The retinoblastoma protein regulates hypoxia-inducible genetic programs, tumor cell invasiveness and neuroendocrine differentiation in prostate cancer cells

Drug-resilient Cancer Cell Phenotype Is Acquired via Polyploidization Associated with Early Stress Response Coupled to HIF2α Transcriptional Regulation

Therapeutic resistance and recurrence remain core challenges in cancer therapy. How therapy resistance arises is currently not fully understood with tumors surviving via multiple alternative routes. Here, we demonstrate that a subset of cancer cells survives therapeutic stress by entering a transient state characterized by whole-genome doubling. At the onset of the polyploidization program, we identified an upregulation of key transcriptional regulators, including the early stress-response protein AP-1 and normoxic stabilization of HIF2α. We found altered chromatin accessibility, ablated expression of retinoblastoma protein (RB1), and enrichment of AP-1 motif accessibility. We demonstrate that AP-1 and HIF2α regulate a therapy resilient and survivor phenotype in cancer cells. Consistent with this, genetic or pharmacologic targeting of AP-1 and HIF2α reduced the number of surviving cells following chemotherapy treatment. The role of AP-1 and HIF2α in stress response by polyploidy suggests a novel avenue for tackling chemotherapy-induced resistance in cancer.

SIGNIFICANCE

In response to cisplatin treatment, some surviving cancer cells undergo whole-genome duplications without mitosis, which represents a mechanism of drug resistance. This study presents mechanistic data to implicate AP-1 and HIF2α signaling in the formation of this surviving cell phenotype. The results open a new avenue for targeting drug-resistant cells.

Advancement in precision diagnosis and therapeutic for triple-negative breast cancer: Harnessing diagnostic potential of CRISPR-cas & engineered CAR T-cells mediated therapeutics

Cancer is characterized by uncontrolled cell growth, disrupted regulatory pathways, and the accumulation of genetic mutations. These mutations across different types of cancer lead to disruptions in signaling pathways and alterations in protein expression related to cellular growth and proliferation. This review highlights the AKT signaling cascade and the retinoblastoma protein (pRb) regulating cascade as promising for novel nanotheranostic interventions. Through synergizing state-of-the-art gene editing tools like the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas system with nanomaterials and targeting AKT, there is potential to enhance cancer diagnostics significantly. Furthermore, the integration of modified CAR-T cells into multifunctional nanodelivery systems offers a promising approach for targeted cancer inhibition, including the eradication of cancer stem cells (CSCs). Within the context of highly aggressive and metastatic Triple-negative Breast Cancer (TNBC), this review specifically focuses on devising innovative nanotheranostics. For both pre-clinical and post-clinical TNBC detection, the utilization of the CRISPR-Cas system, guided by RNA (gRNA) and coupled with a fluorescent reporter specifically designed to detect TNBC's mutated sequence, could be promising. Additionally, a cutting-edge approach involving the engineering of TNBC-specific iCAR and syn-Notch CAR T-cells, combined with the co-delivery of a hybrid polymeric nano-liposome encapsulating a conditionally replicative adenoviral vector (CRAdV) against CSCs, could present an intriguing intervention strategy. This review thus paves the way for exciting advancements in the field of nanotheranostics for the treatment of TNBC and beyond.

A novel GRK3-HDAC2 regulatory pathway is a key direct link between neuroendocrine differentiation and angiogenesis in prostate cancer progression

The mechanisms underlying the progression of prostate cancer (PCa) to neuroendocrine prostate cancer (NEPC), an aggressive PCa variant, are largely unclear. Two prominent NEPC phenotypes are elevated NE marker expression and heightened angiogenesis. Identifying the still elusive direct molecular links connecting angiogenesis and neuroendocrine differentiation (NED) is crucial for our understanding and targeting of NEPC. Here we found that histone deacetylase 2 (HDAC2), whose role in NEPC has not been reported, is one of the most upregulated epigenetic regulators in NEPC. HDAC2 promotes both NED and angiogenesis. G protein-coupled receptor kinase 3 (GRK3), also upregulated in NEPC, is a critical promoter for both phenotypes too. Of note, GRK3 phosphorylates HDAC2 at S394, which enhances HDAC2's epigenetic repression of potent anti-angiogenic factor Thrombospondin 1 (TSP1) and master NE-repressor RE1 Silencing Transcription Factor (REST). Intriguingly, REST suppresses angiogenesis while TSP1 suppresses NE marker expression in PCa cells, indicative of their novel functions and their synergy in cross-repressing the two phenotypes. Furthermore, the GRK3-HDAC2 pathway is activated by androgen deprivation therapy and hypoxia, both known to promote NED and angiogenesis in PCa. These results indicate that NED and angiogenesis converge on GRK3-enhanced HDAC2 suppression of REST and TSP1, which constitutes a key missing link between two prominent phenotypes of NEPC.

