Intratumoral Hypoxia as the Genesis of Genetic Instability and Clinical Prognosis in Prostate Cancer

Tumour hypoxia in driving genomic instability and tumour evolution

Intratumour hypoxia is a feature of all heterogenous solid tumours. Increased levels or subregions of tumour hypoxia are associated with an adverse clinical prognosis, particularly when this co-occurs with genomic instability. Experimental evidence points to the acquisition of DNA and chromosomal alterations in proliferating hypoxic cells secondary to inhibition of DNA repair pathways such as homologous recombination, base excision repair and mismatch repair. Cell adaptation and selection in repair-deficient cells give rise to a model whereby novel single-nucleotide mutations, structural variants and copy number alterations coexist with altered mitotic control to drive chromosomal instability and aneuploidy. Whole-genome sequencing studies support the concept that hypoxia is a critical microenvironmental cofactor alongside the driver mutations in MYC, BCL2, TP53 and PTEN in determining clonal and subclonal evolution in multiple tumour types. We propose that the hypoxic tumour microenvironment selects for unstable tumour clones which survive, propagate and metastasize under reduced immune surveillance. These aggressive features of hypoxic tumour cells underpin resistance to local and systemic therapies and unfavourable outcomes for patients with cancer. Possible ways to counter the effects of hypoxia to block tumour evolution and improve treatment outcomes are described.

Intermediate risk prostate tumors contain lethal subtypes

In 2024, prostate cancer (PCa) remains the most common non-skin cancer in males within the United States, with an estimated 299,010 new cases, the highest increase incident trend rate (3.8%) of all cancers, and one of the eight deadliest. PCa cases are projected to double from 1.8 million to 2.9 million per year between 2020 and 2040. According to the National Comprehensive Cancer Network (NCCN) treatment guidelines, most cases (65%) are intermediate risk (Gleason sum score <7 [3 + 4, 4 + 3], prostate organ-confined, and PSA < 20) with treatment options limited to active surveillance, external beam radiation, and/or surgery to prevent metastasis in the long term (>10 years). It is increasingly recognized that the two most common subtypes of intermediate risk PCa are cribriform architecture (CA) and intraductal carcinoma of the prostate (IDC-P), which can occur together, and both are associated with increased metastatic risk, biochemical recurrence, and disease-specific mortality. Both subtypes display hypoxia, genomic instability, and are identified as Gleason 4 in pathology reports. However, since false negatives are common (up to 50%) in these subtypes on biopsy, more research is needed to reliably detect these subtypes that have an increased risk for invasive disease. We note that even with mpMRI-guided biopsies, the sensitivity is 54% for cribriform architecture and only 37% for IDC-P. The presence of these PCa subtypes in biopsy or radical prostatectomy (RP) tissue can exclude patients from active surveillance and from designation as intermediate risk disease, further underscoring the need for increased molecular understanding of these subtypes for diagnostic purposes. Understanding the heterogeneity of intermediate risk primary PCa phenotypes, using computational pathology approaches to evaluate the fixed biopsy specimen, or video microscopy of the surgical specimen with AI-driven analysis is now achievable. New research associating the resulting phenotypes with the different therapeutic choices and vulnerabilities will likely prevent extracapsular extension, the definition of high-risk disease, and upstaging of the final pathologic stage.

Application of radiomics in lung immuno-oncology

Radiomics is a rapidly evolving field of research that extracts and analyzes quantitative features within medical images. Those features are termed as radiomic features that can characterize a tumor in a comprehensive and quantitative manner with regard to its internal structure and heterogeneity. Radiomic features can be used, alone or in combination with demographic, histological, genomic, or proteomic data, for predicting prognosis or treatment response. Immunotherapy, or immune-oncology, is the study of cancer treatment by taking advantage of the body's immune system to prevent, control, and eliminate cancer. In this review, we first provide a brief introduction to both radiomics and immune-oncology in lung cancer. Then, we discuss the need for developing immune-oncology biomarkers, and the advantages of radiomics in identifying biomarkers related to immunotherapy. We also discuss potential areas in and out of tumors, such as the intra-tumoral hypoxic region and tumor microenvironment, where radiomic markers might be extracted, as well as a potential application of radiomic biomarkers in clinical lung cancer management. Finally, we present radiation and immune modulation in non-small cell lung cancer, clinical trials and their design to incorporate radiomic biomarkers, and radiomics-guided precision radiation therapy.

