Hedgehog overexpression leads to the formation of prostate cancer stem cells with metastatic property irrespective of androgen receptor expression in the mouse model

Targeting SOX4/PCK2 signaling suppresses neuroendocrine trans-differentiation of castration-resistant prostate cancer

BACKGROUND

Neuroendocrine prostate cancer (NEPC), a lethal subset of prostate cancer (PCa), is characterized by loss of AR signaling and resistance to AR-targeted therapy. While it is well reported that second-generation AR blockers induce neuroendocrine (NE) trans-differentiation of castration-resistant prostate cancer (CRPC) to promote the occurrence of NEPC, and pluripotent transcription factors might be potential regulators, the underlying molecular mechanisms remain unclear.

METHODS

We analyzed the data from public databsets to screen candidate genes and then focused on SOX4, a regulator of NE trans-differentiation. The expression changes of SOX4 and its relationship with tumor progression were validated in clinical tumor tissues. We evaluated malignant characteristics related to NEPC in prostate cancer cell lines with stable overexpression or knockdown of SOX4 in vitro. Tumor xenografts were analyzed after inoculating the relevant cell lines into nude mice. RNA-seq, ATAC-seq, non-targeted metabolomics analysis, as well as molecular and biochemical assays were carried out to determine the mechanism.

RESULTS

We screened public datasets and identified that expression of SOX4 was significantly elevated in NEPC. Overexpressing SOX4 in C4-2B cells increased cell proliferation and migration, upregulated the expression of NE marker genes, and inhibited AR expression. Consistently, inhibition of SOX4 expression in DU-145 and PC-3 cells reduced the above malignant phenotypes and repressed the expression of NE marker genes. For the in vivo assay, we found that knockdown of SOX4 inhibited tumor growth of subcutaneous xenografts in castrated nude mice which were concomitantly treated with enzalutamide (ENZ). Mechanically, we identified that one of the key enzymes in gluconeogenesis, PCK2, was a novel target of SOX4. The activation of carbohydrate metabolism reprogramming by SOX4 could promote NE trans-differentiation via the SOX4/PCK2 pathway.

CONCLUSIONS

Our findings reveal that SOX4 promotes NE trans-differentiation both in vitro and in vivo via directly enhancing PCK2 activity to activate carbohydrate metabolism reprogramming. The SOX4/PCK2 pathway and its downstream changes might be novel targets for blocking NE trans-differentiation.

Transcending frontiers in prostate cancer: the role of oncometabolites on epigenetic regulation, CSCs, and tumor microenvironment to identify new therapeutic strategies

Prostate cancer, as one of the most prevalent malignancies in males, exhibits an approximate 5-year survival rate of 95% in advanced stages. A myriad of molecular events and mutations, including the accumulation of oncometabolites, underpin the genesis and progression of this cancer type. Despite growing research demonstrating the pivotal role of oncometabolites in supporting various cancers, including prostate cancer, the root causes of their accumulation, especially in the absence of enzymatic mutations, remain elusive. Consequently, identifying a tangible therapeutic target poses a formidable challenge. In this review, we aim to delve deeper into the implications of oncometabolite accumulation in prostate cancer. We center our focus on the consequential epigenetic alterations and impacts on cancer stem cells, with the ultimate goal of outlining novel therapeutic strategies.

Genomic Profiling of Metastatic Castration-Resistant Prostate Cancer Samples Resistant to Androgen Receptor Pathway Inhibitors

PURPOSE

The androgen receptor axis inhibitors (ARPI; e.g., enzalutamide, abiraterone acetate) are administered in daily practice for men with metastatic castration-resistant prostate cancer (mCRPC). However, not all patients respond, and mechanisms of both primary and acquired resistance remain largely unknown.

EXPERIMENTAL DESIGN

In the prospective trial MATCH-R (NCT02517892), 59 patients with mCRPC underwent whole-exome sequencing (WES) and/or RNA sequencing (RNA-seq) of samples collected before starting ARPI. Also, 18 patients with mCRPC underwent biopsy at time of resistance. The objectives were to identify genomic alterations associated with resistance to ARPIs as well as to describe clonal evolution. Associations of genomic and transcriptomic alterations with primary resistance were determined using Wilcoxon and Fisher exact tests.

RESULTS

WES analysis indicated that no single-gene genomic alterations were strongly associated with primary resistance. RNA-seq analysis showed that androgen receptor (AR) gene alterations and expression levels were similar between responders and nonresponders. RNA-based pathway analysis found that patients with primary resistance had a higher Hedgehog pathway score, a lower AR pathway score and a lower NOTCH pathway score than patients with a response. Subclonal evolution and acquisition of new alterations in AR-related genes or neuroendocrine differentiation are associated with acquired resistance. ARPIs do not induce significant changes in the tumor transcriptome of most patients; however, programs associated with cell proliferation are enriched in resistant samples.

CONCLUSIONS

Low AR activity, activation of stemness programs, and Hedgehog pathway were associated with primary ARPIs' resistance, whereas most acquired resistance was associated with subclonal evolution, AR-related events, and neuroendocrine differentiation. See related commentary by Slovin, p. 4323.

Hedgehog signaling in tissue homeostasis, cancers, and targeted therapies

The past decade has seen significant advances in our understanding of Hedgehog (HH) signaling pathway in various biological events. HH signaling pathway exerts its biological effects through a complex signaling cascade involved with primary cilium. HH signaling pathway has important functions in embryonic development and tissue homeostasis. It plays a central role in the regulation of the proliferation and differentiation of adult stem cells. Importantly, it has become increasingly clear that HH signaling pathway is associated with increased cancer prevalence, malignant progression, poor prognosis and even increased mortality. Understanding the integrative nature of HH signaling pathway has opened up the potential for new therapeutic targets for cancer. A variety of drugs have been developed, including small molecule inhibitors, natural compounds, and long non-coding RNA (LncRNA), some of which are approved for clinical use. This review outlines recent discoveries of HH signaling in tissue homeostasis and cancer and discusses how these advances are paving the way for the development of new biologically based therapies for cancer. Furthermore, we address status quo and limitations of targeted therapies of HH signaling pathway. Insights from this review will help readers understand the function of HH signaling in homeostasis and cancer, as well as opportunities and challenges of therapeutic targets for cancer.

Cancer Stem Cells and Prostate Cancer: A Narrative Review

Cancer stem cells (CSCs) are a small and elusive subpopulation of self-renewing cancer cells with the remarkable ability to initiate, propagate, and spread malignant disease. In the past years, several authors have focused on the possible role of CSCs in PCa development and progression. PCa CSCs typically originate from a luminal prostate cell. Three main pathways are involved in the CSC development, including the Wnt, Sonic Hedgehog, and Notch signaling pathways. Studies have observed an important role for epithelial mesenchymal transition in this process as well as for some specific miRNA. These studies led to the development of studies targeting these specific pathways to improve the management of PCa development and progression. CSCs in prostate cancer represent an actual and promising field of research.

The Molecular Biology of Prostate Cancer Stem Cells: From the Past to the Future

Prostate cancer (PCa) continues to rank as the second leading cause of cancer-related mortality in western countries, despite the golden treatment using androgen deprivation therapy (ADT) or anti-androgen therapy. With decades of research, scientists have gradually realized that the existence of prostate cancer stem cells (PCSCs) successfully explains tumor recurrence, metastasis and therapeutic failure of PCa. Theoretically, eradication of this small population may improve the efficacy of current therapeutic approaches and prolong PCa survival. However, several characteristics of PCSCs make their diminishment extremely challenging: inherent resistance to anti-androgen and chemotherapy treatment, over-activation of the survival pathway, adaptation to tumor micro-environments, escape from immune attack and being easier to metastasize. For this end, a better understanding of PCSC biology at the molecular level will definitely inspire us to develop PCSC targeted approaches. In this review, we comprehensively summarize signaling pathways responsible for homeostatic regulation of PCSCs and discuss how to eliminate these fractional cells in clinical practice. Overall, this study deeply pinpoints PCSC biology at the molecular level and provides us some research perspectives.

