PHD1 regulates p53-mediated colorectal cancer chemoresistance

The combination of SHP099 inhibits the malignant biological behavior of L-OHP/5-FU-resistant colorectal cancer cells by regulating energy metabolism reprogramming

BACKGROUND AND OBJECTIVE

Colorectal cancer (CRC) is one of the most common malignancies in China. At present, there is a problem that the CRC treatment drugs SHP099, L-OHP and 5-FU are insensitive to tumor cells. Combination medication is an important means to solve the insensitivity of medication alone. The purpose of this project was to explore the effect and molecular mechanism of SHP099 combination on the malignant biological behavior of L-OHP/5-FU resistant strains of CRC.

METHODS

HT29 and SW480 cells were cultured in media supplemented with L-OHP or 5-FU to establish drug-resistant strains. HT29 and SW480 drug-resistant cells were subcutaneously injected into the ventral nerves of nude mice at a dose of 5 × 106 to establish CRC drug-resistant animal models. CCK-8, Western blot, flow cytometry, Transwell and kit detection were used to detect the regulatory mechanism of energy metabolism reprogramming in drug-resistant CRC cells.

RESULTS

Compared with nonresistant strains, L-OHP/5-FU-resistant strains exhibited greater metabolic reprogramming. Functionally, SHP099 can restrain the metabolic reprogramming of L-OHP/5-FU-resistant strains and subsequently restrain the proliferation, colony formation, migration and spheroid formation of L-OHP/5-FU-resistant strains. Downstream mechanistic studies have shown that SHP099 interferes with the metabolic reprogramming of L-OHP/5-FU drug-resistant strains by suppressing the PI3K/AKT pathway, thereby restraining the malignant biological behavior of L-OHP/5-FU drug-resistant strains and alleviating CRC.

CONCLUSION

The combination of SHP099 can restrain the malignant biological behavior of L-OHP/5-FU-resistant CRC cells and alleviate the progression of CRC by interfering with the reprogramming of energy metabolism. This study explored the effect of SHP099 combination on dual-resistant CRC cells for the first time, and provided a new therapeutic idea for solving the problem of SHP099 insensitivity to CRC cells.

Zebrafish phd1 enhances mavs-mediated antiviral responses in a hydroxylation-independent manner

PHD1 is a member of the prolyl hydroxylase domain protein (PHD1-4) family, which plays a prominent role in the post-translational modification of its target proteins by hydroxylating proline residues. The best-characterized targets of PHD1 are hypoxia-inducible factor α (HIF-1α and HIF-2α), two master regulators of the hypoxia signaling pathway. In this study, we show that zebrafish phd1 positively regulates mavs-mediated antiviral innate immunity. Overexpression of phd1 enhances the cellular antiviral response. Consistently, zebrafish lacking phd1 are more susceptible to spring viremia of carp virus infection. Further assays indicate that phd1 interacts with mavs through the C-terminal transmembrane domain of mavs and promotes mavs aggregation. In addition, zebrafish phd1 attenuates K48-linked polyubiquitination of mavs, leading to stabilization of mavs. However, the enzymatic activity of phd1 is not required for phd1 to activate mavs. In conclusion, this study reveals a novel function of phd1 in the regulation of antiviral innate immunity.IMPORTANCEPHD1 is a key regulator of the hypoxia signaling pathway, but its role in antiviral innate immunity is largely unknown. In this study, we found that zebrafish phd1 enhances cellular antiviral responses in a hydroxylation-independent manner. Phd1 interacts with mavs through the C-terminal transmembrane domain of mavs and promotes mavs aggregation. In addition, phd1 attenuates K48-linked polyubiquitination of mavs, leading to stabilization of mavs. Zebrafish lacking phd1 are more susceptible to spring viremia of carp virus infection. These findings reveal a novel role for phd1 in the regulation of mavs-mediated antiviral innate immunity.

Yin Yang 1 facilitates the activation, inflammation, and extracellular matrix deposition of hepatic stellate cells in hepatic fibrosis

Chronic hepatic diseases often involve fibrosis as a pivotal factor in their progression. This study investigates the regulatory mechanisms of Yin Yang 1 (YY1) in hepatic fibrosis. Our data reveal that YY1 binds to the prolyl hydroxylase domain 1 (PHD1) promoter. Rats treated with carbon tetrachloride (CCl4) display heightened fibrosis in liver tissues, accompanied by increased levels of YY1, PHD1, and the fibrosis marker alpha-smooth muscle actin (α-SMA). Elevated levels of YY1, PHD1, and α-SMA are observed in the liver tissues of CCl4-treated rats, primary hepatic stellate cells (HSCs) isolated from fibrotic liver tissues, and transforming growth factor beta-1 (TGF-β1)-induced HSCs. The human HSC cell line LX-2, upon YY1 overexpression, exhibits enhanced TGF-β1-induced activation, leading to increased expression of extracellular matrix (ECM)-related proteins and inflammatory cytokines. YY1 silencing produces the opposite effect. YY1 exerts a positive regulatory effect on the activation of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway and PHD1 expression. PHD1 silencing rescues the promotion of YY1 in cell activation, ECM-related protein expression, and inflammatory cytokine production in TGF-β1-treated LX-2 cells. Overall, our findings propose a model wherein YY1 facilitates TGF-β1-induced HSC activation, ECM-related protein expression, and inflammatory cytokine production by promoting PHD1 expression and activating the PI3K/AKT signaling pathway. This study positions YY1 as a promising therapeutic target for hepatic fibrosis.

