Use of irinotecan for treatment of small cell carcinoma of the prostate

Modeling Androgen Deprivation Therapy-Induced Prostate Cancer Dormancy and Its Clinical Implications

Treatment-induced tumor dormancy is a state in cancer progression where residual disease is present but remains asymptomatic. Dormant cancer cells are treatment-resistant and responsible for cancer recurrence and metastasis. Prostate cancer treated with androgen-deprivation therapy (ADT) often enters a dormant state. ADT-induced prostate cancer dormancy remains poorly understood due to the challenge in acquiring clinical dormant prostate cancer cells and the lack of representative models. In this study, we aimed to develop clinically relevant models for studying ADT-induced prostate cancer dormancy. Dormant prostate cancer models were established by castrating mice bearing patient-derived xenografts (PDX) of hormonal naïve or sensitive prostate cancer. Dormancy status and tumor relapse were monitored and evaluated. Paired pre- and postcastration (dormant) PDX tissues were subjected to morphologic and transcriptome profiling analyses. As a result, we established eleven ADT-induced dormant prostate cancer models that closely mimicked the clinical courses of ADT-treated prostate cancer. We identified two ADT-induced dormancy subtypes that differed in morphology, gene expression, and relapse rates. We discovered transcriptomic differences in precastration PDXs that predisposed the dormancy response to ADT. We further developed a dormancy subtype-based, predisposed gene signature that was significantly associated with ADT response in hormonal naïve prostate cancer and clinical outcome in castration-resistant prostate cancer treated with ADT or androgen-receptor pathway inhibitors.

IMPLICATIONS

We have established highly clinically relevant PDXs of ADT-induced dormant prostate cancer and identified two dormancy subtypes, leading to the development of a novel predicative gene signature that allows robust risk stratification of patients with prostate cancer to ADT or androgen-receptor pathway inhibitors.

Development of patient-derived xenograft models of prostate cancer for maintaining tumor heterogeneity

Prostate cancer (Pca) is a heterogeneous disease with multiple morphological patterns. Thus, the establishment of a patient-derived xenograft (PDX) model that retains key features of the primary tumor is of great significance. This review demonstrates the characteristics and advantages of the Pca PDX model and summarizes the main factors affecting the establishment of the model. Because this model well recapitulates the diverse heterogeneity observed in the clinic, it was extensively utilized to discover new therapeutic targets, screen drugs, and explore metastatic mechanisms. In the future, clinical phenotype and different stages of the Pca patient might be faithfully reflected by PDX model, which provides tremendous potential for understanding Pca biology and achieving individualized treatment.

Encapsulation and Enhanced Delivery of Topoisomerase I Inhibitors in Functionalized Carbon Nanotubes

The topoisomerase I inhibitors SN-38 and camptothecin (CPT) have shown potent anticancer activity, but water insolubility and metabolic instability limits their clinical application. Utilizing carbon nanotubes as a protective shell for water-insoluble SN-38 and CPT while maintaining compatibility with aqueous media via a carboxylic acid-functionalized surface can thus be a strategy to overcome this limitation. Through hydrophobic-hydrophobic interactions, SN-38 and CPT were successfully encapsulated in carboxylic acid functionalized single-walled carbon nanotubes and dispersed in water. The resulting cell proliferation inhibition and drug distribution profile inside the cells suggest that these drug-encapsulated carbon nanotubes can serve as a promising delivery strategy for water-insoluble anticancer drugs.

Patient-derived xenografts: A platform for accelerating translational research in prostate cancer

Recently, there has been renewed interest in the development and characterization of patient-derived tumour xenograft (PDX) models. Numerous PDX models have been established for prostate cancer and, importantly, retain the principal molecular, genetic, and histological characteristics of the donor tumour. As such, these models provide significant improvements over standard cell line xenograft models for biological studies, preclinical drug development, and personalized medicine strategies. This review summarizes the current state of the art in this field, illustrating the opportunities and limitations of PDX models in translational prostate cancer research.

Genitourinary small cell malignancies: prostate and bladder

Small cell carcinoma is an aggressive malignancy often associated with dismal prognosis due to the presence of advanced disease. Small cell malignancies, initially described in the lung (small cell carcinoma of the lung), can occur in extrapulmonary sites, such as prostate (small cell carcinoma of the prostate) and bladder (small cell carcinoma of the bladder), with similar clinicopathologic outcomes. There has been a paradigm shift in the management of small cell carcinoma of the lung from initial surgical treatment to use of chemotherapy followed by local therapies. Such treatment modalities have been applied to small cell carcinoma of the prostate and the bladder, with promise in improving patient survival. Use of platinum-based combination chemotherapy followed by surgical resection and/or radiation offers the most benefit. Further investigation at the molecular level may offer targeted therapies earlier in the course of the disease.