State-of-the-art therapeutic strategies for targeting cancer stem cells in prostate cancer

The development of new therapeutic strategies is on the increase for prostate cancer stem cells, owing to current standardized therapies for prostate cancer, including chemotherapy, androgen deprivation therapy (ADT), radiotherapy, and surgery, often failing because of tumor relapse ability. Ultimately, tumor relapse develops into advanced castration-resistant prostate cancer (CRPC), which becomes an irreversible and systemic disease. Hence, early identification of the intracellular components and molecular networks that promote prostate cancer is crucial for disease management and therapeutic intervention. One of the potential therapeutic methods for aggressive prostate cancer is to target prostate cancer stem cells (PCSCs), which appear to be a primary focal point of cancer metastasis and recurrence and are resistant to standardized therapies. PCSCs have also been documented to play a major role in regulating tumorigenesis, sphere formation, and the metastasis ability of prostate cancer with their stemness features. Therefore, the current review highlights the origin and identification of PCSCs and their role in anti-androgen resistance, as well as stemness-related signaling pathways. In addition, the review focuses on the current advanced therapeutic strategies for targeting PCSCs that are helping to prevent prostate cancer initiation and progression, such as microRNAs (miRNAs), nanotechnology, chemotherapy, immunotherapy, the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) gene-editing system, and photothermal ablation (PTA) therapy.

Drug and apoptosis resistance in cancer stem cells: a puzzle with many pieces

Resistance to anticancer agents and apoptosis results in cancer relapse and is associated with cancer mortality. Substantial data have provided convincing evidence establishing that human cancers emerge from cancer stem cells (CSCs), which display self-renewal and are resistant to anticancer drugs, radiation, and apoptosis, and express enhanced epithelial to mesenchymal progression. CSCs represent a heterogeneous tumor cell population and lack specific cellular targets, which makes it a great challenge to target and eradicate them. Similarly, their close relationship with the tumor microenvironment creates greater complexity in developing novel treatment strategies targeting CSCs. Several mechanisms participate in the drug and apoptosis resistance phenotype in CSCs in various cancers. These include enhanced expression of ATP-binding cassette membrane transporters, activation of various cytoprotective and survival signaling pathways, dysregulation of stemness signaling pathways, aberrant DNA repair mechanisms, increased quiescence, autophagy, increased immune evasion, deficiency of mitochondrial-mediated apoptosis, upregulation of anti-apoptotic proteins including c-FLIP [cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein], Bcl-2 family members, inhibitors of apoptosis proteins, and PI3K/AKT signaling. Studying such mechanisms not only provides mechanistic insights into these cells that are unresponsive to drugs, but may lead to the development of targeted and effective therapeutics to eradicate CSCs. Several studies have identified promising strategies to target CSCs. These emerging strategies may help target CSC-associated drug resistance and metastasis in clinical settings. This article will review the CSCs drug and apoptosis resistance mechanisms and how to target CSCs.

Advances in the Current Understanding of the Mechanisms Governing the Acquisition of Castration-Resistant Prostate Cancer

Despite aggressive treatment and androgen-deprivation therapy, most prostate cancer patients ultimately develop castration-resistant prostate cancer (CRPC), which is associated with high mortality rates. However, the mechanisms governing the development of CRPC are poorly understood, and androgen receptor (AR) signaling has been shown to be important in CRPC through AR gene mutations, gene overexpression, co-regulatory factors, AR shear variants, and androgen resynthesis. A growing number of non-AR pathways have also been shown to influence the CRPC progression, including the Wnt and Hh pathways. Moreover, non-coding RNAs have been identified as important regulators of the CRPC pathogenesis. The present review provides an overview of the relevant literature pertaining to the mechanisms governing the molecular acquisition of castration resistance in prostate cancer, providing a foundation for future, targeted therapeutic efforts.

Drug resistance and Cancer stem cells

Therapy resistance is a major problem when treating cancer patients as cancer cells develop mechanisms that counteract the effect of therapeutic compounds, leading to fit and more aggressive clones that contribute to poor prognosis. Therapy resistance can be both intrinsic and/or acquired. These are multifactorial events, and some are related to factors including adaptations in cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), deregulation of key signaling pathways, drug efflux through ABC transporters, acquired mutations, evading apoptosis, and activation of DNA damage response among others. Among these factors, CSCs represent the major source of therapy resistance. CSCs are a subset of tumor cells that are capable of self-renewal and multilineage progenitor expansion that are known to be intrinsically resistant to anticancer treatments. Multiple clones of CSCs pre-exist, and some can adopt and expand easily to changes in the tumor microenvironment (TME) and/or in response to radio- and chemotherapy. A combination of both intrinsic and extrinsic factors contributes to CSC-mediated therapy resistance. In this review, we will focus on CSCs and therapy resistance as well as suggest strategies to eliminate CSCs and, therefore, overcome resistance. Video abstract.

Hedgehog Signaling and Truncated GLI1 in Cancer

The hedgehog (HH) signaling pathway regulates normal cell growth and differentiation. As a consequence of improper control, aberrant HH signaling results in tumorigenesis and supports aggressive phenotypes of human cancers, such as neoplastic transformation, tumor progression, metastasis, and drug resistance. Canonical activation of HH signaling occurs through binding of HH ligands to the transmembrane receptor Patched 1 (PTCH1), which derepresses the transmembrane G protein-coupled receptor Smoothened (SMO). Consequently, the glioma-associated oncogene homolog 1 (GLI1) zinc-finger transcription factors, the terminal effectors of the HH pathway, are released from suppressor of fused (SUFU)-mediated cytoplasmic sequestration, permitting nuclear translocation and activation of target genes. Aberrant activation of this pathway has been implicated in several cancer types, including medulloblastoma, rhabdomyosarcoma, basal cell carcinoma, glioblastoma, and cancers of lung, colon, stomach, pancreas, ovarian, and breast. Therefore, several components of the HH pathway are under investigation for targeted cancer therapy, particularly GLI1 and SMO. GLI1 transcripts are reported to undergo alternative splicing to produce truncated variants: loss-of-function GLI1ΔN and gain-of-function truncated GLI1 (tGLI1). This review covers the biochemical steps necessary for propagation of the HH activating signal and the involvement of aberrant HH signaling in human cancers, with a highlight on the tumor-specific gain-of-function tGLI1 isoform.

The regulatory pathways leading to stem-like cells underlie prostate cancer progression

Prostate cancer (PCa) is the most common cause of malignancy in males and the third leading cause of cancer mortality in the United States. The standard care for primary PCa with local invasive disease mainly is surgery and radiation. For patients with distant metastases, androgen deprivation therapy (ADT) is a gold standard. Regardless of a favorable outcome of ADT, patients inevitably relapse to an end-stage castration-resistant prostate cancer (CRPC) leading to mortality. Therefore, revealing the mechanism and identifying cellular components driving aggressive PCa is critical for prognosis and therapeutic intervention. Cancer stem cell (CSC) phenotypes characterized as poor differentiation, cancer initiation with self-renewal capabilities, and therapeutic resistance are proposed to contribute to the onset of CRPC. In this review, we discuss the role of CSC in CRPC with the evidence of CSC phenotypes and the possible underlying mechanisms.

