Prostate Cancer Progression Relies on the Mitotic Kinase Citron Kinase.

Prostate cancer remains the second leading cause of cancer death in men in Western cultures. A deeper understanding of the mechanisms by which prostate cancer cells divide to support tumor growth could help devise strategies to overcome treatment resistance and improve survival. Here, we identified that the mitotic AGC family protein kinase citron kinase (CIT) is a pivotal regulator of prostate cancer growth that mediates prostate cancer cell interphase progression. Increased CIT expression correlated with prostate cancer growth induction and aggressive prostate cancer progression, and CIT was overexpressed in prostate cancer compared with benign prostate tissue. CIT overexpression was controlled by an E2F2-Skp2-p27 signaling axis and conferred resistance to androgen-targeted treatment strategies. The effects of CIT relied entirely on its kinase activity. Conversely, CIT silencing inhibited the growth of cell lines and xenografts representing different stages of prostate cancer progression and treatment resistance but did not affect benign epithelial prostate cells or nonprostatic normal cells, indicating a potential therapeutic window for CIT inhibition. CIT kinase activity was identified as druggable and was potently inhibited by the multikinase inhibitor OTS-167, which decreased the proliferation of treatment-resistant prostate cancer cells and patient-derived organoids. Isolation of the in vivo CIT substrates identified proteins involved in diverse cellular functions ranging from proliferation to alternative splicing events that are enriched in treatment-resistant prostate cancer. These findings provide insights into the regulation of aggressive prostate cancer cell behavior by CIT and identify CIT as a functionally diverse and druggable driver of prostate cancer progression. SIGNIFICANCE: The poorly characterized protein kinase citron kinase is a therapeutic target in prostate cancer that drives tumor growth by regulating diverse substrates, which control several hallmarks of aggressive prostate cancer progression. See related commentary by Mishra et al., p. 4008.

A comprehensive analysis of coregulator recruitment, androgen receptor function and gene expression in prostate cancer.

Standard treatment for metastatic prostate cancer (CaP) prevents ligand-activation of androgen receptor (AR). Despite initial remission, CaP progresses while relying on AR. AR transcriptional output controls CaP behavior and is an alternative therapeutic target, but its molecular regulation is poorly understood. Here, we show that action of activated AR partitions into fractions that are controlled preferentially by different coregulators. In a 452-AR-target gene panel, each of 18 clinically relevant coregulators mediates androgen-responsiveness of 0-57% genes and acts as a coactivator or corepressor in a gene-specific manner. Selectivity in coregulator-dependent AR action is reflected in differential AR binding site composition and involvement with CaP biology and progression. Isolation of a novel transcriptional mechanism in which WDR77 unites the actions of AR and p53, the major genomic drivers of lethal CaP, to control cell cycle progression provides proof-of-principle for treatment via selective interference with AR action by exploiting AR dependence on coregulators.

Curcumin Induces Pancreatic Adenocarcinoma Cell Death Via Reduction of the Inhibitors of Apoptosis.

OBJECTIVES: The inhibitor of apoptosis (IAP) proteins are critical modulators of chemotherapeutic resistance in various cancers. To address the alarming emergence of chemotherapeutic resistance in pancreatic cancer, we investigated the efficacy of the turmeric derivative curcumin in reducing IAP protein and mRNA expression resulting in pancreatic cancer cell death. METHODS: The pancreatic adenocarcinoma cell line PANC-1 was used to assess curcumin's effects in pancreatic cancer. Curcumin uptake was measured by spectral analysis and fluorescence microscopy. AlamarBlue and Trypan blue exclusion assays were used to determine PANC-1 cell viability after curcumin treatment. Visualization of PANC-1 cell death was performed using Hoffman Modulation Contrast microscopy. Western blot, and polymerase chain reaction analyses were used to evaluate curcumin's effects on IAP protein and mRNA expression. RESULTS: Curcumin enters PANC-1 cells and is ubiquitously present within the cell after treatment. Furthermore, curcumin reduces cell viability and induces morphological changes characteristic of cell death. Additionally, curcumin decreases IAP protein and mRNA expression in PANC-1 cells. CONCLUSIONS: These data demonstrate that PANC-1 cells are sensitive to curcumin treatment. Futthermore, curcumin is a potential therapeutic tool for overcoming chemotherapeutic resistance mediated by IAPs. Together, this data supports a role for curcumin as part of the therapeutic approach for the treatment of pancreatic cancer.

Localization and upregulation of survivin in cancer health disparities: a clinical perspective.

Survivin is one of the most important members of the inhibitors of apoptosis protein family, as it is expressed in most human cancers but is absent in normal, differentiated tissues. Lending to its importance, survivin has proven associations with apoptosis and cell cycle control, and has more recently been shown to modulate the tumor microenvironment and immune evasion as a result of its extracellular localization. Upregulation of survivin has been found in many cancers including breast, prostate, pancreatic, and hematological malignancies, and it may prove to be associated with the advanced presentation, poorer prognosis, and lower survival rates observed in ethnically diverse populations.

