Oriana E. Hawkins

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.

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 (BRAFV600E/K), whereas eight of 17 (47%) tumors were BRAF wild type (BRAFWT). 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 BRAFWT, of which 1 carried c-KITL576P and another N-RASQ61R mutation, while only 2 (29%) of the responding tumors were BRAFV600E/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. Clin Cancer Res; 18(8); 2184–98. ©2012 AACR.

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.

Passage-dependent cancerous transformation of human mesenchymal stem cells under carcinogenic hypoxia

Bone marrow‐derived human mesenchymal stem cells (hMSCs) either promote or inhibit cancer progression, depending on factors that heretofore have been undefined. Here we have utilized extreme hypoxia (0.5% O2) and concurrent treatment with metal carcinogen (nickel) to evaluate the passage‐dependent response of hMSCs toward cancerous transformation. Effects of hypoxia and nickel treatment on hMSC proliferation, apoptosis, gene and protein expression, replicative senescence, reactive oxygen species (ROS), redox mechanisms, and in vivo tumor growth were analyzed. The behavior of late passage hMSCs in a carcinogenic hypoxia environment follows a profile similar to that of transformed cancer cells (i.e., increased expression of oncogenic proteins, decreased expression of tumor suppressor protein, increased proliferation, decreased apoptosis, and aberrant redox mechanisms), but this effect was not observed in earlier passage control cells. These events resulted in accumulated intracellular ROS in vitro and excessive proliferation in vivo. We suggest a mechanism by which carcinogenic hypoxia modulates the activity of three critical transcription factors (c‐MYC, p53, and HIF1), resulting in accumulated ROS and causing hMSCs to undergo cancer‐like behavioral changes. This is the first study to utilize carcinogenic hypoxia as an environmentally relevant experimental model for studying the age‐dependent cancerous transformation of hMSCs.— Crowder, S. W., Horton, L. W., Lee, H. H., McClain, C. M., Hawkins, O. E., Palmer, A. M. Bae, H., Richmond, A., Sung, H.‐J. Passage‐dependent cancerous transformation of human mesenchymal stem cells under carcinogenic hypoxia. FASEB J. 27, 2788‐2798 (2013). www.fasebj.org

Myeloid IKKβ Promotes Antitumor Immunity by Modulating CCL11 and the Innate Immune Response

Myeloid cells are capable of promoting or eradicating tumor cells and the nodal functions that contribute to their different roles are still obscure. Here, we show that mice with myeloid-specific genetic loss of the NF-κB pathway regulatory kinase IKKβ exhibit more rapid growth of cutaneous and lung melanoma tumors. In a BRAF(V600E/PTEN(-/-)) allograft model, IKKβ loss in macrophages reduced recruitment of myeloid cells into the tumor, lowered expression of MHC class II molecules, and enhanced production of the chemokine CCL11, thereby negatively regulating dendritic-cell maturation. Elevated serum and tissue levels of CCL11 mediated suppression of dendritic-cell differentiation/maturation within the tumor microenvironment, skewing it toward a Th2 immune response and impairing CD8(+) T cell-mediated tumor cell lysis. Depleting macrophages or CD8(+) T cells in mice with wild-type IKKβ myeloid cells enhanced tumor growth, where the myeloid cell response was used to mediate antitumor immunity against melanoma tumors (with less dependency on a CD8(+) T-cell response). In contrast, myeloid cells deficient in IKKβ were compromised in tumor cell lysis, based on their reduced ability to phagocytize and digest tumor cells. Thus, mice with continuous IKKβ signaling in myeloid-lineage cells (IKKβ(CA)) exhibited enhanced antitumor immunity and reduced melanoma outgrowth. Collectively, our results illuminate new mechanisms through which NF-κB signaling in myeloid cells promotes innate tumor surveillance.