Identification of novel genes by targeted exome sequencing in Retinoblastoma

BACKGROUND

Retinoblastoma (RB) is initiated by mutation in both alleles of RB1 gene. However, few cases may occur even in the absence of RB1 mutation suggesting the role of genes other than RB1.

METHODOLOGY

The current study was planned to utilize targeted exome sequencing in Indian RB patients affected with unilateral non-familial RB. 75 unilateral RB patients below 5 years of age were enrolled. Genomic DNA was extracted from blood and tumor tissue. From peripheral blood DNA, all coding and exon/intron regions were amplified using PCR and direct sequencing. Cases which did not harbor pathogenic variants in peripheral blood DNA were further screened for mutations in their tumor tissue DNA using targeted exome sequencing. Three pathogenicity prediction tools (Mutation Taster, SIFT, and PolyPhen-2) were used to determine the pathogenicity of non-synonymous variations. An in-house bioinformatics pipeline was devised for the mutation screening by targeted exome sequencing. Protein modeling studies were also done to predict the effect of the mutations on the protein structure and function.

RESULTS

Using the mentioned approach, we found two novel variants (g.69673_69674insT and g.48373314C>A) in RB1 gene in peripheral blood DNA. We also found novel variants in eight genes (RB1, ACAD11, GPR151, KCNA1, OTOR, SOX30, ARL11, and MYCT1) that may be associated with RB pathogenesis.

CONCLUSION

The present study expands our current knowledge regarding the genomic landscape of RB and also highlights the importance of NGS technologies to detect genes and novel variants that may play an important role in cancer initiation, progression, and prognosis.

The impact of genetic aberrations on response to radium-223 treatment for castration-resistant prostate cancer with bone metastases

BACKGROUND

Radium (Ra)-223 is an established treatment option for patients with metastatic castrate-resistant prostate cancer (mCRPC) who have symptomatic bone metastases without soft tissue disease. Studies have indicated genetic aberrations that regulate DNA damage response (DDR) in prostate cancer can increase susceptibility to treatments such as poly ADP-ribose polymerase inhibitors and platinum-based therapies. This study aims to evaluate mCRPC response to Ra-223 stratified by tumor genomics.

METHODS

This is a retrospective study of mCRPC patients who received Ra-223 and genetic testing within the Mayo Clinic database (Arizona, Florida, and Minnesota) and Tulane Cancer Center. Patient demographics, genetic aberrations, treatment responses in terms of alkaline phosphatase (ALP) and prostate-specific antigen (PSA), and survival were assessed. Primary end points were ALP and PSA response. Secondary end points were progression-free survival (PFS) and overall survival (OS) from time of first radium treatment.

RESULTS

One hundred and twenty-seven mCRPC patients treated with Ra-223 had germline and/or somatic genetic sequencing. The median age at time of diagnosis and Ra-223 treatment was 61.0 and 68.6 years, respectively. Seventy-nine (62.2%) had Gleason score ≥ 8 at time of diagnosis. 50.4% received prior docetaxel, and 12.6% received prior cabazitaxel. Notable alterations include TP53 (51.7%), BRCA 1/2 (15.0%), PTEN (13.4%), ATM (11.7%), TMPRSS2-ERG (8.2%), RB deletion (3.4%), and CDK12 (1.9%). There was no significant difference in ALP or PSA response among the different genetic aberrations. Patients with a TMPRSS2-ERG mutation exhibited a trend toward lower OS 15.4 months (95% confidence interval [CI] 10.0-NR) versus 26.8 months (95% CI 20.9-35.1). Patients with an RB deletion had a lower PFS 6.0 months (95% CI 1.28-NR) versus 9.0 months (95% CI 7.3-11.1) and a lower OS 13.9 months (95% CI 5.2-NR) versus 26.5 months (95% CI 19.8-33.8).