Hypoxia Activates Notch4 via ERK/JNK/P38 MAPK Signaling Pathways to Promote Lung Adenocarcinoma Progression and Metastasis

Hypoxia contributes to the progression and metastasis of lung adenocarcinoma (LUAD). However, the specific underlying molecular mechanisms have not been fully elucidated. Here we report that Notch4 is upregulated in lung tissue from lung cancer patients. Functionally, Hypoxia activates the expressions of Delta-like 4 and Notch4, resulting in the excessive proliferation and migration of LUAD cells as well as apoptotic resistance. Notch4 silencing reduced ERK, JNK, and P38 activation. Meanwhile, Notch4 overexpression enhanced ERK, JNK, and P38 activation in LUAD cells. Furthermore, Notch4 exerted pro-proliferation, anti-apoptosis and pro-migration effects on LUAD cells that were partly reversed by the inhibitors of ERK, JNK, and p38. The binding interaction between Notch4 and ERK/JNK/P38 were confirmed by the co-immunoprecipitation assay. In vivo study revealed that Notch4 played a key role in the growth and metastasis of LUAD using two xenograft models. This study demonstrates that hypoxia activates Notch4-ERK/JNK/P38 MAPK signaling pathways to promote LUAD cell progression and metastasis.

Clinical and functional characterization of CXCR1/CXCR2 biology in the relapse and radiotherapy resistance of primary PTEN-deficient prostate carcinoma

Functional impairment of the tumour suppressor PTEN is common in primary prostate cancer and has been linked to relapse post-radiotherapy (post-RT). Pre-clinical modelling supports elevated CXC chemokine signalling as a critical mediator of PTEN-depleted disease progression and therapeutic resistance. We assessed the correlation of PTEN deficiency with CXC chemokine signalling and its association with clinical outcomes. Gene expression analysis characterized a PTEN ^LOW/CXCR1^HIGH/CXCR2^HIGH cluster of tumours that associates with earlier time to biochemical recurrence [hazard ratio (HR) 5.87 and 2.65, respectively] and development of systemic metastasis (HR 3.51). In vitro, CXCL signalling was further amplified following exposure of PTEN-deficient prostate cancer cell lines to ionizing radiation (IR). Inhibition of CXCR1/2 signalling in PTEN-depleted cell-based models increased IR sensitivity. In vivo, administration of a CXCR1/2-targeted pepducin (x1/2pal-i3), or CXCR2-specific antagonist (AZD5069), in combination with IR to PTEN-deficient xenografts attenuated tumour growth and progression compared to control or IR alone. Post-mortem analysis confirmed that x1/2pal-i3 administration attenuated IR-induced CXCL signalling and anti-apoptotic protein expression. Interventions targeting CXC chemokine signalling may provide an effective strategy to combine with RT in locally advanced prostate cancer patients with known presence of PTEN-deficient foci.

miR-210 is induced by hypoxia and regulates neural cell adhesion molecule in prostate cells

Hypoxia in prostate tumours has been associated with disease progression and metastasis. MicroRNAs are short noncoding RNA molecules that are important in several cell processes, but their role in hypoxic signalling is still poorly understood. miR-210 has been linked with hypoxic mechanisms, but this relationship has been poorly characterised in prostate cancer. In this report, the link between hypoxia and miR-210 in prostate cancer cells is investigated. Polymerase chain reaction analysis demonstrates that miR-210 is induced by hypoxia in prostate cancer cells using in vitro cell models and an in vivo prostate tumour xenograft model. Analysis of The Cancer Genome Atlas prostate biopsy datasets shows that miR-210 is significantly correlated with Gleason grade and other clinical markers of prostate cancer progression. Neural cell adhesion molecule (NCAM) is identified as a target of miR-210, providing a biological mechanism whereby hypoxia-induced miR-210 expression can contribute to prostate cancer. This study provides evidence that miR-210 is an important regulator of cell response to hypoxic stress and proposes that its regulation of NCAM may play an important role in the pathogenesis of prostate cancer.