Tumor-suppressive zinc finger protein 24 (ZNF24) sensitizes colorectal cancer cells to 5-fluorouracil by inhibiting the Wnt pathway and activating the p53 signaling

Carcinogenesis and colorectal cancer (CRC) development are associated with dysregulation of various pathways, including Wnt and p53. 5-fluorouracil (5-FU) is a common chemotherapeutic agent for CRC treatment, but its efficacy is restricted by drug resistance. Doxycycline is an orally active tetracycline antibiotic known for its antimicrobial and anticancer cell proliferation activities. This study intends to delineate the potential role of bioinformatically predicted ZNF24 in the 5-FU resistance of CRC cells. The expression of ZNF24 was measured in clinically collected CRC tissues and cells. Afterward, ectopic ZNF24 expression was induced by DOX to evaluate the viability, colony-forming ability and sphere-forming ability of CRC cells. It was found that ZNF24 was validated to be poorly expressed in CRC tissues, and ectopic expression of ZNF24 was revealed to restrict the malignant phenotypes of CRC cells. In addition, restored ZNF24 attenuated 5-FU resistance of CRC cells by inhibiting the Wnt pathway and activating p53 signaling. Furthermore, an inhibitor of Wnt production 2 (IWP-2) treatment was an alternative to ZNF24 up-regulation in sensitizing CRC cells to 5-FU treatment. In conclusion, our results indicate that ZNF24 inhibits 5-FU resistance of CRC cells by suppressing the Wnt pathway and activating p53 signaling, which offers a potential strategy for managing chemoresistance in CRC.

Decreased expression of prolyl hydroxylase 1 is associated with poor prognosis in colorectal cancers

BACKGROUND

Prolyl hydroxylase 1 (PHD1) is a prognostic marker in several cancers.

AIMS AND SCOPES

This study was undertaken to elucidate the clinical relevance of PHD1 in colorectal cancer (CRC) prognosis.

MATERIALS AND METHODS

We compared PHD1 expression on a tissue microarray (TMA) containing samples from 1800 CRCs with corresponding clinicopathological tumor variables and patient survival.

RESULTS

While PHD1 staining was always high in benign colorectal epithelium, high PHD1 staining was detectable in only 71.8% of CRCs. Low PHD1 staining was associated with advanced tumor stage (p = 0.0101) and shortened overall survival in CRC patients (p = 0.0011). In a multivariable analysis including tumor stage, histological type and PHD1 staining revealed tumor stage and histological type (p < 0.0001 each), but also PHD1 staining (p = 0.0202) to be independent prognostic markers for CRC.

CONCLUSIONS

In our cohort, loss of PHD1 expression independently identified a subset of CRC patients with poor overall survival and might, thus, be a promising prognostic marker. PHD1 targeting may even allow for specific therapeutic approaches for these patients.

Searching for molecular hypoxia sensors among oxygen-dependent enzymes

The ability to sense and respond to changes in cellular oxygen levels is critical for aerobic organisms and requires a molecular oxygen sensor. The prototypical sensor is the oxygen-dependent enzyme PHD: hypoxia inhibits its ability to hydroxylate the transcription factor HIF, causing HIF to accumulate and trigger the classic HIF-dependent hypoxia response. A small handful of other oxygen sensors are known, all of which are oxygen-dependent enzymes. However, hundreds of oxygen-dependent enzymes exist among aerobic organisms, raising the possibility that additional sensors remain to be discovered. This review summarizes known and potential hypoxia sensors among human O2-dependent enzymes and highlights their possible roles in hypoxia-related adaptation and diseases.