CONCLUSIONS

Among mCRPC patients treated with Ra-223 at Mayo Clinic and Tulane Cancer Center, we did not find any clear negative predictors of biochemical response or survival to treatment. TMPRSS2-ERG and RB mutations were associated with a worse OS. Prospective studies and larger sample sizes are needed to determine the impact of genetic aberrations in response to Ra-223.

Multi-Omic Meta-Analysis of Transcriptomes and the Bibliome Uncovers Novel Hypoxia-Inducible Genes

Hypoxia is a condition in which cells, tissues, or organisms are deprived of sufficient oxygen supply. Aerobic organisms have a hypoxic response system, represented by hypoxia-inducible factor 1-α (HIF1A), to adapt to this condition. Due to publication bias, there has been little focus on genes other than well-known signature hypoxia-inducible genes. Therefore, in this study, we performed a meta-analysis to identify novel hypoxia-inducible genes. We searched publicly available transcriptome databases to obtain hypoxia-related experimental data, retrieved the metadata, and manually curated it. We selected the genes that are differentially expressed by hypoxic stimulation, and evaluated their relevance in hypoxia by performing enrichment analyses. Next, we performed a bibliometric analysis using gene2pubmed data to examine genes that have not been well studied in relation to hypoxia. Gene2pubmed data provides information about the relationship between genes and publications. We calculated and evaluated the number of reports and similarity coefficients of each gene to HIF1A, which is a representative gene in hypoxia studies. In this data-driven study, we report that several genes that were not known to be associated with hypoxia, including the G protein-coupled receptor 146 gene, are upregulated by hypoxic stimulation.

Significance of TP53 Mutation in Cellular Process and Disease Progression in Lung Adenocarcinoma

Introduction: TP53 (tumor protein p53) is one of the most commonly mutanted genes in lung adenocarcinoma (LUAD). Materials and Methods: In this study, we used data from The Cancer Genome Atlas (TCGA) to evaluate the importance of TP53 mutations in cellular processes, disease progression, the prognosis in LUAD, and to identify critical hub genes and pathways associated with oncogenesis. Results: Analysis of the TCGA data showed TP53 mutations in 22% of LUAD patients. Clinicopathological analyses demonstrated that TP53 mutation was correlated with the disease progression but not prognosis. We identified 1935 differentially expressed genes (DEGs). Functional enrichment analysis showed that the DEGs were mainly concentrated in metabolism, cell differentiation, and cancer-related pathways. The top hub genes were identified and disease analysis revealed the most critical genes related to disease progression and prognosis. The expression levels of several of these genes were then tested in tumor tissues. Conclusion: Our results showed that TP53 mutation plays a critical role in cellular process and the clinicopathological findings in LUAD. We also identified potential key genes, which could provide novel evidence for individualized treatment.

The i-Motif as a Molecular Target: More Than a Complementary DNA Secondary Structure

Stretches of cytosine-rich DNA are capable of adopting a dynamic secondary structure, the i-motif. When within promoter regions, the i-motif has the potential to act as a molecular switch for controlling gene expression. However, i-motif structures in genomic areas of repetitive nucleotide sequences may play a role in facilitating or hindering expansion of these DNA elements. Despite research on the i-motif trailing behind the complementary G-quadruplex structure, recent discoveries including the identification of a specific i-motif antibody are pushing this field forward. This perspective reviews initial and current work characterizing the i-motif and providing insight into the biological function of this DNA structure, with a focus on how the i-motif can serve as a molecular target for developing new therapeutic approaches to modulate gene expression and extension of repetitive DNA.

Cabozantinib can block growth of neuroendocrine prostate cancer patient-derived xenografts by disrupting tumor vasculature