Subrenal capsule grafting technology in human cancer modeling and translational cancer research

Patient-derived xenograft (PDX) cancer models with high fidelity are in great demand. While the majority of PDXs are grafted under the skin of immunodeficient mice, the Living Tumor Laboratory (LTL), using unique subrenal capsule grafting techniques, has successfully established more than 200 transplantable PDX models of various low to high grade human cancers. The LTL PDX models retain key biological properties of the original malignancies, including histopathological and molecular characteristics, tumor heterogeneity, metastatic ability, and response to treatment. The PDXs are stored frozen at early transplant generations in a resurrectable form, which eliminates continuous passaging in mice, thus ensuring maintenance of the high biologic and molecular fidelity and reproducibility of the models. The PDX models have been demonstrated to be powerful tools for (i) studies of cancer progression, metastasis and drug resistance, (ii) evidenced-based precision cancer therapy, (iii) preclinical drug efficacy testing and discovery of new anti-cancer drug candidates. To better provide resources for the research community, an LTL website (www.livingtumorlab.com) has been designed as a publicly accessible database which allows researchers to identify PDX models suitable for translational/preclinical cancer research. In summary, subrenal capsule grafting technology maximizes both tumor engraftment rate and retention of human cancer heterogeneity. Moreover, the method makes possible the recovery of PDXs from frozen stocks for further applications, thus providing a powerful platform for translational cancer research.

Prostate cancer metastasis-driving genes: hurdles and potential approaches in their identification

Metastatic prostate cancer is currently incurable. Metastasis is thought to result from changes in the expression of specific metastasis-driving genes in nonmetastatic prostate cancer tissue, leading to a cascade of activated downstream genes that set the metastatic process in motion. Such genes could potentially serve as effective therapeutic targets for improved management of the disease. They could be identified by comparative analysis of gene expression profiles of patient-derived metastatic and nonmetastatic prostate cancer tissues to pinpoint genes showing altered expression, followed by determining whether silencing of such genes can lead to inhibition of metastatic properties. Various hurdles encountered in this approach are discussed, including (i) the need for clinically relevant, nonmetastatic and metastatic prostate cancer tissues such as xenografts of patients’ prostate cancers developed via subrenal capsule grafting technology and (ii) limitations in the currently available methodology for identification of master regulatory genes.

GATA2 as a potential metastasis-driving gene in prostate cancer

Effective treatment for metastatic prostate cancer is critically needed. The present study was aimed at identifying metastasis-driving genes as potential targets for therapy (oncotargets). A differential gene expression profile of metastatic LTL-313H and non-metastatic LTL-313B prostate cancer tissue xenografts, derived from one patient's specimen, was subjected to integrative analysis using the Ingenuity Upstream Regulator Analysis tool. Six candidate master regulatory genes were identified, including GATA2, a gene encoding a pioneer factor, a special transcription factor facilitating the recruitment of additional transcription factors. Elevated GATA2 expression in metastatic prostate cancer tissues correlated with poor patient prognosis. Furthermore, GATA2 gene silencing in human prostate cancer LNCaP cells led to a marked reduction in cell migration, tissue invasion, focal adhesion disassembly and to a dramatic change in cell transcriptomes, indicating that GATA2 plays a critical role in prostate cancer metastasis. As such, GATA2 could represent a prostate cancer metastasis-driving gene and a potential target for therapy of metastatic prostate cancer.

Next generation patient-derived prostate cancer xenograft models

There is a critical need for more effective therapeutic approaches for prostate cancer. Research in this area, however, has been seriously hampered by a lack of clinically relevant, experimental in vivo models of the disease. This review particularly focuses on the development of prostate cancer xenograft models based on subrenal capsule grafting of patients’ tumor tissue into nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. This technique allows successful development of transplantable, patient-derived cancer tissue xenograft lines not only from aggressive metastatic, but also from localized prostate cancer tissues. The xenografts have been found to retain key biological properties of the original malignancies, including histopathological and molecular characteristics, tumor heterogeneity, response to androgen ablation and metastatic ability. As such, they are highly clinically relevant and provide valuable tools for studies of prostate cancer progression at cellular and molecular levels, drug screening for personalized cancer therapy and preclinical drug efficacy testing; especially when a panel of models is used to cover a broader spectrum of the disease. These xenograft models could therefore be viewed as next-generation models of prostate cancer.