A Hypoxia Molecular Signature-Based Prognostic Model for Endometrial Cancer Patients

Endometrial cancer has the highest incidence of uterine corpus cancer, the sixth most typical cancer in women until 2020. High recurrence rate and frequent adverse events were reported in either standard chemotherapy or combined therapy. Hence, developing precise diagnostic and prognostic approaches for endometrial cancer was on demand. Four hypoxia-related genes were screened for the EC prognostic model by the univariate, LASSO, and multivariate Cox regression analysis from the TCGA dataset. QT-PCR and functional annotation analysis were performed. Associations between predicted risk and immunotherapy and chemotherapy responses were investigated by evaluating expressions of immune checkpoint inhibitors, infiltrated immune cells, m6a regulators, and drug sensitivity. The ROC curve and calibration plot indicated a fair predictability of our prognostic nomogram model. NR3C1 amplification, along with IL-6 and SRPX suppressions, were detected in tumor. High stromal score and enriched infiltrated aDCs and B cells in the high-risk group supported the hypothesis of immune-deserted tumor. Hypoxia-related molecular subtypes of EC were then identified via the gene signature. Cluster 2 patients showed a significant sensitivity to Vinblastine. In summary, our hypoxia signature model accurately predicted the survival outcome of EC patients and assessed translational and transcriptional dysregulations to explore targets for precise medical treatment.

The multifaceted role of EGLN family prolyl hydroxylases in cancer: going beyond HIF regulation

EGLN1, EGLN2 and EGLN3 are proline hydroxylase whose main function is the regulation of the HIF factors. They work as oxygen sensors and are the main responsible of HIFα subunits degradation in normoxia. Being their activity strictly oxygen-dependent, when oxygen tension lowers, their control on HIFα is released, leading to activation of systemic and cellular response to hypoxia. However, EGLN family members activity is not limited to HIF modulation, but it includes the regulation of essential mechanisms for cell survival, cell cycle metabolism, proliferation and transcription. This is due to their reported hydroxylase activity on a number of non-HIF targets and sometimes to hydroxylase-independent functions. For these reasons, EGLN enzymes appear fundamental for development and progression of different cancer types, playing either a tumor-suppressive or a tumor-promoting role, according to EGLN isoform and to tumor context. Notably, EGLN1, the most studied isoform, has been shown to have also a central role in tumor micro-environment modulation, mediating CAF activation and impairing HIF1α -related angiogenesis, thus covering an important function in cancer metastasis promotion. Considering the recent knowledge acquired on EGLNs, the possibility to target these enzymes for cancer treatment is emerging. However, due to their multifaceted and controversial roles in different cancer types, the use of EGLN inhibitors as anti-cancer drugs should be carefully evaluated in each context.

ATF4-mediated microRNA-145/HDAC4/p53 axis affects resistance of colorectal cancer cells to 5-fluorouracil by regulating autophagy

BACKGROUND

The impact of activating transcription factor 4 (ATF4), differentially expressed in colorectal cancer (CRC), on 5-Fluorouracil (5-FU) chemoresistance has not been fully explained. The purpose of this study is to evaluate the clinical significance of ATF4-mediated microRNA-145 (miR-145)/histone deacetylase 4 (HDAC4)/p53 axis in CRC.

METHODS

Initially, the expression of ATF4, miR-145, HDAC4, and p53 in CRC tissues and cells was quantified by RT-qPCR and immunoblotting. Next, luciferase activity and chromatin immunoprecipitation assays were performed to verify the binding affinity among miR-145, ATF4, and HDAC4. Moreover, proliferation, clone formation, and apoptosis in CRC cells treated with 5-FU were assessed after gain- or loss-of-function of ATF4, miR-145, and/or HDAC4. Furthermore, the tumorigenicity and chemoresistance of CRC cells in mice were assayed for validating the in vitro findings.

RESULTS

ATF4 and HDAC4 were highly expressed, while miR-145 and p53 were poorly expressed in CRC tissues and cells. miR-145 targeted and negatively regulated HDAC4 to activate p53, and miR-145 expression was suppressed by ATF4. Of note, ATF4 facilitated cell proliferation and clone formation ability and repressed apoptosis to promote autophagy and chemoresistance of CRC cells by regulating the miR-145/HDAC4/p53 axis. In vivo experiment elucidated that ATF4-mediated miR-145/HDAC4/p53 axis enhanced tumorigenesis and resistance of CRC cells to 5-FU.

CONCLUSION

In conclusion, ATF4-mediated miR-145 inhibition accelerated autophagy of CRC cells and boosted their resistance to 5-FU via the HDAC4/p53 axis.