With the advent of potent second-line anti-androgen therapy, we and others have observed an increased incidence of androgen receptor (AR)-null small cell or neuroendocrine prostate cancer (SCNPC) in metastatic castration-resistant prostate cancer (mCRPC). Our study was designed to determine the effect of cabozantinib, a multi-targeted tyrosine kinase inhibitor that inhibits VEGFR2, MET and RET on SCNPC. Transcriptome analysis of the University of Washington rapid autopsy and SU2C mCRPC datasets revealed upregulated MET and RET expression in SCNPCs relative to adenocarcinomas. Additionally, increased MET expression correlated with attenuated AR expression and activity. In vitro treatment of SCNPC patient-derived xenograft (PDX) cells with the MET inhibitor AMG-337 had no impact on cell viability in LuCaP 93 (MET+/RET+) and LuCaP 173.1 (MET-/RET-), whereas cabozantinib decreased cell viability of LuCaP 93, but not LuCaP 173.1. Notably, MET+/RET+ LuCaP 93 and MET-/RET- LuCaP 173.1 tumor volumes were significantly decreased with cabozantinib treatment in vivo, and this activity was independent of MET or RET expression in LuCaP 173.1. Tissue analysis indicated that cabozantinib did not inhibit tumor cell proliferation (Ki67), but significantly decreased microvessel density (CD31) and increased hypoxic stress and glycolysis (HK2) in LuCaP 93 and LuCaP 173.1 tumors. RNA-Seq and gene set enrichment analysis revealed that hypoxia and glycolysis pathways were increased in cabozantinib-treated tumors relative to control tumors. Our data suggest that the most likely mechanism of cabozantinib-mediated tumor growth suppression in SCNPC PDX models is through disruption of the tumor vasculature. Thus, cabozantinib may represent a potential therapy for patients with metastatic disease in tumor phenotypes that have a significant dependence on the tumor vasculature for survival and proliferation.

Molecular tracing of prostate cancer lethality

Prostate cancer is diagnosed mostly in men over the age of 50 years, and has favorable 5-year survival rates due to early cancer detection and availability of curative surgical management. However, progression to metastasis and emergence of therapeutic resistance are responsible for the majority of prostate cancer mortalities. Recent advancement in sequencing technologies and computational capabilities have improved the ability to organize and analyze large data, thus enabling the identification of novel biomarkers for survival, metastatic progression and patient prognosis. Large-scale sequencing studies have also uncovered genetic and epigenetic signatures associated with prostate cancer molecular subtypes, supporting the development of personalized targeted-therapies. However, the current state of mainstream prostate cancer management does not take full advantage of the personalized diagnostic and treatment modalities available. This review focuses on interrogating biomarkers of prostate cancer progression, including gene signatures that correspond to the acquisition of tumor lethality and those of predictive and prognostic value in progression to advanced disease, and suggest how we can use our knowledge of biomarkers and molecular subtypes to improve patient treatment and survival outcomes.

Antagonists of the serotonin receptor 5A target human breast tumor initiating cells

Background

Breast tumor initiating cells (BTIC) are stem-like cells that initiate and sustain tumor growth, and drive disease recurrence. Identifying therapies targeting BTIC has been hindered due primarily to their scarcity in tumors. We previously reported that BTIC frequency ranges between 15% and 50% in multiple mammary tumors of 3 different transgenic mouse models of breast cancer and that this frequency is maintained in tumor cell populations cultured in serum-free, chemically defined media as non-adherent tumorspheres. The latter enabled high-throughput screening of small molecules for their capacity to affect BTIC survival. Antagonists of several serotonin receptors (5-HTRs) were among the hit compounds. The most potent compound we identified, SB-699551, selectively binds to 5-HT5A, a Gα_i/o protein coupled receptor (GPCR).

Methods

We evaluated the activity of structurally unrelated selective 5-HT5A antagonists using multiple orthogonal assays of BTIC frequency. Thereafter we used a phosphoproteomic approach to uncover the mechanism of action of SB-699551. To validate the molecular target of the antagonists, we used the CRISPR-Cas9 gene editing technology to conditionally knockout HTR5A in a breast tumor cell line.

Results

We found that selective antagonists of 5-HT5A reduced the frequency of tumorsphere initiating cells residing in breast tumor cell lines and those of patient-derived xenografts (PDXs) that we established. The most potent compound among those tested, SB-699551, reduced the frequency of BTIC in ex vivo assays and acted in concert with chemotherapy to shrink human breast tumor xenografts in vivo. Our phosphoproteomic experiments established that exposure of breast tumor cells to SB-699551 elicited signaling changes in the canonical Gα_i/o-coupled pathway and the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) axis. Moreover, conditional mutation of the HTR5A gene resulted in the loss of tumorsphere initiating cells and BTIC thus mimicking the effect of SB-699551.

Conclusions

Our data provide genetic, pharmacological and phosphoproteomic evidence consistent with the on-target activity of SB-699551. The use of such agents in combination with cytotoxic chemotherapy provides a novel therapeutic approach to treat breast cancer.