Ikk4a/Arf Inactivation with Activation of the NF-κB/IL-6 Pathway Is Sufficient to Drive the Development and Growth of Angiosarcoma

Although human angiosarcoma has been associated frequently with mutational inactivation of the tumor suppressor gene Ink4a/Arf, the underlying mechanisms have not been delineated. Here we report that malignant angiosarcoma is associated with high levels of RelA/NF-κB and IL-6 in contrast to normal vessels or benign hemagiomas. Studies of Ink4a/Arf deficient mice not only recapitulate genetic traits observed in human angiosarcoma, but also unveil a possible therapeutic link comprised of the NF-kB/IL-6/Stat3 signaling axis. In Ink4a/Arf(-/-) cells, NF-κB controlled Stat3 signaling by transcriptionally controlling the expression of IL-6, gp130, and Jak2. Further, IL-6 mediated Stat3 signaling through the sIL-6R. Inhibition of Ikkβ solely in myeloid cells was insufficient to block angiosarcoma development; in contrast, systemic inhibition of Ikkβ, IL-6, or Stat3 markedly inhibited angiosarcoma growth. Our findings offer clinical implications for targeting the NF-kB/IL-6/STAT3 pathway as a rational strategy to treat angiosarcoma.

TCR-like Biomolecules Target Peptide/MHC Class I Complexes on the Surface of Infected and Cancerous Cells

The human leukocyte antigen (HLA; also called major histocompatibility, or MHC) class I system presents peptides that distinguish healthy from diseased cells. Therefore, the discovery of peptide/MHC class I markers can provide highly specific targets for immunotherapy. Over the course of almost two decades, various strategies have been used, with mixed success, to produce antibodies that have recognition specificity for unique peptide/MHC class I complexes that mark infected and cancerous cells. Using these antibody reagents, novel peptide/MHC class I targets have been directly validated on diseased cells and new insight has been gained into the mechanisms of antigen presentation. More recently, these antibodies have shown promise for clinical applications such as therapeutic targeting of cancerous and infected cells and diagnosis and imaging of diseased cells. In this review, the authors comprehensively describe the methods used to identify disease-specific peptide/MHC class I epitopes and generate antibodies to these markers. Finally, they offer several examples that illustrate the promise of using these antibodies as anti-cancer agents.

The dynamic yin-yang interaction of CXCR4 and CXCR7 in breast cancer metastasis

The contribution of CXCR7 to the tumor microenvironment has introduced a new level of complexity to CXCL12 signaling in breast cancer. In the previous issue of Breast Cancer Research, Hernandez and colleagues delineate the roles of CXCR4 and CXCR7 in tumor invasion and metastasis. The authors demonstrate that co-expression of CXCR7 and CXCR4 results in inhibition of CXCL12-mediated invasion, reduced intravasation of tumor cells into the vasculature, and fewer lung metastases compared with parental tumors. The results of this study suggest the combination of small molecule inhibitors of CXCR4 and CXCR7 could dramatically reduce invasion, intravasation, and metastasis and could be highly beneficial for the treatment of invasive breast cancer.

Adaptor protein2 (AP2) orchestrates CXCR2-mediated cell migration.

The chemokine receptor CXCR2 is vital for inflammation, wound healing, angiogenesis, cancer progression and metastasis. Adaptor protein 2 (AP2), a clathrin binding heterotetrameric protein comprised of α, β2, μ2 and σ2 subunits, facilitates clathrin‐mediated endocytosis. Mutation of the LLKIL motif in the CXCR2 carboxyl‐terminal domain (CTD) results in loss of AP2 binding to the receptor and loss of ligand‐mediated receptor internalization and chemotaxis. AP2 knockdown also results in diminished ligand‐mediated CXCR2 internalization, polarization and chemotaxis. Using knockdown/rescue approaches with AP2‐μ2 mutants, the binding domains were characterized in reference to CXCR2 internalization and chemotaxis. When in an open conformation, μ2 Patch 1 and Patch 2 domains bind tightly to membrane PIP2 phospholipids. When AP2‐μ2, is replaced with μ2 mutated in Patch 1 and/or Patch 2 domains, ligand‐mediated receptor binding and internalization are not lost. However, chemotaxis requires AP2‐μ2 Patch 1, but not Patch 2. AP2‐σ2 has been demonstrated to bind dileucine motifs to facilitate internalization. Expression of AP2‐σ2 V88D and V98S dominant negative mutants resulted in loss of CXCR2 mediated chemotaxis. Thus, AP2 binding to both membrane phosphatidylinositol phospholipids and dileucine motifs is crucial for directional migration or chemotaxis. Moreover, AP2‐mediated receptor internalization can be dissociated from AP2‐mediated chemotaxis.

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. Clin Cancer Res; 21(23); 5338–48. ©2015 AACR.