CD133 suppression increases the sensitivity of prostate cancer cells to paclitaxel

One of the major barriers in cancer therapy is the resistance to conventional therapies and cancer stem cells (CSCs) are among the main causes of this problem. CD133 as a CSC marker displays stem cell-like properties, tumorigenic capacity, and drug resistance in various cancers. However, the molecular mechanism behind CD133 function in prostate cancer (PC) still remains unclear. This research aimed to illustrate the probabilistic mechanism of CD133-siRNA and paclitaxel in the reduction of chemoresistance in PC cells. To measure the cell viability, migratory capacity, CSCs properties, invasive potential, apoptosis and cell cycle progression of the cells, the MTT, wound healing, spheroid assay, colony formation assay, DAPI staining and flow cytometry assays were applied in the LNCaP cell line, respectively. Also, quantitative real-time PCR (qRT-PCR) and western blot method were used for measuring the expression of CD133 and the effects of CD133 silencing on the AKT/mTOR/c-myc axis and pro-metastatic genes expression. We showed that the CD133-siRNA considerably decreased the CD133 expression. Moreover, CD133-siRNA and paclitaxel treatment significantly decreased cell proliferation and also inhibited the ability of cell migration and invasion and reduced pro-metastatic genes expression. Additionally, we found that the simultaneous use of CD133-siRNA and paclitaxel increased the paclitaxel-induced apoptosis. Our results confirmed that CD133 silencing combined with paclitaxel synergistically could suppress cell migration, invasion, and proliferation and enhance the chemosensitivity compared with mono treatment. Therefore, CD133 silencing therapy could be viewed as a promising and efficient strategy in PC targeted therapies.

Silencing of brain-expressed X-linked 2 (BEX2) promotes colorectal cancer metastasis through the Hedgehog signaling pathway

The incidence of colorectal cancer is increasing, and cancer metastasis is one of the major causes of poor outcomes. BEX2 has been reported to be involved in tumor development in several types of cancer, but its role in metastatic colorectal cancer remains largely undefined. Herein, we demonstrated that BEX2 knockout resulted in enhanced migratory and metastatic potential in colorectal cancer cells both in vitro and in vivo, and re-expression of BEX2 in knockout cells could reverse the enhanced migratory capacity. RNA-Seq results indicated that the hedgehog signaling pathway was activated after BEX2 knockout; moreover, the hedgehog signaling inhibitors, GANT61 and GDC-0449 could reverse the migratory enhancement of BEX2-/- colorectal cancer cells. We also demonstrated that the nuclear translocation of Zic2 after BEX2 silencing could activate the hedgehog signaling pathway, while Zic2 knockdown abrogated the migratory enhancement of BEX2-/- cells and inhibited the hedgehog signaling pathway. In summary, our findings suggest that BEX2 negatively modulates the hedgehog signaling pathway by retaining Zic2 in the cytoplasm in colorectal cancer cells, thereby inhibiting migration and metastasis of colorectal cancer cells.

Hedgehog Signaling for Urogenital Organogenesis and Prostate Cancer: An Implication for the Epithelial-Mesenchyme Interaction (EMI)

Hedgehog (Hh) signaling is an essential growth factor signaling pathway especially in the regulation of epithelial-mesenchymal interactions (EMI) during the development of the urogenital organs such as the bladder and the external genitalia (EXG). The Hh ligands are often expressed in the epithelia, affecting the surrounding mesenchyme, and thus constituting a form of paracrine signaling. The development of the urogenital organ, therefore, provides an intriguing opportunity to study EMI and its relationship with other pathways, such as hormonal signaling. Cellular interactions of prostate cancer (PCa) with its neighboring tissue is also noteworthy. The local microenvironment, including the bone metastatic site, can release cellular signals which can affect the malignant tumors, and vice versa. Thus, it is necessary to compare possible similarities and divergences in Hh signaling functions and its interaction with other local growth factors, such as BMP (bone morphogenetic protein) between organogenesis and tumorigenesis. Additionally, this review will discuss two pertinent research aspects of Hh signaling: (1) the potential signaling crosstalk between Hh and androgen signaling; and (2) the effect of signaling between the epithelia and the mesenchyme on the status of the basement membrane with extracellular matrix structures located on the epithelial-mesenchymal interface.

Short-term aromatase inhibition induces prostatic alterations in adult wistar rat: A biochemical, histopathological and immunohistochemical study

PURPOSE

This study aimed to evaluate the effects of estrogen reduction on amyloid deposition, some lipid metabolism and oxidative stress markers, PSA-like production and p63 expression in the prostate of the adult rat.

METHODS

Aromatase inhibitor: Formestane (4-OHA), was administrated to male rats, at a dose of 0.1 mg/kg b.w./day, for 10 days. The control group (CONT) received the same volume of placebo injection (NaCl 0.9%).

RESULTS

4-OHA treatment induced a significant accumulation of intraprostatic cholesterol (138.90 ± 17.64 vs 85.12 ± 2.87, p = 0.01); against an insignificant diminution of malondialdehyde (412.6 ± 54.35 vs 842.70 ± 336.50, p > 0.05) and glutathione (2.40 ± 0.23 vs 3.65 ± 0.88, p > 0.05). This was associated with a significant decrease of nitric oxide (31.76 ± 7.07 vs 179.40 ± 58.35, p = 0.024). Additionally, 4-OHA significantly increased the intraprostatic production of PSA-like (11.12 ± 2.78 vs 3.91 ± 0.43, p = 0.043). The prostatic histology revealed an amyloid deposition, in all prostatic lobes and a smooth muscle layer growth (p < 0.05); especially significant in the dorsal and lateral lobes. Theses lobes manifested a basal cells proliferation, with a 3-fold increase of p63 expression (p < 0.001). The ventral lobe presented epithelial atrophy (37.80 ± 16.20 vs 167.60 ± 5.16, p < 0.05); with occasional and significant proliferative foci (247.00 ± 9.573 vs 167.60 ± 5.16 p < 0.05).

DISCUSSION AND CONCLUSION

Aromatase inhibition, in the adult male rat, alters the prostatic function by reducing nitric oxide availability and inducing amyloid deposition along with limiting the differentiation of basal cells, through a lobe-specific p63-overexpression.

Bone microenvironment signaling of cancer stem cells as a therapeutic target in metastatic prostate cancer

Prostate cancer (PCa) is one of the most prevalent cancers and the second leading cause of cancer death among US males. When diagnosed in an early disease stage, primary tumors of PCa may be treated with surgical resection or radiation, sometimes combined with androgen deprivation therapy, with favorable outcomes. Unfortunately, the treatment efficacy of each approach decreases significantly in later stages of PCa that involve metastasis to soft tissues and bone. Metastatic PCa is a heterogeneous disease containing host cells, mature cancer cells, and subpopulation of cancer stem cells (CSC). CSCs are highly tumorigenic due to their self-renewing and differentiating potential, clinically resulting in recurrence and resistance to standard therapies. Therefore, there is a large unmet clinical need to develop therapies, which target CSC activity. In this review, we summarize the main signaling pathways that are implicated in the current pre-clinical and clinical studies of recurrent metastatic PCa within the bone microenvironment targeting CSCs and discuss the trajectory of therapeutics moving forward.

Transcriptional Reprogramming and Novel Therapeutic Approaches for Targeting Prostate Cancer Stem Cells

Prostate cancer is the most common malignancy in men and the second cause of cancer-related deaths in western countries. Despite the progress in the treatment of localized prostate cancer, there is still lack of effective therapies for the advanced forms of the disease. Most patients with advanced prostate cancer become resistant to androgen deprivation therapy (ADT), which remains the main therapeutic option in this setting, and progress to lethal metastatic castration-resistant prostate cancer (mCRPC). Current therapies for prostate cancer preferentially target proliferating, partially differentiated, and AR-dependent cancer cells that constitute the bulk of the tumor mass. However, the subpopulation of tumor-initiating or tumor-propagating stem-like cancer cells is virtually resistant to the standard treatments causing tumor relapse at the primary or metastatic sites. Understanding the pathways controlling the establishment, expansion and maintenance of the cancer stem cell (CSC) subpopulation is an important step toward the development of more effective treatment for prostate cancer, which might enable ablation or exhaustion of CSCs and prevent treatment resistance and disease recurrence. In this review, we focus on the impact of transcriptional regulators on phenotypic reprogramming of prostate CSCs and provide examples supporting the possibility of inhibiting maintenance and expansion of the CSC pool in human prostate cancer along with the currently available methodological approaches. Transcription factors are key elements for instructing specific transcriptional programs and inducing CSC-associated phenotypic changes implicated in disease progression and treatment resistance. Recent studies have shown that interfering with these processes causes exhaustion of CSCs with loss of self-renewal and tumorigenic capability in prostate cancer models. Targeting key transcriptional regulators in prostate CSCs is a valid therapeutic strategy waiting to be tested in clinical trials.