Prediction of the Prognosis Based on Chromosomal Instability-Related DNA Methylation Patterns of ELOVL2 and UBAC2 in PTCs

Papillary thyroid carcinoma (PTC) is the most common malignant tumor of endocrine systems. Chromosomal instability (CIN) is crucial to the clinical prognoses of tumor patients. DNA methylation plays an important role in the regulation of gene expression and CIN. Based on PTC samples from The Cancer Genome Atlas database, we used multiple regression analyses to identify methylation patterns of CpG sites with the strongest correlation with gene expression. A total of 4,997 genes were obtained through combining the CpG sites, which were represented as featured DNA methylation patterns. In order to identify CIN-related epigenetic markers of PTC survival, we developed a method to characterize CIN based on DNA methylation patterns of genes using the Student’s t statistics. We found that 1,239 genes were highly associated with CIN. With the use of the log-rank test, univariate Cox regression analyses, and the Kaplan-Meier method, DNA methylation patterns of UBAC2 and ELOVL2, highly correlated with CIN, provided potential prognostic values for PTC. The higher these two genes, risk scores were correlated with worse PTC patient prognoses. Moreover, the ELOVL2 risk score was significantly different in the four stages of PTC, suggesting that it was related to the progress of PTC. The DNA methylation pattern associated with CIN may therefore be a good predictor of PTC survival.

Prolyl hydroxylase domain 3 influences the radiotherapy efficacy of pancreatic cancer cells by targeting hypoxia-inducible factor-1α

PURPOSE

Pancreatic cancer is characterized by a hypoxic microenvironment and resistance to most currently available treatment modalities. Prolyl hydroxylase domain 3 (PHD3) is a rate-limiting enzyme that regulates the degradation of hypoxia-inducible factors (HIFs) and is deregulated in pancreatic cancer cells. Whether such alteration of PHD3 expression contributes to the sustained growth and radioresistance of pancreatic cancer cells remains largely unknown.

MATERIALS AND METHODS

PHD3 was overexpressed in pancreatic cancer Mia-paca2 cells via lentiviral expression. Cell cycle progression and apoptosis were assayed by flow cytometry. HIF-1α, EGFR, and PHD3 protein expression was assessed by Western blotting. Cell survival was determined in a colony formation assay.

RESULTS

PHD3 overexpression suppressed HIF-1α protein expression and EGFR phosphorylation and enhanced the 2 Gy irradiation-mediated reductions in HIF-1α and phosphorylated (p)-EGFR under either normoxic or hypoxic conditions. PHD3 overexpression inhibited the growth and colony formation of Mia-paca2 cells in response to irradiation under either normoxic or hypoxic conditions. PHD3 overexpression exacerbated irradiation-induced apoptosis, with a greater effect under hypoxia than normoxia. Cell cycle distribution analysis demonstrated that PHD3 overexpression resulted in further shortened S phase and lengthened G2/M phase in response to irradiation.

CONCLUSION

PHD3 expression may contribute to the radiotherapy efficacy of pancreatic cancer cells and serve as a novel biomarker for improving radiotherapy efficacy in pancreatic cancer.

Evaluation of tumor hypoxia prior to radiotherapy in intermediate-risk prostate cancer using 18F-fluoromisonidazole PET/CT: a pilot study

Purpose

Hypoxia is a major factor in prostate cancer aggressiveness and radioresistance. Predicting which patients might be bad candidates for radiotherapy may help better personalize treatment decisions in intermediate-risk prostate cancer patients. We assessed spatial distribution of ¹⁸F-Misonidazole (FMISO) PET/CT uptake in the prostate prior to radiotherapy treatment.

Materials and Methods

Intermediate-risk prostate cancer patients about to receive high-dose (>74 Gy) radiotherapy to the prostate without hormonal treatment were prospectively recruited between 9/2012 and 10/2014. Prior to radiotherapy, all patients underwent a FMISO PET/CT as well as a MRI and ¹⁸F-choline-PET. ¹⁸F-choline and FMISO-positive volumes were semi-automatically determined using the fuzzy locally adaptive Bayesian (FLAB) method. In FMISO-positive patients, a dynamic analysis of early tumor uptake was performed. Group differences were assessed using the Wilcoxon signed rank test. Parameters were correlated using Spearman rank correlation.

