ends.

Preparation of (-)-Nutlin-3 using enantioselective organocatalysis at decagram scale

Chiral nonracemic cis-4,5-bis(aryl)imidazolines have emerged as a powerful platform for the development of cancer chemotherapeutics, stimulated by the Hoffmann-La Roche discovery that Nutlin-3 can restore apoptosis in cells with wild-type p53. The lack of efficient methods for the enantioselective synthesis of cis-imidazolines, however, has limited their more general use. Our disclosure of the first enantioselective synthesis of (-)-Nutlin-3 provided a basis to prepare larger amounts of this tool used widely in cancer biology. Key to the decagram-scale synthesis described here was the discovery of a novel bis(amidine) organocatalyst that provides high enantioselectivity at warmer reaction temperature (-20 °C) and low catalyst loadings. Further refinements to the procedure led to the synthesis of (-)-Nutlin-3 in a 17 g batch and elimination of all but three chromatographic purifications.

Targeting aurora kinases limits tumour growth through DNA damage-mediated senescence and blockade of NF-κB impairs this drug-induced senescence

Oncogene-induced senescence can provide a protective mechanism against tumour progression. However, production of cytokines and growth factors by senescent cells may contribute to tumour development. Thus, it is unclear whether induction of senescence represents a viable therapeutic approach. Here, using a mouse model with orthotopic implantation of metastatic melanoma tumours taken from 19 patients, we observed that targeting aurora kinases with MLN8054/MLN8237 impaired mitosis, induced senescence and markedly blocked proliferation in patient tumour implants. Importantly, when a subset of tumour-bearing mice were monitored for tumour progression after pausing MLN8054 treatment, 50% of the tumours did not progress over a 12-month period. Mechanistic analyses revealed that inhibition of aurora kinases induced polyploidy and the ATM/Chk2 DNA damage response, which mediated senescence and a NF-κB-related, senescence-associated secretory phenotype (SASP). Blockade of IKKβ/NF-κB led to reversal of MLN8237-induced senescence and SASP. Results demonstrate that removal of senescent tumour cells by infiltrating myeloid cells is crucial for inhibition of tumour re-growth. Altogether, these data demonstrate that induction of senescence, coupled with immune surveillance, can limit melanoma growth.

Abstract 5602: Molecular mechanism underlying acquired resistance to Aurora A kinase inhibitor, Alisertib, in melanoma

Malignant melanomas are notorious for their resistance to chemotherapeutic treatments. Thus the development of new therapeutic strategies that will allow overcoming drug resistance is essential. We have previously shown that Aurora A kinase (AurkA) inhibitor Alisertib (MLN8237) inhibited melanoma cell grouth by blocking mitosis and inducing senescence. In this study we used melanoma patients’ tissue specimens implanted under the skin of athymic mice and mouse melanoma tumors grown in immune-competent mice. Treatment with Alisertib inhibited melanoma tumor growth in both model systems. However, most of tumors re-grew after the treatment was paused and some of them acquired resistance to a second round of chemotherapy. Interestingly mouse melanoma cells collected from chemo-resistant tumors retained their resistance to Alisertib treatment when re-implanted into new hosts. In order to gain understanding of the molecular events facilitating Alisertib resistance we performed whole transcriptome sequencing in mouse melanoma tumors. Each Alisertib-treated tumor showed a large number of genomic alterations with the number of single nucleotide variations in protein-coding transcripts ranging from 807 to 2036. In total 613 genes were affected across 6 analyzed samples and among those, 253 genes carried nucleotide variations exclusively in drug resistant tumors. In silico pathway analysis revealed a statistically significant enrichment of this resistance-associated gene set with genes involved in cell cycle regulation (p&lt;0.0001). Among those were important regulators of cell cycle checkpoints, DNA repair and DNA damage response such as p53, Sesn3, TSC2, Camk2d, Lig1, Usp19, Slbp, Dgkz and Rpl24. This data together with our previous findings that that Alisertib induces polyploidy and subsequent activation of DNA damage response suggests that endoreduplication (DNA re-replication after failed mitosis) may promote the development of chemo-resistance in melanomas. We also found that Alisertib-induced endoreduplication can be blocked through activation of endogenous p53. Treatment with inhibitor of p53 degradation, Nutlin-3, significantly reduced Alisertib-associated polyploidy by inhibiting Rb phosphorylation and expression of genes involved in DNA replication licensing. This coincided with a decrease in phosphorylation levels of DNA-damage sensor histone H2AX and effector kinase Chk2. Notably, co-treatment with Nutlin-3 neither rescued melanoma cells from cytostatic effect of Alisertib treatment nor reversed Alisertib-induced senescence. Our findings suggest that pharmacological activation of endogenous p53 in combination with AurkA inhibitors could block endoreduplication-related genomic instability and potentially delay the development of drug resistance in melanoma tumors. This work was supported by grants from the NIH (CA116021-07) and VCORCDP (CA90625-11).