Dedifferentiation of neuroendocrine carcinoma of the uterine cervix in hypoxia

Neuroendocrine carcinoma of small cell type (SCNEC) is a rare pathological subtype in cervical cancer, which has a worse prognosis than other histological cell types. Due to its low incidence and the lack of experimental platforms, the molecular characteristics of SCNEC in the cervix remain largely unknown. Using the cancer tissue-originated spheroid (CTOS) method-an ex vivo 3D culture system that preserves the differentiation status of the original tumors-we established a panel of CTOS lines of SCNEC. We demonstrated that xenograft tumors and CTOSs, respectively, exhibited substantial intra-tumor and intra-CTOS variation in the expression levels of chromogranin A (CHGA), a neuroendocrine tumor marker. Since hypoxia affects differentiation in various tumors and in stem cells, we also investigated how hypoxia affected neuroendocrine differentiation of SCNEC of the uterine cervix. In the CTOS line cerv21, hypoxia suppressed expression of the neuroendocrine markers CHGA and synaptophysin (SYP). Flow cytometry analysis using CD99 (a membrane protein marker of SCNEC) revealed decreased CD99 expression in a subset of cells under hypoxic conditions. These expression changes were attenuated by HIF-1α knockdown, and by a Notch inhibitor, suggesting that these molecules played a role in the regulation of neuroendocrine differentiation. The examined SCNEC markers were suppressed under hypoxia in multiple CTOS lines. Overall, our present results indicated that neuroendocrine differentiation in SCNEC of the uterus is a variable phenotype, and that hypoxia may be one of the factors regulating the differentiation status.

Molecular Links Between Angiogenesis and Neuroendocrine Phenotypes in Prostate Cancer Progression

As a common therapy for prostate cancer, androgen deprivation therapy (ADT) is effective for the majority of patients. However, prolonged ADT promotes drug resistance and progression to an aggressive variant with reduced androgen receptor signaling, so called neuroendocrine prostate cancer (NEPC). Until present, NEPC is still poorly understood, and lethal with no effective treatments. Elevated expression of neuroendocrine related markers and increased angiogenesis are two prominent phenotypes of NEPC, and both of them are positively associated with cancers progression. However, direct molecular links between the two phenotypes in NEPC and their mechanisms remain largely unclear. Their elucidation should substantially expand our knowledge in NEPC. This knowledge, in turn, would facilitate the development of effective NEPC treatments. We recently showed that a single critical pathway regulates both ADT-enhanced angiogenesis and elevated expression of neuroendocrine markers. This pathway consists of CREB1, EZH2, and TSP1. Here, we seek new insights to identify molecules common to pathways promoting angiogenesis and neuroendocrine phenotypes in prostate cancer. To this end, our focus is to summarize the literature on proteins reported to regulate both neuroendocrine marker expression and angiogenesis as potential molecular links. These proteins, often described in separate biological contexts or diseases, include AURKA and AURKB, CHGA, CREB1, EZH2, FOXA2, GRK3, HIF1, IL-6, MYCN, ONECUT2, p53, RET, and RB1. We also present the current efforts in prostate cancer or other diseases to target some of these proteins, which warrants testing for NEPC, given the urgent unmet need in treating this aggressive variant of prostate cancer.

Molecular profiling stratifies diverse phenotypes of treatment-refractory metastatic castration-resistant prostate cancer

Metastatic castration-resistant prostate cancer (mCRPC) is a heterogeneous disease with diverse drivers of disease progression and mechanisms of therapeutic resistance. We conducted deep phenotypic characterization of CRPC metastases and patient-derived xenograft (PDX) lines using whole genome RNA sequencing, gene set enrichment analysis and immunohistochemistry. Our analyses revealed five mCRPC phenotypes based on the expression of well-characterized androgen receptor (AR) or neuroendocrine (NE) genes: (i) AR-high tumors (ARPC), (ii) AR-low tumors (ARLPC), (iii) amphicrine tumors composed of cells co-expressing AR and NE genes (AMPC), (iv) double-negative tumors (i.e. AR-/NE-; DNPC) and (v) tumors with small cell or NE gene expression without AR activity (SCNPC). RE1-silencing transcription factor (REST) activity, which suppresses NE gene expression, was lost in AMPC and SCNPC PDX models. However, knockdown of REST in cell lines revealed that attenuated REST activity drives the AMPC phenotype but is not sufficient for SCNPC conversion. We also identified a subtype of DNPC tumors with squamous differentiation and generated an encompassing 26-gene transcriptional signature that distinguished the five mCRPC phenotypes. Together, our data highlight the central role of AR and REST in classifying treatment-resistant mCRPC phenotypes. These molecular classifications could potentially guide future therapeutic studies and clinical trial design.