Results

Of 27 patients (median age 76) recruited to the study, 7 and 9 patients were considered positive at 2.5h and 3.5h FMISO PET/CT respectively. Median SUV_max and SUV_max tumor to muscle (T/M) ratio were respectively 3.4 and 3.6 at 2.5h, and 3.2 and 4.4 at 3.5h. The median FMISO-positive volume was 1.1 ml.

Conclusions

This is the first study regarding hypoxia imaging using FMISO in prostate cancer showing that a small FMISO-positive volume was detected in one third of intermediate-risk prostate cancer patients.

The unidirectional hypoxia-activated prodrug OCT1002 inhibits growth and vascular development in castrate-resistant prostate tumors

BACKGROUND

OCT1002 is a unidirectional hypoxia-activated prodrug (uHAP) OCT1002 that can target hypoxic tumor cells. Hypoxia is a common feature in prostate tumors and is known to drive disease progression and metastasis. It is, therefore, a rational therapeutic strategy to directly target hypoxic tumor cells in an attempt to improve treatment for this disease. Here we tested OCT1002 alone and in combination with standard-of-care agents in hypoxic models of castrate-resistant prostate cancer (CRPC).

METHODS

The effect of OCT1002 on tumor growth and vasculature was measured using murine PC3 xenograft and dorsal skin fold (DSF) window chamber models. The effects of abiraterone, docetaxel, and cabazitaxel, both singly and in combination with OCT1002, were also compared.

RESULTS

The hypoxia-targeting ability of OCT1002 effectively controls PC3 tumor growth. The effect was evident for at least 42 days after exposure to a single dose (30 mg/kg) and was comparable to, or better than, drugs currently used in the clinic. In DSF experiments OCT1002 caused vascular collapse in the PC3 tumors and inhibited the revascularization seen in controls. In this model OCT1002 also enhanced the anti-tumor effects of abiraterone, cabazitaxel, and docetaxel; an effect which was accompanied by a more prolonged reduction in tumor vasculature density.

CONCLUSIONS

These studies provide the first evidence that OCT1002 can be an effective agent in treating hypoxic, castrate-resistant prostate tumors, either singly or in combination with established chemotherapeutics for prostate cancer.

Exosomes and Exosomal MicroRNAs in Prostate Cancer Radiation Therapy

Despite current risk stratification systems using traditional clinicopathologic factors, many localized and locally advanced prostate cancers fail radical treatment (ie, radical prostatectomy, radiation therapy with or without androgen deprivation therapy). Therefore, a pressing need exists for enhanced methods of disease stratification through novel prognostic and predictive tools that can reliably be applied in clinical practice. Exosomes are 50- to 150-nm small vesicles released by cancer cells that reflect the genetic and nongenetic materials of parent cancer cells. Cancer cells can contain distinct sets of microRNA profiles, the expression of which can change owing to stress such as radiation therapy. These alterations or distinctions in contents allow exosomes to be used as prognostic and/or predictive biomarkers and to monitor the treatment response. Additionally, microRNAs have been shown to influence multiple processes in prostate tumorigenesis, including cell proliferation, induction of apoptosis, migration, oncogene inhibition, and radioresistance. Thus, comparative exosomal microRNA profiling at different levels could help portray tumor aggressiveness and response to radiation therapy. Although technical challenges persist in exosome isolation and characterization, recent improvements in microRNA profiling have evolved toward in-depth analyses of the exosomal cargo and its functions. We have reviewed the role of exosomes and exosomal microRNAs in biologic processes of prostate cancer progression and radiation therapy response, with a particular focus on the development of clinical assays for treatment personalization.