Dysregulated gene expression predicts tumor aggressiveness in African-American prostate cancer patients

Molecular mechanisms underlying the health disparity of prostate cancer (PCa) have not been fully determined. In this study, we applied bioinformatic approach to identify and validate dysregulated genes associated with tumor aggressiveness in African American (AA) compared to Caucasian American (CA) men with PCa. We retrieved and analyzed microarray data from 619 PCa patients, 412 AA and 207 CA, and we validated these genes in tumor tissues and cell lines by Real-Time PCR, Western blot, immunocytochemistry (ICC) and immunohistochemistry (IHC) analyses. We identified 362 differentially expressed genes in AA men and involved in regulating signaling pathways associated with tumor aggressiveness. In PCa tissues and cells, NKX3.1, APPL2, TPD52, LTC4S, ALDH1A3 and AMD1 transcripts were significantly upregulated (p < 0.05) compared to normal cells. IHC confirmed the overexpression of TPD52 (p = 0.0098) and LTC4S (p < 0.0005) in AA compared to CA men. ICC and Western blot analyses additionally corroborated this observation in PCa cells. These findings suggest that dysregulation of transcripts in PCa may drive the disparity of PCa outcomes and provide new insights into development of new therapeutic agents against aggressive tumors. More studies are warranted to investigate the clinical significance of these dysregulated genes in promoting the oncogenic pathways in AA men.

Targeting GLI Transcription Factors in Cancer

Aberrant activation of hedgehog (Hh) signaling has been observed in a wide variety of tumors and accounts for more than 25% of human cancer deaths. Inhibitors targeting the Hh signal transducer Smoothened (SMO) are widely used and display a good initial efficacy in patients suffering from basal cell carcinoma (BCC); however, a large number of patients relapse. Though SMO mutations may explain acquired therapy resistance, a growing body of evidence suggests that the non-canonical, SMO-independent activation of the Hh pathway in BCC patients can also account for this adverse effect. In this review, we highlight the importance of glioma-associated oncogene (GLI) transcription factors (the main downstream effectors of the canonical and the non-canonical Hh cascade) and their putative role in the regulation of multiple oncogenic signaling pathways. Moreover, we discuss the contribution of the Hh signaling to malignant transformation and propose GLIs as central hubs in tumor signaling networks and thus attractive molecular targets in anti-cancer therapies.

Gli-1/PI3K/AKT/NF-kB pathway mediates resistance to radiation and is a target for reversion of responses in refractory acute myeloid leukemia cells

Total body irradiation combined with chemotherapy is currently the most effective procedure as a preparative myeloablative regimen. However, resistance to radiotherapy and chemotherapy in refractory acute myeloid leukemia is associated with short-time recurrence after allogeneic hematopoietic stem cell transplantation. To address this issue, we used three cell lines, HL60, HL60/ADR (adriamycin-resistant cells), and HL60/RX (a radiation-resistant cell line established from HL60 cells), as cellular models to investigate the mechanism of the Hedgehog (Hh) signaling pathway resulting in radioresistance, and the efficacy of LDE225 (an inhibitor of the Hh pathway) to enhance radiation sensitivity. Our results indicated that HL60/RX and HL60/ADR cells showed an increased in radioresistance and elevated activity of Hh pathway proteins compared with HL60 cells (P<0.001). In addition, LDE225 significantly reduced clonogenic survival with a sensitivity enhancement ratio (SER) of 1.283 for HL60/ADR and 1.245 for HL60/RX cells. The combination of LDE225 with irradiation significantly increased radiation-induced apoptosis and expression of γ-H2AX and BAK compared with single-treatment groups in both HL60/RX and HL60/ADR cells (P<0.001). In vivo, the combination of LDE225 with irradiation exerted a significant antitumor effect compared with the control and single agents in HL60/RX- and HL60/ADR-xenografted mouse models (P<0.001). Furthermore, our data obtained from western blot and IHC analyses showed that the activation of pAKT and NF-kB was reduced by LDE225 treatment in both HL60/ADR and HL60/RX cells. This demonstrates that the Gli-1/PI3K/AKT/NF-kB pathway plays a key role in resistance to radiation, and that inhibition of the Hh pathway sensitizes cells to radiation by overcoming radioresistance.

Prostate Cancer Stem Cells and Nanotechnology: A Focus on Wnt Signaling

Prostate cancer is the most common cancer among men worldwide. However, current treatments for prostate cancer patients in advanced stage often fail because of relapse. Prostate cancer stem cells (PCSCs) are resistant to most standard therapies, and are considered to be a major mechanism of cancer metastasis and recurrence. In this review, we summarized current understanding of PCSCs and their self-renewal signaling pathways with a specific focus on Wnt signaling. Although multiple Wnt inhibitors have been developed to target PCSCs, their application is still limited by inefficient delivery and toxicity in vivo. Recently, nanotechnology has opened a new avenue for cancer drug delivery, which significantly increases specificity and reduces toxicity. These nanotechnology-based drug delivery methods showed great potential in targeting PCSCs. Here, we summarized current advancement of nanotechnology-based therapeutic strategies for targeting PCSCs and highlighted the challenges and perspectives in designing future therapies to eliminate PCSCs.

Adiponectin deficiency contributes to the development and progression of benign prostatic hyperplasia in obesity

The incidence of benign prostatic hyperplasia (BPH) is increasing among obese individuals, but few studies have fully explained the underlying mechanisms. We aimed to elucidate the relationship between obesity and BPH. Herein, we show that in prostatic epithelial and stromal cells, adiponectin exerts multifunctional effects including anti-proliferation, blocking of G1/S-phase progression and the promotion of apoptosis via inhibiting the MEK-ERK-p90RSK axis. Furthermore, we found that a high-fat diet (HFD) led to adiponectin deficiency and microscopic BPH in a mouse model of obesity. And an adiponectin supplement protected the obese mice from microscopic BPH. The present study provides evidence that adiponectin is a protective regulator in the development and progression of BPH and that adiponectin deficiency causally links BPH with obesity.

Immunohistochemical expression of stem cell markers CD44 and nestin in glioblastomas: Evaluation of their prognostic significance

Glioblastoma (GB) is a highly aggressive brain tumor with dismal prognosis and its standard of care consists of surgery followed by radiotherapy plus adjuvant chemotherapy with temozolomide (Stupp protocol). The response to therapy is variable and may be affected by the presence, within the tumor, of a proportion of cancer stem cells, implicated in chemo- and radioresistance. The expression of the stem cell markers nestin and CD44 in GBs has been extensively investigated. The aim of our study was to compare the immunohistochemical expression of nestin and CD44 in 25 cases of GBs and evaluate their possible prognostic value in relation to overall survival time. We found that their expression was strongly correlated (p=0.0090e r=0.5320) and this finding was confirmed by observation with double staining techniques. For the first time, we made a separate immunohistochemical examination of membrane and cytoplasmic nestin staining, finding that although the two signals correlated (p=0.0184, r=0.4678), they had different impact on survival (respectively p=0.0255 and p=0.6376). Enhanced CD44 expression was associated with poor survival rates even if this finding was not statistically significant (p=0.4481, ĸ(2)=0.5755). Overall, membrane nestin signal was found to be a valid prognostic factor. Furthermore, the detection of CD44 in GBs could be of value also as predictive marker; hyaluronan-based nanoparticles have already shown an active targeting of this antigen in other tumors.