The number of titrated microRNA species dictates ceRNA regulation

microRNAs (miRNAs) play key roles in cancer, but their propensity to couple their targets as competing endogenous RNAs (ceRNAs) has only recently emerged. Multiple models have studied ceRNA regulation, but these models did not account for the effects of co-regulation by miRNAs with many targets. We modeled ceRNA and simulated its effects using established parameters for miRNA/mRNA interaction kinetics while accounting for co-regulation by multiple miRNAs with many targets. Our simulations suggested that co-regulation by many miRNA species is more likely to produce physiologically relevant context-independent couplings. To test this, we studied the overlap of inferred ceRNA networks from four tumor contexts-our proposed pan-cancer ceRNA interactome (PCI). PCI was composed of interactions between genes that were co-regulated by nearly three-times as many miRNAs as other inferred ceRNA interactions. Evidence from expression-profiling datasets suggested that PCI interactions are predictive of gene expression in 12 independent tumor- and non-tumor contexts. Biochemical assays confirmed ceRNA couplings for two PCI subnetworks, including oncogenes CCND1, HIF1A and HMGA2, and tumor suppressors PTEN, RB1 and TP53. Our results suggest that PCI is enriched for context-independent interactions that are coupled by many miRNA species and are more likely to be context independent.

Development of a microfluidic platform for size-based hydrodynamic enrichment and PSMA-targeted immunomagnetic isolation of circulating tumour cells in prostate cancer

Efforts to further improve the clinical management of prostate cancer (PCa) are hindered by delays in diagnosis of tumours and treatment deficiencies, as well as inaccurate prognoses that lead to unnecessary or inefficient treatments. The quantitative and qualitative analysis of circulating tumour cells (CTCs) may address these issues and could facilitate the selection of effective treatment courses and the discovery of new therapeutic targets. Therefore, there is much interest in isolation of elusive CTCs from blood. We introduce a microfluidic platform composed of a multiorifice flow fractionation (MOFF) filter cascaded to an integrated microfluidic magnetic (IMM) chip. The MOFF filter is primarily employed to enrich immunomagnetically labeled blood samples by size-based hydrodynamic removal of free magnetic beads that must originally be added to samples at disproportionately high concentrations to ensure the efficient immunomagnetic labeling of target cancer cells. The IMM chip is then utilized to capture prostate-specific membrane antigen-immunomagnetically labeled cancer cells from enriched samples. Our preclinical studies showed that the proposed method can selectively capture up to 75% of blood-borne PCa cells at clinically-relevant low concentrations (as low as 5 cells/ml), with the IMM chip showing up to 100% magnetic capture capability.

Fatty Acids and Calcium Regulation in Prostate Cancer

Prostate cancer is a widespread malignancy characterized by a comparative ease of primary diagnosis and difficulty in choosing the individualized course of treatment. Management of prostate cancer would benefit from a clearer understanding of the molecular mechanisms behind the transition to the lethal, late-stage forms of the disease, which could potentially yield new biomarkers for differential prognosis and treatment prioritization in addition to possible new therapeutic targets. Epidemiological research has uncovered a significant correlation of prostate cancer incidence and progression with the intake (and often co-intake) of fatty acids and calcium. Additionally, there is evidence of the impact of these nutrients on intracellular signaling, including the mechanisms mediated by the calcium ion as a second messenger. The present review surveys the recent literature on the molecular mechanisms associated with the critical steps in the prostate cancer progression, with special attention paid to the regulation of these processes by fatty acids and calcium homeostasis. Testable hypotheses are put forward that integrate some of the recent results in a more unified picture of these phenomena at the interface of cell signaling and metabolism.

