Juliano D. Paccez

The receptor tyrosine kinase Axl is an essential regulator of prostate cancer proliferation and tumor growth and represents a new therapeutic target

Deregulation of the receptor tyrosine kinase Axl has been implicated in the progression of several human cancers. However, the role of Axl in prostate cancer remains poorly understood, and the therapeutic efficacy of Axl targeting remains untested. In this report we identified Axl as a new therapeutic target for prostate cancer. Axl is consistently overexpressed in prostate cancer cell lines and human prostate tumors. Interestingly, the blockage of Axl gene expression strongly inhibits proliferation, migration, invasion and tumor growth. Furthermore, inhibition of Axl expression by small interfering RNA regulates a transcriptional program of genes involved in cell survival, strikingly all connected to the nuclear factor-κB pathway. Additionally, blockage of Axl expression leads to inhibition of Akt, IKKα and IκBα phosphorylation, increasing IκBα expression and stability. Furthermore, induction of Akt phosphorylation by insulin-like growth factor 1 in Axl knockdown cells restores Akt activity and proliferation. Taken together, our results establish an unambiguous role for Axl in prostate cancer tumorigenesis with implications for prostate cancer treatment.

The receptor tyrosine kinase Axl in cancer: Biological functions and therapeutic implications

The receptor tyrosine kinase Axl has been implicated in the malignancy of different types of cancer. Emerging evidence of Axl upregulation in numerous cancers, as well as reports demonstrating that its inhibition blocks tumor formation in animal models, highlight the importance of Axl as a new potential therapeutic target. Furthermore, recent data demonstrate that Axl plays a pivotal role in resistance to chemotherapeutic regimens. In this review we discuss the functions of Axl and its regulation and role in cancer development, resistance to therapy, and its importance as a potential drug target, focusing on acute myeloid leukemia, breast, prostate and non‐small cell lung cancers.

Computational repositioning and preclinical validation of pentamidine for renal cell cancer

Although early stages of clear cell renal cell carcinoma (ccRCC) are curable, survival outcome for metastatic ccRCC remains poor. We previously established a highly accurate signature of differentially expressed genes that distinguish ccRCC from normal kidney. The purpose of this study was to apply a new individualized bioinformatics analysis (IBA) strategy to these transcriptome data in conjunction with Gene Set Enrichment Analysis of the Connectivity Map (C-MAP) database to identify and reposition FDA-approved drugs for anticancer therapy. Here, we demonstrate that one of the drugs predicted to revert the RCC gene signature toward normal kidney, pentamidine, is effective against RCC cells in culture and in a RCC xenograft model. ccRCC-specific gene expression signatures of individual patients were used to query the C-MAP software. Eight drugs with negative correlation and P-value <0.05 were analyzed for efficacy against RCC in vitro and in vivo. Our data demonstrate consistency across most patients with ccRCC for the set of high-scoring drugs. Most of the selected high-scoring drugs potently induce apoptosis in RCC cells. Several drugs also demonstrate selectivity for Von Hippel-Lindau negative RCC cells. Most importantly, at least one of these drugs, pentamidine, slows tumor growth in the 786-O human ccRCC xenograft mouse model. Our findings suggest that pentamidine might be a new therapeutic agent to be combined with current standard-of-care regimens for patients with metastatic ccRCC and support our notion that IBA combined with C-MAP analysis enables repurposing of FDA-approved drugs for potential anti-RCC therapy. Mol Cancer Ther; 13(7); 1929–41. ©2014 AACR.

Adenosine Uptake is the Major Effector of Extracellular ATP Toxicity in Human Cervical Cancer Cells

Cervical cancer cells respond to high extracellular ATP. There is cooperation between ATP and its metabolites with regard to cytotoxicity, with adenosine necessary, but not sufficient, to induce cell death in the whole population of cells, which is significant in the context of cancer therapeutics.

JunD-mediated repression of GADD45α and γ regulates escape from cell death in prostate cancer

The AP-1 transcription factor complex has been implicated in a variety of biological processes including cell differentiation, proliferation, apoptosis and oncogenic transformation. We previously established that activation of the AP-1 family member JunD contributes to deregulated expression of the anti-apoptotic IL-6 gene in prostate cancer cells. We now show that inhibition of JunD in prostate cancer cells results in GADD45α- and γ-dependent induction of cell death and inhibition of tumor growth that is mediated at least partially via c-Jun N-terminal kinase (JNK) and p38 kinase activation. Apoptosis induction by dominant negative JunD and JNK and p38 kinase activation are impeded upon knock down of GADD45α and γ expression by small interfering RNA, most vividly demonstrating the central role of GADD45α and γ in JunD-mediated escape of prostate cancer cells from programmed cell death.

Discovery of novel candidate urinary protein biomarkers for prostate cancer in a multiethnic cohort of South African patients via label-free mass spectrometry

Improvement in diagnostic accuracy of prostate cancer (PCa) progression using MS‐based methods to analyze biomarkers in our African, Caucasian, and Mixed Ancestry patients can advance early detection and treatment monitoring.

Inactivation of GSK3β and activation of NF-κB pathway via Axl represents an important mediator of tumorigenesis in esophageal squamous cell carcinoma.