Flaxseed reduces epithelial proliferation but does not affect basal cells in induced benign prostatic hyperplasia in rats

PURPOSE

This study aimed to quantitatively and qualitatively evaluate the effects of a flaxseed-based diet on the histoarchitecture of the prostate of normal Wistar rats and of rats with induced BPH.

METHODS

The study included four experimental groups of ten animals each: casein control group (CCG), who were fed a casein-based diet; flaxseed control group (FCG), who were fed a flaxseed-based diet; hyperplasia-induced casein group (HICG), who were fed a casein-based diet; and hyperplasia-induced flaxseed group (HIFG), who were fed a flaxseed-based diet. Hyperplasia was induced by the subcutaneous implantation of silicone pellets containing testosterone propionate. After 20 weeks, the rats were euthanized and their prostate fixed in buffered formalin. Tissue sections were stained with HE, picrosirius red and immunostained for nuclear antigen p63. Histomorphometric analysis evaluated the epithelial thickness, epithelial area, individual luminal area, and total area of prostatic alveoli.

RESULTS

The mean epithelial thickness obtained for HIFG and HICG was 16.52 ± 1.65 and 20.58 ± 2.86 µm, respectively. The mean epithelial thickness in HICG was greater than that in the other groups tested. HIFG had a smaller epithelial thickness and lower percentage of papillary projections in the prostatic alveoli. No significant difference was observed between CCG and FCG. The total area and mean alveolar area showed no significant differences between the groups. The number of cells immunostained for p63 was not significantly different between the groups evaluated.

CONCLUSION

These results suggest that flaxseed has a protective effect on the prostate epithelium in BPH-induced animals.

CD44, Sonic Hedgehog, and Gli1 Expression Are Prognostic Biomarkers in Gastric Cancer Patients after Radical Resection

Aim. CD44 and Sonic Hedgehog (Shh) signaling are important for gastric cancer (GC). However, the clinical impact, survival, and recurrence outcome of CD44, Shh, and Gli1 expressions in GC patients following radical resection have not been elucidated. Patients and Methods. CD44, Shh, and Gli1 protein levels were quantified by immunohistochemistry (IHC). The association between CD44, Shh, and Gli1 expression and clinicopathological features or prognosis of GC patients was determined. The biomarker risk score was calculated by the IHC staining score of CD44, Shh, and Gli1 protein. Results. The IHC positive staining of CD44, Shh, and Gli1 proteins was correlated with larger tumour size, worse gross type and histological type, and advanced TNM stage, which also predicted shorter overall survival (OS) and disease-free survival (DFS) after radical resection. Multivariate analysis indicated the Gli1 protein and Gli1, CD44 proteins were predictive biomarkers for OS and DFS, respectively. If biomarker risk score was taken into analysis, it was the independent prognostic factor for OS and DFS. Conclusions. CD44 and Shh signaling are important biomarkers for tumour aggressiveness, survival, and recurrence in GC.

Hedgehog Signaling in the Maintenance of Cancer Stem Cells

Cancer stem cells (CSCs) represent a rare population of cells with the capacity to self-renew and give rise to heterogeneous cell lineages within a tumour. Whilst the mechanisms underlying the regulation of CSCs are poorly defined, key developmental signaling pathways required for normal stem and progenitor functions have been strongly implicated. Hedgehog (Hh) signaling is an evolutionarily-conserved pathway essential for self-renewal and cell fate determination. Aberrant Hh signaling is associated with the development and progression of various types of cancer and is implicated in multiple aspects of tumourigenesis, including the maintenance of CSCs. Here, we discuss the mounting evidence suggestive of Hh-driven CSCs in the context of haematological malignancies and solid tumours and the novel strategies that hold the potential to block many aspects of the transformation attributed to the CSC phenotype, including chemotherapeutic resistance, relapse and metastasis.

Hedgehog signaling in prostate epithelial-mesenchymal growth regulation

The prostate gland plays an important role in male reproduction, and is also an organ prone to diseases such as benign prostatic hyperplasia (BPH) and prostate cancer. The prostate consists of ducts with an inner layer of epithelium surrounded by stroma. Reciprocal signaling between these two cell compartments is instrumental to normal prostatic development, homeostasis, regeneration, as well as tumor formation. Hedgehog (HH) signaling is a master regulator in numerous developmental processes. In many organs, HH plays a key role in epithelial-mesenchymal signaling that regulates organ growth and tissue differentiation, and abnormal HH signaling has been implicated in the progression of various epithelial carcinomas. In this review, we focus on recent studies exploring the multipotency of endogenous postnatal and adult epithelial and stromal stem cells and studies addressing the role of HH in prostate development and cancer. We discuss the implications of the results for a new understanding of prostate development and disease. Insight into the cellular and molecular mechanisms underlying epithelial-mesenchymal growth regulation should provide a basis for devising innovative therapies to combat diseases of the prostate.

Roles for Hedgehog signaling in adult organ homeostasis and repair

The hedgehog (HH) pathway is well known for its mitogenic and morphogenic functions during development, and HH signaling continues in discrete populations of cells within many adult mammalian tissues. Growing evidence indicates that HH regulates diverse quiescent stem cell populations, but the exact roles that HH signaling plays in adult organ homeostasis and regeneration remain poorly understood. Here, we review recently identified functions of HH in modulating the behavior of tissue-specific adult stem and progenitor cells during homeostasis, regeneration and disease. We conclude that HH signaling is a key factor in the regulation of adult tissue homeostasis and repair, acting via multiple different routes to regulate distinct cellular outcomes, including maintenance of plasticity, in a context-dependent manner.

Molecular pathways and targets in prostate cancer

Prostate cancer co-opts a unique set of cellular pathways in its initiation and progression. The heterogeneity of prostate cancers is evident at earlier stages, and has led to rigorous efforts to stratify the localized prostate cancers, so that progression to advanced stages could be predicted based upon salient features of the early disease. The deregulated androgen receptor signaling is undeniably most important in the progression of the majority of prostate tumors. It is perhaps because of the primacy of the androgen receptor governed transcriptional program in prostate epithelium cells that once this program is corrupted, the consequences of the ensuing changes in activity are pleotropic and could contribute to malignancy in multiple ways. Following localized surgical and radiation therapies, 20-40% of patients will relapse and progress, and will be treated with androgen deprivation therapies. The successful development of the new agents that inhibit androgen signaling has changed the progression free survival in hormone resistant disease, but this has not changed the almost ubiquitous development of truly resistant phenotypes in advanced prostate cancer. This review summarizes the current understanding of the molecular pathways involved in localized and metastatic prostate cancer, with an emphasis on the clinical implications of the new knowledge.

Phosphodiesterase 4D inhibitors limit prostate cancer growth potential

Phosphodiesterase 4D (PDE4D) has recently been implicated as a proliferation-promoting factor in prostate cancer and is overexpressed in human prostate carcinoma. However, the effects of PDE4D inhibition using pharmacologic inhibitors have not been examined in prostate cancer. These studies examined the effects of selective PDE4D inhibitors, NVP-ABE171 and cilomilast, as anti-prostate cancer therapies in both in vitro and in vivo models. The effects of PDE4D inhibitors on pathways that are critical in prostate cancer and/or downstream of cyclic AMP (cAMP) were examined. Both NVP-ABE171 and cilomilast decreased cell growth. In vitro, PDE4D inhibitors lead to decreased signaling of the sonic hedgehog (SHH), androgen receptor (AR), and MAPK pathways, but growth inhibition was best correlated to the SHH pathway. PDE4D inhibition also reduced proliferation of epithelial cells induced by paracrine signaling from cocultured stromal cells that had activated hedgehog signaling. In addition, PDE4D inhibitors decreased the weight of the prostate in wild-type mice. Prostate cancer xenografts grown in nude mice that were treated with cilomilast or NVP-ABE171 had decreased wet weight and increased apoptosis compared with vehicle-treated controls. These studies suggest the pharmacologic inhibition of PDE4D using small-molecule inhibitors is an effective option for prostate cancer therapy.