CXCL12γ Promotes Metastatic Castration-Resistant Prostate Cancer by Inducing Cancer Stem Cell and Neuroendocrine Phenotypes

There is evidence that cancer stem-like cells (CSC) and neuroendocrine behavior play critical roles in the pathogenesis and clinical course of metastatic castration-resistant prostate cancer (m-CRPC). However, there is limited mechanistic understanding of how CSC and neuroendocrine phenotypes impact the development of m-CRPC. In this study, we explored the role of the intracellular chemokine CXCL12γ in CSC induction and neuroendocrine differentiation and its impact on m-CRPC. CXCL12γ expression was detected in small-cell carcinoma of metastatic tissues and circulating tumor cells from m-CRPC patients and in prostate cancer cells displaying an neuroendocrine phenotype. Mechanistic investigations demonstrated that overexpression of CXCL12γ induced CSC and neuroendocrine phenotypes in prostate cancer cells through CXCR4-mediated PKCα/NFκB signaling, which promoted prostate tumor outgrowth, metastasis, and chemoresistance in vivo Together, our results establish a significant function for CXCL12γ in m-CRPC development and suggest it as a candidate therapeutic target to control aggressive disease.Significance: Expression of CXCL12γ induces the expression of a cancer stem cell and neuroendocrine phenotypes, resulting in the development of aggressive m-CRPC. Cancer Res; 78(8); 2026-39. ©2018 AACR.

Reduction of two histone marks, H3k9me3 and H3k27me3 by epidrug induces neuroendocrine differentiation in prostate cancer

Neuroendocrine prostate cancer (NE PCa) is an aggressive malignancy, often presenting with advanced metastasis. We previously reported that reduction of histone marks regulated by DNMT1 following epidrug (5-Azacitidine, 5-Aza) treatment controls induction of epithelial to mesenchymal (EMT) and a cancer stem cell (CSC) phenotype, which facilitates tumorigenesis in PCa cells. Here, we use the epidrug 5-Aza as a model for how histone marks may regulate the reprogramming of prostate adenocarcinoma into NE phenotypic cells. First, we observed that 5-Aza treatment of PCa cells in vitro induces a neuron-like phenotype. In addition, significant increases in the expression of the NE markers N-Myc downstream regulated gene 1 (NDRG1), enolase-2 (ENO2), and synaptophysin were observed. Critically, a high density of NE cells with synaptophysin expression was found in tumors generated by 5-Aza pretreatment of PCa cells. Importantly, induction of NE differentiation of PCa cells was associated with an enhancement of NDRG1 expression by reduction of two histone marks, H3K9me3 and H3K27me3. Further, more NDRG1 expression was detected in the subset of PCa cells with reduced expression of H3K9me3 or H3K27me3 in the tumors generated by 5-Aza pretreated PCa cells and critically, these biological differences are also observed in small cell carcinoma in advanced stage of human primary PCa tumors. Our results suggest that reduction of histone marks regulated by the epidrug 5-Aza may control induction of a NE phenotype, which facilitates PCa progression. These studies suggest a strong rationale for developing therapeutics, which target epigenetic regulation.

Molecular determinants of prostate cancer metastasis

Metastatic cancer remains largely incurable and fatal. The general course of cancer, from the initiation of primary tumor formation and progression to metastasis, is a multistep process wherein tumor cells at each step must display specific phenotypic features. Distinctive capabilities required for primary tumor initiation and growth form the foundation, and sometimes may remain critical, for subsequent metastases. These phenotypic features must remain easily malleable during the acquisition of additional capabilities unique and essential to the metastatic process such as dissemination to distant tissues wherein tumor cells interact with foreign microenvironments. Thus, the metastatic phenotype is a culmination of multiple genetic and epigenetic alterations and subsequent selection for favorable traits under the pressure of ever-changing tumor microenvironments. Although our understanding of the molecular programs that drive cancer metastasis are incomplete, increasing evidence suggests that successful metastatic colonization relies on the dissemination of cancer stem cells (CSCs) with tumor-regenerating capacity and adaptive programs for survival in distant organs. In the past 2-3 years, a myriad of novel molecular regulators and determinants of prostate cancer metastasis have been reported, and in this Perspective, we comprehensively review this body of literature and summarize recent findings regarding cell autonomous molecular mechanisms critical for prostate cancer metastasis.