Cancer stem cells: Radioresistance, prediction of radiotherapy outcome and specific targets for combined treatments

Inactivation of cancer stem cells (CSCs) is of utmost importance for tumor cure after radiotherapy. An increasing body of evidence complies with a higher radioresistance of CSCs compared to the mass of tumor cells, supporting the use of CSC related biomarkers for prediction of radiotherapy outcome. Treatment individualization strategies for patient groups with vastly different risk of recurrence will most likely require application of more than one biomarker. Specifically, inclusion of established biomarkers like tumor size for primary radio(chemo)therapy or human papilloma virus (HPV) infection status in head and neck squamous cell carcinoma seems to be of very high relevance. The high heterogeneity of CSC subclones along with changes of the functional behavior of individual tumors under treatment underlines the importance of the selection of the optimal timepoint(s) of biomarker evaluation, but also provides a potential therapeutic target for combined treatment approaches with irradiation.

Targeting Hypoxic Prostate Tumors Using the Novel Hypoxia-Activated Prodrug OCT1002 Inhibits Expression of Genes Associated with Malignant Progression

Purpose: To understand the role of hypoxia in prostate tumor progression and to evaluate the ability of the novel unidirectional hypoxia-activated prodrug OCT1002 to enhance the antitumor effect of bicalutamide.Experimental Design: The effect of OCT1002 on prostate cancer cells (LNCaP, 22Rv1, and PC3) was measured in normoxia and hypoxia in vitroIn vivo, tumor growth and lung metastases were measured in mice treated with bicalutamide, OCT1002, or a combination. Dorsal skin fold chambers were used to image tumor vasculature in vivo Longitudinal gene expression changes in tumors were analyzed using PCR.Results: Reduction of OCT1002 to its active form (OCT1001) decreased prostate cancer cell viability. In LNCaP-luc spheroids, OCT1002 caused increased apoptosis and decreased clonogenicity. In vivo, treatment with OCT1002 alone, or with bicalutamide, showed significantly greater tumor growth control and reduced lung metastases compared with controls. Reestablishment of the tumor microvasculature following bicalutamide-induced vascular collapse is inhibited by OCT1002. Significantly, the upregulation of RUNX2 and its targets caused by bicalutamide alone was blocked by OCT1002.Conclusions: OCT1002 selectively targets hypoxic tumor cells and enhances the antitumor efficacy of bicalutamide. Furthermore, bicalutamide caused changes in gene expression, which indicated progression to a more malignant genotype; OCT1002 blocked these effects, emphasizing that more attention should be attached to understanding genetic changes that may occur during treatment. Early targeting of hypoxic cells with OCT1002 can provide a means of inhibiting prostate tumor growth and malignant progression. This is of importance for the design and refinement of existing androgen-deprivation regimens in the clinic. Clin Cancer Res; 23(7); 1797-808. ©2016 AACR.

The changing paradigm of tumour response to irradiation

Tumours contain multiple different cell populations, including cells derived from the bone marrow as well as cancer-associated fibroblasts and various stromal populations including the vasculature. The microenvironment of the tumour cells plays a significant role in the response of the tumour to radiation treatment. Low levels of oxygen (hypoxia) caused by the poorly organized vasculature in tumours have long been known to affect radiation response; however, other aspects of the microenvironment may also play important roles. This article reviews some of the old literature concerning tumour response to irradiation and relates this to current concepts about the role of the tumour microenvironment in tumour response to radiation treatment. Included in the discussion are the role of cancer stem cells, radiation damage to the vasculature and the potential for radiation to enhance immune activity against tumour cells. Radiation treatment can cause a significant influx of bone marrow-derived cell populations into both normal tissues and tumours. Potential roles of such cells may include enhancing vascular recovery as well as modulating immune reactivity.

Hypoxia on the Expression of Hepatoma Upregulated Protein in Prostate Cancer Cells