Ubiquitin‑specific protease 22‑induced autophagy is correlated with poor prognosis of pancreatic cancer

Ubiquitin‑specific protease 22 (USP22) is a component of the transcription regulatory histone acetylation complex SAGA, which broadly regulates gene transcription and correlates with cancer progression, metastasis and prognosis. Autophagy is a cell pathway with dual functions that promotes cell survival or death. However, it is not known whether USP22 can regulate autophagy in pancreatic cancer. In the present study, we first identified that USP22 was overexpressed in a large number of pancreatic cancer patient samples, concomitant with the increased expression of LC3, a marker of autophagy. Statistical analysis revealed that the increase in USP22 and autophagy was positively correlated with poor prognosis of pancreatic cancer patients. Further investigation using a human pancreatic cancer cell (Panc‑1) identified that the overexpression of USP22 increased the processing of LC3 into the active form LC3‑II and the number of autophagosomes, thus leading to enhanced autophagy. Activation of ERK1/2 kinase rather than AKT1 by USP22 was found to be one of the mechanisms promoting LC3 processing. USP22‑induced autophagy was also found to enhance cell proliferation and resistance to starvation and chemotherapeutic drugs in Panc‑1 cells, therefore expressing an overall effect that promotes cell survival. Collectively, the present study demonstrated a new function of USP22 that induces autophagy, thus leading to the poor prognosis of pancreatic cancer.

Autophagy, Warburg, and Warburg reverse effects in human cancer

Autophagy is a highly regulated-cell pathway for degrading long-lived proteins as well as for clearing cytoplasmic organelles. Autophagy is a key contributor to cellular homeostasis and metabolism. Warburg hypothesized that cancer growth is frequently associated with a deviation of a set of energy generation mechanisms to a nonoxidative breakdown of glucose. This cellular phenomenon seems to rely on a respiratory impairment, linked to mitochondrial dysfunction. This mitochondrial dysfunction results in a switch to anaerobic glycolysis. It has been recently suggested that epithelial cancer cells may induce the Warburg effect in neighboring stromal fibroblasts in which autophagy was activated. These series of observations drove to the proposal of a putative reverse Warburg effect of pathophysiological relevance for, at least, some tumor phenotypes. In this review we introduce the autophagy process and its regulation and its selective pathways and role in cancer cell metabolism. We define and describe the Warburg effect and the newly suggested "reverse" hypothesis. We also discuss the potential value of modulating autophagy with several pharmacological agents able to modify the Warburg effect. The association of the Warburg effect in cancer and stromal cells to tumor-related autophagy may be of relevance for further development of experimental therapeutics as well as for cancer prevention.

Enhanced anticancer activity of a combination of docetaxel and Aneustat (OMN54) in a patient-derived, advanced prostate cancer tissue xenograft model

The current first‐line treatment for advanced metastatic prostate cancer, i.e. docetaxel‐based therapy, is only marginally effective. The aim of the present study was to determine whether such therapy can be improved by combining docetaxel with Aneustat (OMN54), a multivalent botanical drug candidate shown to have anti‐prostate cancer activity in preliminary in vitro experiments, which is currently undergoing a Phase‐I Clinical Trial. Human metastatic, androgen‐independent C4‐2 prostate cancer cells and NOD‐SCID mice bearing PTEN‐deficient, metastatic and PSA‐secreting, patient‐derived subrenal capsule LTL‐313H prostate cancer tissue xenografts were treated with docetaxel and Aneustat, alone and in combination. In vitro, Aneustat markedly inhibited C4‐2 cell replication in a dose‐dependent manner. When Aneustat was combined with docetaxel, the growth inhibitions of the drugs were essentially additive. In vivo, however, the combination of docetaxel and Aneustat enhanced anti‐tumor activity synergistically and very markedly, without inducing major host toxicity. Complete growth inhibition and shrinkage of the xenografts could be obtained with the combined drugs as distinct from the drugs on their own. Analysis of the gene expression of the xenografts using microarray indicated that docetaxel + Aneustat led to expanded anticancer activity, in particular to targeting of cancer hallmarks that were not affected by the single drugs. Our findings, obtained with a highly clinically relevant prostate cancer model, suggest, for the first time, that docetaxel‐based therapy of advanced human prostate cancer may be improved by combining docetaxel with Aneustat.

First‐line, docetaxel‐based therapy of advanced prostate cancer is only marginally effective.

The efficacy of docetaxel combined with Aneustat was determined in a metastatic xenograft model.

Anti‐tumor activity was synergistically and markedly enhanced without major host toxicity.

Gene expression analysis indicated docetaxel + Aneustat led to expanded anticancer activity.

Docetaxel‐based therapy of advanced prostate cancer may be improved by combining docetaxel with Aneustat.