Retinoblastoma protein (Rb) links hypoxia to altered mechanical properties in cancer cells as measured by an optical tweezer

Hypoxia modulates actin organization via multiple pathways. Analyzing the effect of hypoxia on the biophysical properties of cancer cells is beneficial for studying modulatory signalling pathways by quantifying cytoskeleton rearrangements. We have characterized the biophysical properties of human LNCaP prostate cancer cells that occur in response to loss of the retinoblastoma protein (Rb) under hypoxic stress using an oscillating optical tweezer. Hypoxia and Rb-loss increased cell stiffness in a fashion that was dependent on activation of the extracellular signal-regulated kinase (ERK) and the protein kinase B (AKT)- mammalian target of rapamycin (MTOR) pathways. Pharmacological inhibition of MEK1/2, AKT or MTOR impeded hypoxia-inducible changes in the actin cytoskeleton and inhibited cell migration in Rb-deficient cells conditioned with hypoxia. These results suggest that loss of Rb in transformed hypoxic cancer cells affects MEK1/2-ERK/AKT-MTOR signalling and promotes motility. Thus, the mechanical characterization of cancer cells using an optical tweezer provides an additional technique for cancer diagnosis/prognosis and evaluating therapeutic performance.

Relationship between the expression of CD133, HIF-1α, VEGF and the proliferation and apoptosis in hypoxic human prostate cancer cells

This study measured the levels of expression of CD133, hypoxia-inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF) in human prostate cancer cells grown under hypoxic and non-hypoxic conditions to compare the values to resulting amounts of proliferation and apoptosis in the cells. Human prostate cancer cell line LNCaP cells were routinely thawed, cultured and passaged. Actively growing cells were divided into batches. Cells in the control group were grown under 5% CO₂ + 20% O₂, and those in the hypoxia group were grown under 5% CO₂ + 1% O₂. The experiments were performed after 12, 24 and 72 h under each growth condition. The percentages of CD13⁺ cells were detected by flow cytometry, the expression of HIF-1α and VEGF was detected by western blot analysis, the cell proliferation rate was detected by the MTT assay, and the apoptotic rate was detected by flow cytometry. The results showed that the percentage of CD133⁺ cells, and the expressions of HIF-1α and VEGF for the cells in the hypoxia group increased gradually from 12 to 24, to 72 h, while there were no equivalent changes in the control group. Cell proliferation in the two groups increased gradually from 12 to 24, to 72 h, but was significantly higher at all time-points in the hypoxia group (p<0.05). There was no significant difference in terms of the amount of apoptotic cells at any of the three different time-points in either group, but the apoptotic cells in the hypoxia group were significantly less than those in the control group at each time-point, and the difference was statistically significant (p<0.05). We conclude that the expression of CD133⁺, HIF-1α and VEGF in human prostate cancer cells is related to conditions of hypoxia, which ultimately promotes the proliferation and reduces apoptosis in these cells.

HPV-associated differential regulation of tumor metabolism in oropharyngeal head and neck cancer

HPV-positive oropharyngeal cancer patients experience significantly lower locoregional recurrence and higher overall survival in comparison with HPV-negative patients, especially among those who received radiation therapy. The goal of the present study is to investigate the molecular mechanisms underlying the differential radiation sensitivity between HPV-negative and HPV-positive head and neck squamous cell carcinoma (HNSCC). Here, we show that HPV-negative HNSCC cells exhibit increased glucose metabolism as evidenced by increased production of lactate, while HPV-positive HNSCC cells effectively utilize mitochondrial respiration as evidenced by increased oxygen consumption. HPV-negative cells express HIF1α and its downstream mediators of glucose metabolism such as hexokinase II (HKII) and carbonic anhydrase IX (CAIX) at higher levels, while the expression level of cytochrome c oxidase (COX) was noticeably higher in HPV-positive HNSCC. In addition, the expression levels of pyruvate dehydrogenase kinases (PDKs), which inhibit pyruvate dehydrogenase activity, thereby preventing entry of pyruvate into the mitochondrial tricarboxylic acid (TCA) cycle, were much higher in HPV-negative HNSCC compared to those in HPV-positive cells. Importantly, a PDK inhibitor, dichloroacetate, effectively sensitized HPV-negative cells to irradiation. Lastly, we found positive interactions between tonsil location and HPV positivity for COX intensity and COX/HKII index ratio as determined by immunohistochemical analysis. Overall survival of patients with HNSCC at the tonsil was significantly improved with an increased COX expression. Taken together, the present study provides molecular insights into the mechanistic basis for the differential responses to radiotherapy between HPV-driven vs. spontaneous or chemically induced oropharyngeal cancer.