Hepatoma upregulated protein (HURP) is a multifunctional protein with clinical promise. This protein has been demonstrated to be a predictive marker for the outcome in high-risk prostate cancer (PCa) patients, besides being a resistance factor in PCa. Although changes in oxygen tension (pO₂) are associated with PCa aggressiveness, the role of hypoxia in the regulation of tumor progression genes such as HURP has not yet been described. We hypothesized that pO₂ alteration is involved in the regulation of HURP expression in PCa cells. In the present study, PCa cells were incubated at 2% O₂ (hypoxia) and 20% O₂ (normoxia) conditions. Hypoxia reduced cell growth rate of PCa cells, when compared to the growth rate of cells cultured under normoxia (p < 0.05). The decrease in cell viability was accompanied by fivefold (p < 0.05) elevated rate of vascular endothelial growth factor (VEGF) release. The expression of VEGF and the hypoxia-inducible metabolic enzyme carbonic anhydrase 9 were elevated maximally nearly 61-fold and 200-fold, respectively (p < 0.05). Noted in two cell lines (LNCaP and C4-2B) and independent of the oxygen levels, HURP expression assessed at both mRNA and protein levels was reduced. However, the decrease was more pronounced in cells cultured under hypoxia (p < 0.05). Interestingly, the analysis of patients’ specimens by Western blot revealed a marked increase of HURP protein (fivefold), when compared to control (cystoprostatectomy) tissue (p < 0.05). Immunohistochemistry analysis showed an increase in the immunostaining intensity of HURP and the hypoxia-sensitive molecules, hypoxia-inducible factor 1-alpha (HIF-1α), VEGF, and heat-shock protein 60 (HSP60) in association with tumor grade. The data also suggested a redistribution of subcellular localization for HURP and HIF-1α from the nucleus to the cytoplasmic compartment in relation to increasing tumor grade. Analysis of HURP Promoter for HIF-1-binding sites revealed presence of four putative HIF binding sites on the promoter of DLGAP5/HURP gene in the non-translated region upstream from the start codon, suggesting association between HIF-1α and the regulation of HURP protein. Taken together, our findings suggest a modulatory role of hypoxia on the expression of HURP. Additionally our results provide basis for utilization of tumor-associated molecules as predictors of aggressive PCa.

Androgen deprivation in LNCaP prostate tumour xenografts induces vascular changes and hypoxic stress, resulting in promotion of epithelial-to-mesenchymal transition

Background:

When single-agent androgen deprivation therapy (ADT) is administered for locally advanced prostate cancer, men usually relapse within 1–2 years with more malignant castrate-resistant disease. The reason for this is currently unknown. We now hypothesise that an initial treatment response that increases tumour hypoxia drives selection of more malignant tumours.

Methods:

The LNCaP prostate tumour xenografts were analysed for physiological (oxygen and vasculature) and genetic (PCR array) changes during longitudinal treatment with ADT (bicalutamide, 6 or 2 mg kg⁻¹ daily for 28 days).

Results:

Bicalutamide caused an immediate (within 24 h) dose-dependent fall in oxygenation in LNCaP-luc prostate tumours with a nadir of ≤0.1% oxygen within 3–7 days; this was attributed to a significant loss of tumour microvessels (window chamber study). The hypoxic nadir persisted for 10–14 days. During the next 7 days, tumours regrew, oxygenation improved and the vasculature recovered; this was inhibited by the VEGF inhibitor B20.4.1.1. Gene expression over 28 days showed marked fluctuations consistent with the physiological changes. Accompanying the angiogenic burst (day 21) was a particularly striking increase in expression of genes associated with epithelial-to-mesenchymal transition (EMT). In particular, insulin-like growth factor 1 (IGF-1) showed increases in mRNA and protein expression.

Conclusions:

Hypoxic stress caused by ADT promotes EMT, providing a mechanism for the cause of malignant progression in prostate cancer.

The clinical significance of hypoxia in human cancers

Hypoxia is present to some extent in most solid malignant human cancers because of an imbalance between the limited oxygen delivery capacity of the abnormal vasculature and the high oxygen consumption of tumor cells. This drives a complex and dynamic compensatory response to enable continued cell survival, including genomic changes leading to selection of hypoxia-adapted cells with a propensity to invade locally, metastasize, and recur following surgery or radiotherapy. There is indisputable clinical evidence from numerous observational and therapeutic studies across a range of tumor types to implicate hypoxia as a key determinant of cancer behavior and treatment outcome. Despite this, hypoxia-targeted treatment has failed to influence clinical practice. This is explained, in part, by emerging findings to indicate that hypoxia is not equally important in all patients even when present to the same extent. The impact of hypoxia on patient outcome and the benefit of hypoxia-targeted treatments are greatest in situations where hypoxia is a primary biological driver of disease behavior-patients with tumors having a "hypoxic driver" phenotype. The challenge for the clinical and scientific communities moving forward is to develop robust precision cancer medicine strategies for identifying these patients in the setting of other etiologic, genomic, and host-tumor factors, considering not only the state of the tumor at diagnosis but also changing patient and tumor characteristics over time.