Molecular characterization of neuroendocrine prostate cancer and identification of new drug targets

Neuroendocrine prostate cancer (NEPC) is an aggressive subtype of prostate cancer that most commonly evolves from preexisting prostate adenocarcinoma (PCA). Using Next Generation RNA-sequencing and oligonucleotide arrays, we profiled 7 NEPC, 30 PCA, and 5 benign prostate tissue (BEN), and validated findings on tumors from a large cohort of patients (37 NEPC, 169 PCA, 22 BEN) using IHC and FISH. We discovered significant overexpression and gene amplification of AURKA and MYCN in 40% of NEPC and 5% of PCA, respectively, and evidence that that they cooperate to induce a neuroendocrine phenotype in prostate cells. There was dramatic and enhanced sensitivity of NEPC (and MYCN overexpressing PCA) to Aurora kinase inhibitor therapy both in vitro and in vivo, with complete suppression of neuroendocrine marker expression following treatment. We propose that alterations in Aurora kinase A and N-myc are involved in the development of NEPC, and future clinical trials will help determine from the efficacy of Aurora kinase inhibitor therapy.

SIGNIFICANCE

We report on the largest in-depth molecular analysis of NEPC and provide new insight into molecular events involved in the progression of prostate cancer.

From sequence to molecular pathology, and a mechanism driving the neuroendocrine phenotype in prostate cancer

The current paradigm of cancer care relies on predictive nomograms which integrate detailed histopathology with clinical data. However, when predictions fail, the consequences for patients are often catastrophic, especially in prostate cancer where nomograms influence the decision to therapeutically intervene. We hypothesized that the high dimensional data afforded by massively parallel sequencing (MPS) is not only capable of providing biological insights, but may aid molecular pathology of prostate tumours. We assembled a cohort of six patients with high-risk disease, and performed deep RNA and shallow DNA sequencing in primary tumours and matched metastases where available. Our analysis identified copy number abnormalities, accurately profiled gene expression levels, and detected both differential splicing and expressed fusion genes. We revealed occult and potentially dormant metastases, unambiguously supporting the patients' clinical history, and implicated the REST transcriptional complex in the development of neuroendocrine prostate cancer, validating this finding in a large independent cohort. We massively expand on the number of novel fusion genes described in prostate cancer; provide fresh evidence for the growing link between fusion gene aetiology and gene expression profiles; and show the utility of fusion genes for molecular pathology. Finally, we identified chromothripsis in a patient with chronic prostatitis. Our results provide a strong foundation for further development of MPS-based molecular pathology.

Next generation sequencing of prostate cancer from a patient identifies a deficiency of methylthioadenosine phosphorylase, an exploitable tumor target

Castrate-resistant prostate cancer (CRPC) and neuroendocrine carcinoma of the prostate are invariably fatal diseases for which only palliative therapies exist. As part of a prostate tumor sequencing program, a patient tumor was analyzed using Illumina genome sequencing and a matched renal capsule tumor xenograft was generated. Both tumor and xenograft had a homozygous 9p21 deletion spanning the MTAP, CDKN2, and ARF genes. It is rare for this deletion to occur in primary prostate tumors, yet approximately 10% express decreased levels of methylthioadenosine phosphorylase (MTAP) mRNA. Decreased MTAP expression is a prognosticator for poor outcome. Moreover, it seems that this deletion is more common in CRPC than in primary prostate cancer. We show for the first time that treatment with methylthioadenosine and high dose 6-thioguanine causes marked inhibition of a patient-derived neuroendocrine xenograft growth while protecting the host from 6-thioguanine toxicity. This therapeutic approach can be applied to other MTAP-deficient human cancers as deletion or hypermethylation of the MTAP gene occurs in a broad spectrum of tumors at high frequency. The combination of genome sequencing and patient-derived xenografts can identify candidate therapeutic agents and evaluate them for personalized oncology.

Chemotherapy and autophagy-mediated cell death in pancreatic cancer cells

Autophagy is an evolutionarily preserved degradation process of cytoplasmic cellular constituents and plays important physiological roles in human health and disease. It has been proposed that autophagy plays an important role both in tumor progression and in promotion of cancer cell death, although the molecular mechanisms responsible for this dual action of autophagy in cancer have not been elucidated. Pancreatic ductal adenocarcinoma is one of the most aggressive human malignancies with 2-3% five-year survival rate. Its poor prognosis has been attributed to the lack of specific symptoms and early detection tools, and its relatively refractory to traditional cytotoxic agents and radiotherapy. Experimental evidence pointed at autophagy as a pancreatic cancer cell mechanism to survive under adverse environmental conditions, or as a defective programmed cell death mechanism that favors pancreatic cancer cell resistance to treatment. Here, we consider several phenotypical alterations that have been related to increase or decrease the autophagic process in pancreatic tumor cells. We specially review autophagy as a cell death mechanism in response to chemotherapeutic drugs.