Exosomes Secreted from Human Cancer Cell Lines Contain Inhibitors of Apoptosis (IAP).

Exosomes are endosomal-derived nanovesicles released by normal and tumor cells which have been shown to transfer functionally active protein, lipids, mRNAs and miRNAs between cells. Varying in molecular profiles, biological roles, functional roles and protein contents, exosomes have been described as "multi-purpose carriers" playing a role in supporting the survival and growth of tumor cells. The IAP Survivin has been found to be present in tumor exosomes. However, the existence of other IAPs in tumor exosomes is still unknown. Survivin, cIAP1, cIAP2 and XIAP mRNA and protein are differently expressed in a panel of tumor cell lines: DLCL2, HeLa, MCF-7, Panc-1, and PC3. Exosomes were isolated from conditioned media collected from the cells from which RNA and protein were extracted. Our results provide evidence that like Survivin, XIAP, cIAP1 and cIAP2 proteins are found in tumor exosomes. The mRNA expression, however, is differentially expressed across the tumor cell lines. The presence of these bioactive molecules in exosomes may not only serve as warning signals, but also play a role in providing protection to the cancer cells against changes that are constantly occurring in the tumor microenvironment.

Antimetabolite Treatment for Pancreatic Cancer.

Pancreatic cancer is a deadly and aggressive disease. Less than 1% of diagnosed patients survive 5 years with an average survival time of only 4-8 months. The only option for metastatic pancreatic cancer is chemotherapy where only the antimetabolites gemcitabine and 5-fluorouracil are used clinically. Unfortunately, efforts to improve chemotherapy regimens by combining, 5-fluorouracil or gemcitabine with other drugs, such as cisplatin or oxaliplatin, have not increased cell killing or improved patient survival. The novel antimetabolite zebularine shows promise, inducing apoptosis and arresting cellular growth in various pancreatic cancer cell lines. However, resistance to these antimetabolites remains a problem highlighting the need to discover and develop new antimetabolites that will improve a patient's overall survival.

Tumor-released survivin induces a type-2 t cell response and decreases cytotoxic T cell function, in vitro.

Clinical studies of T cell profiles from cancer patients have shown a skewing toward a type-2 T cell response with decreased cytotoxic T cell function. However, the primary cause of this shift remains unknown. Here we show that tumor-released Survivin, an inhibitor of apoptosis (IAP) protein and tumor-specific antigen, is taken up by T cells and alters their response. The addition of Survivin to T cell cultures resulted in decreased T cell proliferation and reduced cytotoxic CD8(+) T cell function. Additionally, type 1 cell numbers and IFN-γ and IL-2 production were significantly reduced, while IL-4 release and type 2 T cell numbers increased. In contrast, the function and numbers of Th17 and T regulatory cells were not affected. These studies show that tumor-released Survivin modulates T cells resulting in a phenotype similar to that observed in cancer patients with a polarity shift from a type 1 to a type 2 response.

Plasma-derived exosomal survivin, a plausible biomarker for early detection of prostate cancer.

BACKGROUND: Survivin is expressed in prostate cancer (PCa), and its downregulation sensitizes PCa cells to chemotherapeutic agents in vitro and in vivo. Small membrane-bound vesicles called exosomes, secreted from the endosomal membrane compartment, contain RNA and protein that they readily transport via exosome internalization into recipient cells. Recent progress has shown that tumor-derived exosomes play multiple roles in tumor growth and metastasis and may produce these functions via immune escape, tumor invasion and angiogenesis. Furthermore, exosome analysis may provide novel biomarkers to diagnose or monitor PCa treatment. METHODS: Exosomes were purified from the plasma and serum from 39 PCa patients, 20 BPH patients, 8 prostate cancer recurrent and 16 healthy controls using ultracentrifugation and their quantities and qualities were quantified and visualized from both the plasma and the purified exosomes using ELISA and Western blotting, respectively. RESULTS: Survivin was significantly increased in the tumor-derived samples, compared to those from BPH and controls with virtually no difference in the quantity of Survivin detected in exosomes collected from newly diagnosed patients exhibiting low (six) or high (nine) Gleason scores. Exosome Survivin levels were also higher in patients that had relapsed on chemotherapy compared to controls. CONCLUSIONS: These studies demonstrate that Survivin exists in plasma exosomes from both normal, BPH and PCa subjects. The relative amounts of exosomal Survivin in PCa plasma was significantly higher than in those with pre-inflammatory BPH and control plasma. This differential expression of exosomal Survivin was seen with both newly diagnosed and advanced PCa subjects with high or low-grade cancers. Analysis of plasma exosomal Survivin levels may offer a convenient tool for diagnosing or monitoring PCa and may, as it is elevated in low as well as high Gleason scored samples, be used for early detection.