Effects of oxygen on the antigenic landscape of prostate cancer cells

Background

Use of allogeneic cancer cells-based immunotherapy for treatment of established prostate cancer (PCa) has only been marginally effective. One reason for failure could stem from the mismatch of antigenic signatures of vaccine cells and cancer in situ. Hence, it is possible that vaccine cells expressed antigens differently than tumor cells in situ. We hypothesized that cells grown in vitro at low oxygen tension (pO₂) provide a better antigen match to tumors in situ and could reveal a more relevant antigenic landscape than cells grown in atmospheric pO₂.

Methods

We tested this hypothesis by comparing PCa cells propagated at pO₂ = 2 kPa and 20 kPa. To identify potential tumor-associated antigens (TAAs), we prepared PCa cell lysates, resolved them by two-dimensional electrophoresis and immunoblotting using spontaneous antibodies from plasma derived from PCa patients and control subjects. Antibody-labeled spots were analyzed by MALDI-TOF mass spectrometry and validated by ELISA. We selected hypoxia-regulated HSP70 and hnRNP L and hypoxia-independent HSP60 and determined the frequency of plasma samples reacting with these molecules.

Results

Frequency of HSP60-reactive plasma was low in healthy controls [1.3 % (1/76)], while it was elevated in PCa patients [13.0 % (7/54); p < 0.05]. These data suggest a humoral immune response to HSP60 in PCa. Levels of autoantibodies to HSP70 did not differ from healthy controls [3.7 % (2/54)] in PCa patients [5.3 % (2/38)]. Similarly, hnRNP L autoantibodies did no differ between healthy controls [6.1 % (3/49)] and PCa patients [5.3 % (2/38)].

Conclusions

Overall our results suggest the value of hypoxia as a modifier of the cellular and antigenic landscape of PCa cells. By modifying the immune reactivity of PCa cells in culture, manipulation of pO₂ can be proposed as a new avenue for improving diagnosis, prognosis and immunotherapy for PCa.

Cell Death Conversion under Hypoxic Condition in Tumor Development and Therapy

Hypoxia, which is common during tumor progression, plays important roles in tumor biology. Failure in cell death in response to hypoxia contributes to progression and metastasis of tumors. On the one hand, the metabolic and oxidative stress following hypoxia could lead to cell death by triggering signal cascades, like LKB1/AMPK, PI3K/AKT/mTOR, and altering the levels of effective components, such as the Bcl-2 family, Atg and p62. On the other hand, hypoxia-induced autophagy can serve as a mechanism to turn over nutrients, so as to mitigate the adverse condition and then avoid cell death potentially. Due to the effective role of hypoxia, this review focuses on the crosstalk in cell death under hypoxia in tumor progression. Additionally, the illumination of cell death in hypoxia could shed light on the clinical applications of cell death targeted therapy.

Upregulation of fractalkine contributes to the proliferative response of prostate cancer cells to hypoxia via promoting the G1/S phase transition

Hypoxia is a common phenomenon in prostate cancer, which leads to cell proliferation and tumor growth. Fractalkine (FKN) is a membrane-bound chemokine, which is implicated in the progression of human prostate cancer and skeletal metastasis. However, the association between FKN and hypoxia-induced prostate cancer cell proliferation remains to be elucidated. The present study demonstrated that hypoxia induced the expression and secretion of FKN in the DU145 prostate cancer cell line. Furthermore, inhibiting the activity of FKN with the anti-FKN FKN-specific antibody markedly inhibited hypoxia-induced DU145 cell proliferation. Under normoxic conditions, DU145 cell proliferation markedly increased following exogenous administration of human recombinant FKN protein, and the increase was significantly alleviated by anti-FKN, indicating the importance of FKN in DU145 cell proliferation. In addition, subsequent determination of cell cycle distribution and expression levels of two core cell cycle regulators, cyclin E and cyclin-dependent kinase (CDK)2, suggested that FKN promoted the G₁/S phase transition by upregulating the expression levels of cyclin E and CDK2. The results of the present study demonstrated that hypoxia led to the upregulation of the secretion and expression of FKN, which enhanced cell proliferation by promoting cell cycle progression in the prostate cancer cells. These findings provide evidence of a novel function for FKN, and suggest that FKN may serve as a potential target for treating androgen-independent prostate cancer.