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 5602. doi:1538-7445.AM2012-5602

RAF265 inhibits the growth of advanced human melanoma tumors

PURPOSE

The purpose of this preclinical study was to determine the effectiveness of RAF265, a multikinase inhibitor, for treatment of human metastatic melanoma and to characterize traits associated with drug response.

EXPERIMENTAL DESIGN

Advanced metastatic melanoma tumors from 34 patients were orthotopically implanted to nude mice. Tumors that grew in mice (17 of 34) were evaluated for response to RAF265 (40 mg/kg, every day) over 30 days. The relation between patient characteristics, gene mutation profile, global gene expression profile, and RAF265 effects on tumor growth, mitogen-activated protein/extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK) phosphorylation, proliferation, and apoptosis markers was evaluated.

RESULTS

Nine of the 17 tumors that successfully implanted (53%) were mutant BRAF (BRAF(V600E/K)), whereas eight of 17 (47%) tumors were BRAF wild type (BRAF(WT)). Tumor implants from 7 of 17 patients (41%) responded to RAF265 treatment with more than 50% reduction in tumor growth. Five of the 7 (71%) responders were BRAF(WT), of which 1 carried c-KIT(L576P) and another N-RAS(Q61R) mutation, while only 2 (29%) of the responding tumors were BRAF(V600E/K). Gene expression microarray data from nonimplanted tumors revealed that responders exhibited enriched expression of genes involved in cell growth, proliferation, development, cell signaling, gene expression, and cancer pathways. Although response to RAF265 did not correlate with pERK1/2 reduction, RAF265 responders did exhibit reduced pMEK1, reduced proliferation based upon reduced Ki-67, cyclin D1 and polo-like kinase1 levels, and induction of the apoptosis mediator BCL2-like 11.

CONCLUSIONS

Orthotopic implants of patient tumors in mice may predict prognosis and treatment response for melanoma patients. A subpopulation of human melanoma tumors responds to RAF265 and can be characterized by gene mutation and gene expression profiles.

[The coordinated interaction of multifunctional members of p53 family determines many key processes in multicellular organisms]

First time p53 was found in the complex with viral large T-antigene in the cells transformed by small DNA virus SV40. The cloning of p53 cDNA was done in the beginning of eighties and soon after that the whole p53 gene was cloned. The p53 family is comprised of three genes: TP53,TP63 and TP73, each of which is expressed as a set of structurally and functionally different isoforms. All of them intensively interact with each other forming a united functional network of proteins. In this review we discuss evolution of the p53 family and significance of all its members in embryonic development, reproduction, regeneration, regulation of aging and life span, as well as in the body's defense against cancer. With special attention we review the role of less studied members of the p53 family: p63 and p73, in oncogenesis and tumor progression and show that different isoforms of these proteins might exert a contrary effect on these processes.

Interactions of the p53 protein family in cellular stress response in gastrointestinal tumors

p53, p63, and p73 are members of the p53 protein family involved in regulation of cell cycle, apoptosis, differentiation, and other critical cellular processes. Here, we investigated the contribution of the entire p53 family in chemotherapeutic drug response in gastrointestinal tumors. Real-time PCR and immunohistochemistry revealed complexity and variability of expression profiles of the p53 protein family. Using colon and esophageal cancer cells, we found that the integral transcription activity of the entire p53 family, as measured by the reporter analysis, associated with response to drug treatment in studied cells. We also found that p53 and p73, as well as p63 and p73, bind simultaneously to the promoters of p53 target genes. Taken together, our results support the view that the p53 protein family functions as an interacting network of proteins and show that cellular responses to chemotherapeutic drug treatment are determined by the total activity of the entire p53 family rather than p53 alone.