IMPLICATIONS

PDE4D inhibitors decrease the growth of prostate cancer cells in vivo and in vitro, and PDE4D inhibition has therapeutic potential in prostate cancer.

KCTD11 tumor suppressor gene expression is reduced in prostate adenocarcinoma

Prostate cancer is the most common noncutaneous cancer among men in the United States. A genetic contribution to prostate cancer risk has been documented, but knowledge of the molecular mechanisms involved in prostate cancer initiation is still not well understood. Loss of heterozygosity (LOH) of chromosomal regions is crucial in tumor progression. In human prostate cancer, several chromosomal regions demonstrating a high frequency of LOH have been previously identified. KCTD11 (REN) is a tumor suppressor gene mapping on human chromosome 17p13.2, whose expression is frequently lost in human medulloblastoma and in several other cancer types. KCTD11 acts as a negative regulator of the Hedgehog (Hh) signaling. Here, we demonstrated that KCTD11 LOH is a common genetic lesion in human prostate adenocarcinoma. Indeed, nuclear KCTD11 protein expression is strongly reduced in primary prostate cancer, and this event correlated with overexpression of proteins acting into the Hedgehog pathway. Low levels of KCTD11 mRNA have been also observed in prostatic cancer cells, and ectopic overexpression of KCTD11 led to growth arrest. Our study demonstrates and supports that KCTD11, as well as negatively regulated downstream effectors belonging to Hh signaling, plays a role in prostate cancer pathogenesis. This could be suitable to characterize new diagnostic and therapeutic markers.

Contributions of epithelial-mesenchymal transition and cancer stem cells to the development of castration resistance of prostate cancer

An important clinical challenge in prostate cancer therapy is the inevitable transition from androgen-sensitive to castration-resistant and metastatic prostate cancer. Albeit the androgen receptor (AR) signaling axis has been targeted, the biological mechanism underlying the lethal event of androgen independence remains unclear. New emerging evidences indicate that epithelial-to-mesenchymal transition (EMT) and cancer stem cells (CSCs) play crucial roles during the development of castration-resistance and metastasis of prostate cancer. Notably, EMT may be a dynamic process. Castration can induce EMT that may enhance the stemness of CSCs, which in turn results in castration-resistance and metastasis. Reverse of EMT may attenuate the stemness of CSCs and inhibit castration-resistance and metastasis. These prospective approaches suggest that therapies target EMT and CSCs may cast a new light on the treatment of castration-resistant prostate cancer (CRPC) in the future. Here we review recent progress of EMT and CSCs in CRPC.

Sonic hedgehog signals to multiple prostate stromal stem cells that replenish distinct stromal subtypes during regeneration

The adult mouse prostate has a seemingly endless capacity for regeneration, and sonic hedgehog (SHH) signaling has been implicated in this stem cell-driven process. However, it is not clear whether SHH acts on the epithelium or stromal cells that secrete factors required for epithelial expansion. Because little is known about stromal stem cells compared with their epithelial counterparts, we used in vivo mouse genetics tools to characterize four prostate stromal subtypes and their stem cells. Using knockin reporter alleles, we uncovered that SHH signals from prostate basal epithelial cells to adjacent stromal cells. Furthermore, the SHH target gene Gli1 is preferentially expressed in subepithelial fibroblast-like cells, one of four prostate stromal subtypes and the subtype closest to the epithelial source of SHH. Using Genetic Inducible Fate Mapping to mark adult Gli1- or Smooth muscle actin-expressing cells and follow their fate during regeneration, we uncovered that Gli1-expressing cells exhibit long-term self-renewal capacity during multiple rounds of androgen-mediated regeneration after castration-induced involution, and depleted smooth muscle cells are mainly replenished by preexisting smooth muscle cells. Based on our Genetic Inducible Fate Mapping studies, we propose a model where SHH signals to multiple stromal stem cells, which are largely unipotent in vivo.

The GLI1 splice variant TGLI1 promotes glioblastoma angiogenesis and growth

We investigated truncated glioma-associated oncogene homolog 1 (TGLI1) that behaves as gain-of-function GLI1 and promotes tumor cell migration and invasion. Herein, we report that TGLI1 had a higher propensity than GLI1 to enhance glioblastoma angiogenesis and growth, both in vivo and in vitro. TGLI1 has gained the ability to enhance expression of pro-angiogenic heparanase. In patient glioblastomas, TGLI1 levels are correlated with heparanase expression. Together, we report that TGLI1 is a novel mediator of glioblastoma angiogenesis and that heparanase is a novel transcriptional target of TGLI1, shedding new light on the molecular pathways that support tumor angiogenesis and aggressive growth.

Hedgehog signaling pathway and ovarian cancer

Epithelial ovarian carcinoma (EOC) is the most common form of ovarian malignancies and the most lethal gynecologic malignancy in the United States. To date, in spite of treatment to it with the extensive surgical debulking and chemotherapy, the prognosis of EOC remains dismal. Recently, it has become increasingly clear that in many instances, the signaling and molecular players that control development are the same, and when inappropriately regulated, drive tumorigenesis and cancer development. Here, we discuss the possible involvement of Hedgehog (Hh) pathway in the cellular regulation and development of cancer in the ovaries. Using the in vitro and in vivo assays developed has facilitated the dissection of the mechanisms behind Hh-driven ovarian cancers formation and growth. Based on recent studies, we propose that the inhibition of Hh signaling may interfere with spheroid-like structures in ovarian cancers. The components of the Hh signaling may provide novel drug targets, which could be explored as crucial combinatorial strategies for the treatment of ovarian cancers.

Effect of sarcosine on antioxidant parameters and metallothionein content in the PC-3 prostate cancer cell line

Sarcosine is currently one of the most discussed markers of prostate cancer. It is involved in amino acid metabolism and methylation processes that occur during the progression of prostate cancer. In this study, we monitored the effect of the addition of sarcosine (0; 10; 250; 500; 1,000 and 1,500 µM) in a time-dependent manner (0-72 h) on the PC-3 prostate cancer cell line. For the assessment of cell viability, the commonly used MTT test was employed. Furthermore, ion-exchange liquid chromatography was used for the determination of sarcosine content in the PC-3 cells. We also determined metallothionein (MT) levels by chip capillary electrophoresis and Brdicka reaction in the cells treated with sarcosine. Sarcosine levels in the cells increased in a concentration-dependent manner levels increased from only 270 nM with the lowest applied concentration of sarcosine (10 µM) to 106 µM with the highest applied concentration of sarcosine (1,500 µM). There was a marginal change observed in the MT concentration. Finally, the antioxidant activity of the PC-3 cells was determined using five different spectrophotometric methods [2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing ability of plasma (FRAP), free radicals, N,N-dimethyl-p-phenylenediamine (DMPD) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS)]. A significant negative correlation was observed between DPPH and FRAP (r=-0.68 at p<0.001) and between DMPD and ABST (r=-0.64 at p<0.001). Additionally, as regards the correlation between MT and DPPH, a significant positive trend (r=0.62 at p<0.001) was observed.

Recent advances in prostate development and links to prostatic diseases

The prostate is a branched ductal-acinar gland that is part of the male reproductive tract. Prostate development depends upon the integration of steroid hormone signals, paracrine interactions between the stromal and epithelial tissue layers, and the actions of cell autonomous factors. Several genes and signaling pathways are known to be required for one or more steps of prostate development including epithelial budding, duct elongation, branching morphogenesis, and/or cellular differentiation. Recent progress in the field of prostate development has included the application of genome-wide technologies including serial analysis of gene expression, expression profiling microarrays, and other large-scale approaches to identify new genes and pathways that are essential for prostate development. The aggregation of experimental results into online databases by organized multilab projects including the Genitourinary Developmental Molecular Atlas Project has also accelerated the understanding of molecular pathways that function during prostate development and identified links between prostate anatomy and molecular signaling. Rapid progress has also recently been made in understanding the nature and role of candidate stem cells in the developing and adult prostate. This has included the identification of putative prostate stem cell markers, lineage tracing, and organ reconstitution studies. However, several issues regarding their origin, precise nature, and possible role(s) in disease remain unresolved. Nevertheless, several links between prostatic developmental mechanisms and the pathogenesis of prostatic diseases including benign prostatic hyperplasia and prostate cancer have led to recent progress on targeting developmental pathways as therapeutic strategies for these diseases.