A cell-based high-throughput screening assay for radiation susceptibility using automated cell counting

Background

Radiotherapy is one of the mainstays in the treatment for cancer, but its success can be limited due to inherent or acquired resistance. Mechanisms underlying radioresistance in various cancers are poorly understood and available radiosensitizers have shown only modest clinical benefit. There is thus a need to identify new targets and drugs for more effective sensitization of cancer cells to irradiation. Compound and RNA interference high-throughput screening technologies allow comprehensive enterprises to identify new agents and targets for radiosensitization. However, the gold standard assay to investigate radiosensitivity of cancer cells in vitro, the colony formation assay (CFA), is unsuitable for high-throughput screening.

Methods

We developed a new high-throughput screening method for determining radiation susceptibility. Fast and uniform irradiation of batches up to 30 microplates was achieved using a Perspex container and a clinically employed linear accelerator. The readout was done by automated counting of fluorescently stained nuclei using the Acumen eX3 laser scanning cytometer. Assay performance was compared to that of the CFA and the CellTiter-Blue homogeneous uniform-well cell viability assay. The assay was validated in a whole-genome siRNA library screening setting using PC-3 prostate cancer cells.

Results

On 4 different cancer cell lines, the automated cell counting assay produced radiation dose response curves that followed a linear-quadratic equation and that exhibited a better correlation to the results of the CFA than did the cell viability assay. Moreover, the cell counting assay could be used to detect radiosensitization by silencing DNA-PKcs or by adding caffeine. In a high-throughput screening setting, using 4 Gy irradiated and control PC-3 cells, the effects of DNA-PKcs siRNA and non-targeting control siRNA could be clearly discriminated.

Conclusions

We developed a simple assay for radiation susceptibility that can be used for high-throughput screening. This will aid the identification of molecular targets for radiosensitization, thereby contributing to improving the efficacy of radiotherapy.

Is carbonic anhydrase IX a validated target for molecular imaging of cancer and hypoxia?

The presence of hypoxia is a general feature of most solid malignancies, and hypoxia is considered as one of major factors for anticancer therapy failure. Carbonic anhydrase IX (CAIX) has been reported to be an endogenous hypoxia marker, CAIX monoclonal antibodies, their segments and inhibitors are developed for CAIX imaging. However, growing evidence indicates that CAIX expression under hypoxia condition may be cancer cell lines or cancer-type dependent. Here we review the current literature on CAIX and discuss the advantage and limitation of CAIX as a target for tumor hypoxia imaging. Accordingly, CAIX would be unreliable as a universal target for cancer and tumor hypoxia visualization.

Biphasic regulation of autophagy by miR-96 in prostate cancer cells under hypoxia

Autophagy favors cell survival under hypoxia, and increasing evidence revealed that microRNAs regulate autophagy. We report here hypoxia increased the expression of miR-96 in prostate cancer cells, and miR-96 stimulated autophagy by suppressing MTOR. We found that inhibition of miR-96 abolished hypoxia-induced autophagy. Paradoxically, ectopic over-expression of miR-96 to a certain threshold, also abolished the hypoxia-induced autophagy. Further studies have shown that high levels of miR-96 inhibited autophagy through suppressing ATG7, a key autophagy-associated gene. Importantly, the miR-96 expression level threshold was determined, and the effects of miR-96 on autophagy on either side of the threshold were opposite. These data demonstrate hypoxia-induced autophagy is at least partially regulated by miR-96; miR-96 can promote or inhibit autophagy by principally inhibiting MTOR or ATG7 depending on the expression levels of miR-96. Our observation might reveal a novel regulatory mode of autophagy by microRNAs under hypoxia.