Deregulation of Axl in esophageal squamous cell carcinoma (OSCC) with potential therapeutic implications is described for the first time. This paper also sheds light on the understanding of how Axl regulates OSCC development in vitro and in vivo. Axl expression leads to an Akt-dependent regulation of glycogen synthase kinase 3β activity and the nucluear factor kappaB (NF-κB) pathway, affecting the epithelial–mesenchymal transition.

GADD45α and γ interaction with CDK11p58 regulates SPDEF protein stability and SPDEF-mediated effects on cancer cell migration

The epithelium-specific Ets transcription factor, SPDEF, plays a critical role in metastasis of prostate and breast cancer cells. While enhanced SPDEF expression blocks migration and invasion, knockdown of SPDEF expression enhances migration, invasion, and metastasis of cancer cells. SPDEF expression and activation is tightly regulated in cancer cells; however, the precise mechanism of SPDEF regulation has not been explored in detail. In this study we provide evidence that the cell cycle kinase CDK11p58, a protein involved in G2/M transition and degradation of several transcription factors, directly interacts with and phosphorylates SPDEF on serine residues, leading to subsequent ubiquitination and degradation of SPDEF through the proteasome pathway. As a consequence of CDK11p58 mediated degradation of SPDEF, this loss of SPDEF protein results in increased prostate cancer cell migration and invasion. In contrast, knockdown of CDK11p58 protein expression by interfering RNA or SPDEF overexpression inhibit migration and invasion of cancer cells. We demonstrate that CDK11p58 mediated degradation of SPDEF is attenuated by Growth Arrest and DNA damage-inducible 45 (GADD45) α and, two proteins inducing G2/M cell cycle arrest. We show that GADD45 α and γ, directly interact with CDK11p58 and thereby inhibit CDK11p58 activity, and consequentially SPDEF phosphorylation and degradation, ultimately reducing prostate cancer cell migration and invasion. Our findings provide new mechanistic insights into the complex regulation of SPDEF activity linked to cancer metastasis and characterize a previously unidentified SPDEF/CDK11p58/GADD45α/γ pathway that controls SPDEF protein stability and SPDEF-mediated effects on cancer cell migration and invasion.

The Dual Role of TAM Receptors in Autoimmune Diseases and Cancer: An Overview

Receptor tyrosine kinases (RTKs) regulate cellular processes by converting signals from the extracellular environment to the cytoplasm and nucleus. Tyro3, Axl, and Mer (TAM) receptors form an RTK family that plays an intricate role in tissue maintenance, phagocytosis, and inflammation as well as cell proliferation, survival, migration, and development. Defects in TAM signaling are associated with numerous autoimmune diseases and different types of cancers. Here, we review the structure of TAM receptors, their ligands, and their biological functions. We discuss the role of TAM receptors and soluble circulating TAM receptors in the autoimmune diseases systemic lupus erythematosus (SLE) and multiple sclerosis (MS). Lastly, we discuss the effect of TAM receptor deregulation in cancer and explore the therapeutic potential of TAM receptors in the treatment of diseases.

Abstract 3053: Receptor tyrosine kinase AXL as a new target for prostate cancer therapy

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Axl is a receptor tyrosine kinase of the family of TAM receptors (which includes TYRO3 and MER) and plays roles in different types of cancer. It is highly expressed in metastatic colon carcinoma, gastric, uterine endometrial and certain types of breast cancer, and sarcoma. As Axl is upregulated in several metastatic cell types it may play a role during invasion and metastasis. Tyrosine kinases (TKs) represent a major class of proto-oncogenes and are involved in tumor growth as well as progression and metastasis of cancer cells. TKs are being actively studied as targets for therapeutic intervention and several of this tyrosine kinase have shown efficacy in clinical trials. Prostate cancer has become the most common solid cancer in older men and is one of the most frequent causes of cancer deaths. Although androgen ablation therapy, surgery and radiation therapy are effective for the treatment of local prostate cancer, there is no effective treatment available for patients with the metastatic androgen-independent disease. In this work we demonstrated the role of Axl in prostate cancer progression. Using real time PCR to access the level of several tyrosine kinase receptors expression in prostate cancer cell and human tissue, we have identified the tyrosine kinase receptor Axl as a potential target for prostate cancer therapy. Axl has consistent overexpression across prostate cancer cell lines and human prostate tumor tissue providing a model for testing the targeting of Axl. Preliminary data shows a significant increase of Axl expression was found in metastatic PCa cells and clinical samples (48% of adenocarcinomas of prostate when compared with normal prostate tissue). Interestingly, microarray analysis in addition to pathway analysis of PCa cells infected with lentivirus encoding siRNA against Axl revealed that some survival pathways are inhibited, but strikingly all members of the NF-κB pathway are down regulated. Furthermore, the blockage of Axl gene expression strongly inhibits proliferation, migration and invasion of PCa cells. Pilot studies in animal models demonstrate that inhibition of Axl reduces dramatically tumor formation. since our xenograft subcutaneous model in MF5 nude mice demonstrate that blockage of Axl reduces tumor formation by 49.5%. Taken together these data demonstrated that Axl plays role for migration, invasion and tumor development and can be used as marker for invasive and metastatic tumors. Our data also indicates that Axl can be used as a target for drug therapies since its inhibition leads to induction of apoptosis and blocks cell proliferation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3053. doi:10.1158/1538-7445.AM2011-3053