Hedgehog signalling pathway: carcinogenesis and targeted therapy

Hedgehog signalling pathway has not only a critical role in cell proliferation,differentiation and tissue polarity at embryonic period but also has a vital role in stem cell proliferation, tissue healing and carcinogenesis. Recent research has increased our understanding of this pathway and its relation to other signalling pathways. In addition, a large number of studies confirmed the alteration of Hh signalling pathway in various types of human malignancies including basal cell carcinomas, medulloblastomas, lung, gastrointestinal, ovarian, breast, prostate cancers and leukemia. More than 50 small biomolecules have been introduced which have inhibitory effects on Hh signalling pathway. Although, in many tumors some acceptable results have been showed in phase I clinical trial, closer studies are required to improve drug bioavailability, to decrease the side effects and to find the right small molecules for specific types of cancers, considering patients overall benefits as well.

Dynamic regulation of cancer stem cells and clinical challenges

A small population of cancer cells referred to as cancer stem cells (CSCs) have received particular attention, as they have been revealed to acquire stem cell-like properties and become the main cause of tumor propagation, metastasis and drug resistance. The CSC theory of tumor formation was believed to follow the hierarchical model initially, and therefore many CSC-targeted therapy methods were expected to cure cancer by eradicating CSCs. However, subsequent CSC research has revealed that rather than a distinct entity, the CSC is a dynamic status that can be continually dedifferentiated from progenitor or differentiated cancer cells. Elucidation of this bidirectional transition mechanism would help perfect the CSC theory and be of great value in the development of more effective anti-cancer drugs. Here, we reviewed the mechanisms of reciprocal conversion between non-CSCs and CSCs. Moreover, several approaches of target CSCs and non-CSCs together with unbiased eradication of all cancer cells are also discussed.

Inhibition of hedgehog signaling depresses self-renewal of pancreatic cancer stem cells and reverses chemoresistance

Pancreatic cancer stem cells play a crucial role in tumorigenesis and chemoresistance. The Hedgehog signaling pathway is a key regulator in pancreatic tumorigenesis and drug resistance. To identify pancreatic cancer stem cells, tumorspheres derived from the PANC-1 pancreatic cancer cell line were cultured under a floating-culture system. PANC-1 tumorspheres possessed properties of self-renewal, differentiation, higher tumorigenesis and chemoresistance. It was observed that Hedgehog pathway is active in PANC-1 tumorspheres as shown by expression of hedgehog components Smo, Gil 1 and Gli 2, detected by quantitative RT-PCR and western blotting. After cyclopamine-mediated blockade of hedgehog, a decrease in proliferation of PANC-1 tumorspheres and G0/G1 transition were observed, as well as a decreased expression of Bmi-1 in PANC-1 tumorspheres. Cyclopamine reversed chemoresistance to gemcitabine, resulting in decreased expression of ABCG2 in PANC-1 tumorspheres. Taken together, our data indicate that PANC-1 tumorspheres have 'stemness' potential, and hedgehog signaling pathway plays an important role in the regulation of self-renewal and reversal of chemoresistance in cancer stem cells in pancreatic adenocarcinoma.

The emerging role of histone lysine demethylases in prostate cancer

Early prostate cancer (PCa) is generally treatable and associated with good prognosis. After a variable time, PCa evolves into a highly metastatic and treatment-refractory disease: castration-resistant PCa (CRPC). Currently, few prognostic factors are available to predict the emergence of CRPC, and no curative option is available. Epigenetic gene regulation has been shown to trigger PCa metastasis and androgen-independence. Most epigenetic studies have focused on DNA and histone methyltransferases. While DNA methylation leads to gene silencing, histone methylation can trigger gene activation or inactivation, depending on the target amino acid residues and the extent of methylation (me1, me2, or me3). Interestingly, some histone modifiers are essential for PCa tumor-initiating cell (TIC) self-renewal. TICs are considered the seeds responsible for metastatic spreading and androgen-independence. Histone Lysine Demethylases (KDMs) are a novel class of epigenetic enzymes which can remove both repressive and activating histone marks. KDMs are currently grouped into 7 major classes, each one targeting a specific methylation site. Since their discovery, KDM expression has been found to be deregulated in several neoplasms. In PCa, KDMs may act as either tumor suppressors or oncogenes, depending on their gene regulatory function. For example, KDM1A and KDM4C are essential for PCa androgen-dependent proliferation, while PHF8 is involved in PCa migration and invasion. Interestingly, the possibility of pharmacologically targeting KDMs has been demonstrated. In the present paper, we summarize the emerging role of KDMs in regulating the metastatic potential and androgen-dependence of PCa. In addition, we speculate on the possible interaction between KDMs and other epigenetic effectors relevant for PCa TICs. Finally, we explore the role of KDMs as novel prognostic factors and therapeutic targets. We believe that studies on histone demethylation may add a novel perspective in our efforts to prevent and cure advanced PCa.

Hedgehog pathway as a drug target: Smoothened inhibitors in development

Emerging laboratory and clinical investigations demonstrate that Hedgehog signaling (Hh) represents a novel therapeutic target in various human cancers. This conserved signaling pathway precisely regulates self-renewal and terminal differentiation in embryonic development, but is typically silenced in adult tissues, with reactivation usually only during tissue repair. Aberrant Hh pathway signaling has been implicated in the pathogenesis, self-renewal, and chemotherapy resistance of a growing number of solid and hematologic malignancies. Major components of the Hh pathway include the Hh ligands (Sonic, Desert, and Indian), the transmembrane receptor Patched, the signal transducer Smoothened (Smo), and transcription factors Gli1–3 which regulate the transcription of Hh target genes. Mutations in Hh pathway genes, increased Hh signaling in tumor stroma, and Hh overexpression in self-renewing cells (cancer stem cells) have been described, and these different modes of Hh signaling have implications for the design of Hh pathway inhibitors and their integration into conventional treatment regimens. Discovery of a naturally-occurring Smo inhibitor, cyclopamine, and the identification of Hh pathway mutations and over expression in cancer cells prompted the development of several cyclopamine derivatives. Encouraging laboratory and in vivo data has resulted in Phase I and II clinical trials of Smo inhibitors. In this review, we will discuss the current understanding of Hh pathway signaling in malignancy and Smo antagonists in development. Recent data with these agents shows that they are well-tolerated and may be effective for subsets of patients. Challenges remain for appropriate patient selection and the optimal combination and sequence of these targeted therapies into current treatment paradigms.

Inhibition of Gli1 results in altered c-Jun activation, inhibition of cisplatin-induced upregulation of ERCC1, XPD and XRCC1, and inhibition of platinum-DNA adduct repair

The transcription of ERCC1 and other nucleotide excision repair (NER) genes is strongly influenced by c-jun. C-jun is transcriptionally regulated by Gli proteins of the Hedgehog pathway. We therefore studied the possible relationships between Gli1, c-jun, and the upregulation of ERCC1, XPD and XRCC1 in cisplatin-resistant human ovarian cancer cells. We studied the paired human ovarian cancer cell lines A2780 and A2780-CP70. We used a shRNA construct that specifically degrades Gli1 message. Genes we assessed for mRNA and/or protein levels included: c-jun, ERCC1, XPD, XRCC1, Gli1, Gli2, SHH, IHH, GAPDH and α-tubulin. Platinum-DNA adduct repair was assessed by atomic absorbance spectrometry with Zeeman background correction. Use of the anti-Gli1 shRNA in cisplatin-resistant cells resulted in a block of the cell's ability to upregulate genes in response to cisplatin treatment, including: c-jun, ERCC1, XPD and XRCC1. This block in upregulation of c-jun was concurrent with a change in the phosphorylation pattern of the c-jun protein, shifting that pattern from a Ser63/73 dominant pattern, to a Thr91/93 dominant pattern. A2780-CP70 cells were treated at their cisplatin IC50, and DNA repair was assessed after pretreatment with anti-Gli1 shRNA or scrambled shRNA control. Control cells repaired 78% of platinum-DNA adducts at 12 h, compared with 33% repair in cells pretreated with anti-Gli1 shRNA resulting in a 2.4-fold difference. Pretreatment of A2780-CP70 cells with anti-Gli1 shRNA resulted in supra-additive cell killing with cisplatin; shifting the cisplatin IC50 (half maximal inhibitory concentration) from 30 μM to 5 μM. Pretreatment of these cells with cyclopamine did not shift the cisplatin IC50. We conclude that the transcriptional protein Gli1 is important in the upregulation of these three DNA repair genes in human ovarian cancer cells, and that Gli1 strongly influences platinum-DNA adduct repair, and cellular sensitivity to cisplatin. This Gli1 role has c-jun as an intermediate in the pathway. In all, inhibition of Gli1 by a specific shRNA inhibits the upregulation of c-jun Ser63/73, and also inhibits the upregulation of three genes essential to NER (ERCC1, XPD) and base excision repair (XRCC1).

Wnt and SHH in prostate cancer: trouble mongers occupy the TRAIL towards apoptosis

Prostate cancer is a serious molecular disorder that arises because of reduction in tumour suppressors and overexpression of oncogenes. The malignant cells survive within the context of a three-dimensional microenvironment in which they are exposed to mechanical and physical cues. These signals are, nonetheless, deregulated through perturbations to mechanotransduction, from the nanoscale level to the tissue level. Increasingly sophisticated interpretations have uncovered significant contributions of signal transduction cascades in governing prostate cancer progression. To dismantle the major determinants that lie beneath disruption of spatiotemporal patterns of activity, crosstalk between various signalling cascades and their opposing and promoting effects on TRAIL-mediated activities cannot be ruled out. It is important to focus on that molecular multiplicity of cancer cells, various phenotypes reflecting expression of a variety of target oncogenes, reversible to irreversible, exclusive, overlapping or linked, coexist and compete with each other. Comprehensive investigations into TRAIL-mediated mitochondrial dynamics will remain a worthwhile area for underlining causes of tumourigenesis and for unravelling interference options.

Intravitreal homocysteine-thiolactone injection leads to the degeneration of multiple retinal cells, including photoreceptors

PURPOSE

Hyperhomocysteinemia is known to cause degeneration of retinal ganglion cells, but its influence on photoreceptors remains largely unknown. In particular, the role of homocysteine-thiolactone (Hcy-T)--the physiologic metabolite of homocysteine that has been proven to be more cytotoxic than homocysteine itself--as a factor that causes retinopathy, has not been defined. This study aimed to investigate the toxic effects of excessive Hcy-T in a mouse model.

METHODS

A total of 60 six-week-old female ICR mice were used in this study. The mice were divided into 3 experimental groups and 2 control groups. The mice in the experimental groups were subjected to intravitreal injections of Hcy-T to reach final estimated intravitreal concentrations at 5, 25, and 200 μM, respectively. Mice without injection (blank) and with 0.9 NaCl injections (sham injection) were used as controls. The mice with 200 μM Hcy-T were sacrificed at days 7, 15, 45, and 90 after injection and the mice with 5 or 25 μM Hcy-T were sacrificed at day 90, with the controls sacrificed at day 15 or 90 for comparison. Semi-quantitative dot-blot analysis was performed for confirmation of retinal homocysteinylation. The mouse retinas were evaluated microscopically, with the thickness of total and specific retinal layers determined. Immunohistochemical analysis was performed and the labeled cells were quantified to determine the effects of excessive Hcy-T on specific retinal cells.

RESULTS

Dose-dependent retinal homocysteinylation after Hcy-T injection was confirmed. The homocysteinylation was localized in the outer and inner segments of photoreceptors and the ganglion cell layer (GCL). Retinal cell degenerations were found in the GCL, inner nuclear layer, and outer nuclear layer at day 90 after 200 µM Hcy-T injection. Significant thickness reduction was found in the total retina, outer nuclear layer, and the outer and inner segment layers. A trend of thickness reduction was also found in the GCL and inner nuclear layer, although this was not statistically significant. The rhodopsin⁺ photoreceptors and the calbindin⁺ horizontal cells were significantly reduced at day 15, and were nearly ablated at day 90 after 200 μM Hcy-T injection (p<0.001 for both day 15 and day 90), which was not seen in the sham injection controls. The Chx-10⁺ or the Islet-1⁺ bipolar cells and the Pax-6⁺ amacrine cells were severely misarranged at day 90, but no significant reduction was found for both cell types. The GFAP⁺ Müller cells were activated at day 15, but were not significantly increased at day 90 after the injection.

CONCLUSIONS

Excessive retinal homocysteinylation by Hcy-T, a condition of hyperhomocysteinemia, could lead to degeneration of photoreceptors, which might lead to retinopathies associated with severe hyperhomocysteinemia or diabetes mellitus.

Frequent gene products and molecular pathways altered in prostate cancer- and metastasis-initiating cells and their progenies and novel promising multitargeted therapies

Recent gene expression profiling analyses and gain- and loss-of-function studies performed with distinct prostate cancer (PC) cell models indicated that the alterations in specific gene products and molecular pathways often occur in PC stem/progenitor cells and their progenies during prostate carcinogenesis and metastases at distant sites, including bones. Particularly, the sustained activation of epidermal growth factor receptor (EGFR), hedgehog, Wnt/β-catenin, Notch, hyaluronan (HA)/CD44 and stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor 4 (CXCR4) during the epithelial-mesenchymal transition (EMT) process may provide critical functions for PC progression to locally invasive, metastatic and androgen-independent disease states and treatment resistance. Moreover, an enhanced glycolytic metabolism in PC stem/progenitor cells and their progenies concomitant with the changes in their local microenvironment, including the induction of tumor hypoxia and release of diverse soluble factors by tumor myofibroblasts, also may promote the tumor growth, angiogenesis and metastases. More particularly, these molecular transforming events may cooperate to upregulate Akt, nuclear factor (NF)-κB, hypoxia-inducible factors (HIFs) and stemness gene products such as Oct3/4, Sox2, Nanog and Bmi-1 in PC cells that contribute to their acquisition of high self-renewal, tumorigenic and invasive capacities and survival advantages during PC progression. Consequently, the molecular targeting of these deregulated gene products in the PC- and metastasis-initiating cells and their progenies represent new promising therapeutic strategies of great clinical interest for eradicating the total PC cell mass and improving current antihormonal treatments and docetaxel-based chemotherapies, thereby preventing disease relapse and the death of PC patients.

Getting personal with prostate cancer: adding new pieces to an incomplete jigsaw puzzle

Prostate cancer is a multifaceted molecular anomaly that is insurmountable to date because of the orchestrated network of negative regulators that drive carcinogenesis. A substantial fraction of information has been added that gives yet an unclear snapshot of therapeutic interventions in prostate cancer. Increasing sophisticated interpretations point towards some important aspects of prostate cancer aggressiveness like microRNAs, prostate cancer stem cells and TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) refractoriness. In this review, we will evaluate the push and pull between oncomirs and tumor suppressors in tipping the scales of cancer. Furthermore, multicomponent rational drug designs with a claim to overcome stumbling blocks will be discussed. Translation of the outcomes achieved in the understanding of carcinogenesis at the patient's bedside is possibly the principal challenge in cancer research.