EGLN1 induces tumorigenesis and radioresistance in nasopharyngeal carcinoma by promoting ubiquitination of p53 in a hydroxylase-dependent manner

Egl-9 Family Hypoxia Inducible Factor 1 (EGLN1) is a proline hydroxylase mediating degradation of hypoxia-inducible factor α (HIFα) through the ubiquitination system. Studies have indicated an essential role for EGLN1 in angiogenesis and tumorigenesis. However, there is no consensus on the regulation of EGLN1 and its mechanism of action on nasopharyngeal carcinoma (NPC). This study explored the association of the expression of EGLN1 with characteristics of NPC tumors and its underlying mechanism. We found that the expression of EGLN1 showed a positive correlation with tumor T classification and clinical staging of patients with NPC. EGLN1 could promote cell proliferation, invasion and migration, and even enhance the cancer stem cells (CSCs) prosperity and radioresistance of NPC cells. Mechanistically, EGLN1 facilitated degradation of tumor protein p53 through the ubiquitination system. This effect could be weakened in the presence of dimethyloxalylglycine (DMOG), suggesting that EGLN1 down-regulated p53 based on its hydroxylase activity. In conclusion, overexpression of EGLN1 promoted oncogenesis and induced a CSC-like phenotype in NPC cells, then enhancing the ability for radioresistance by interacting with p53 in a hydroxylase-dependent manner. Thus, EGLN1 might serve as a potential therapeutic target for NPC.

A four-hypoxia-genes-based prognostic signature for oral squamous cell carcinoma

BACKGROUND

Oral squamous cell carcinoma (OSCC) is one of the most common maligancies of the head and neck. The prognosis was is significantly different among OSCC patients. This study aims to identify new biomarkers to establish a prognostic model to predict the survival of OSCC patients.

METHODS

The mRNA expression and corresponding clinical information of OSCC patients were downloaded from The Cancer Genome Atlas and Gene Expression Omnibus. Additionally, a total of 26 hypoxia-related genes were also obtained from a previous study. Univariate Cox regression analysis and LASSO Cox regression analysis were performed to screen the optimal hypoxia-related genes which were associated with the prognosis of OSCC. to establish the predictive model (Risk Score) was established for estimating the patient's overall survival (OS). Multivariate Cox regression analysis was used to determine whether the Risk Score was an independent prognostic factor. Based on all the independent prognostic factors, nomogram was established to predict the OS probability of OSCC patients. The relative proportion of 22 immune cell types in each patient was evaluated by CIBERSORT software.

RESULTS

We determined that a total of four hypoxia-related genes including ALDOA, P4HA1, PGK1 and VEGFA were significantly associated with the prognosis of OSCC patients. The nomogram established based on all the independent factors could reliably predict the long-term OS of OSCC patients. In addition, our resluts indicated that the inferior prognosis of OSCC patients with high Risk Score might be related to the immunosuppressive microenvironments.

CONCLUSION

This study shows that high expression of hypoxia-related genes including ALDOA, P4HA1, PGK1 and VEGFA is associated with poor prognosis in OSCC patients, and they can be used as potential markers for predicting prognosis in OSCC patients.

The non-canonical functions of HIF prolyl hydroxylases and their dual roles in cancer

The hypoxia-inducible factor (HIF) prolyl hydroxylases (PHDs) are dioxygenases using oxygen and 2-oxoglutarate as co-substrates. Under normoxia, PHDs hydroxylate the conserved prolyl residues of HIFα, leading to HIFα degradation. In hypoxia PHDs are inactivated, which results in HIFα accumulation. The accumulated HIFα enters nucleus and initiates gene transcription. Many studies have shown that PHDs have substrates other than HIFα, implying that they have HIF-independent non-canonical functions. Besides modulating protein stability, the PHDs-mediated prolyl hydroxylation affects protein-protein interaction and protein activity for alternative substrates. Increasing evidence indicates that PHDs also have hydroxylase-independent functions. They influence protein stability, enzyme activity, and protein-protein interaction in a hydroxylase-independent manner. These findings highlight the functional diversity and complexity of PHDs. Due to having inhibitory activity on HIFα, PHDs are proposed to act as tumor suppressors. However, research shows that PHDs exert either tumor-promoting or tumor-suppressing features. Here, we try to summarize the current understanding of PHDs hydroxylase-dependent and -independent functions and their roles in cancer.

Hypoxia-Driven Effects in Cancer: Characterization, Mechanisms, and Therapeutic Implications

Hypoxia, a common feature of solid tumors, greatly hinders the efficacy of conventional cancer treatments such as chemo-, radio-, and immunotherapy. The depletion of oxygen in proliferating and advanced tumors causes an array of genetic, transcriptional, and metabolic adaptations that promote survival, metastasis, and a clinically malignant phenotype. At the nexus of these interconnected pathways are hypoxia-inducible factors (HIFs) which orchestrate transcriptional responses under hypoxia. The following review summarizes current literature regarding effects of hypoxia on DNA repair, metastasis, epithelial-to-mesenchymal transition, the cancer stem cell phenotype, and therapy resistance. We also discuss mechanisms and pathways, such as HIF signaling, mitochondrial dynamics, exosomes, and the unfolded protein response, that contribute to hypoxia-induced phenotypic changes. Finally, novel therapeutics that target the hypoxic tumor microenvironment or interfere with hypoxia-induced pathways are reviewed.

Scutellarin resensitizes oxaliplatin-resistant colorectal cancer cells to oxaliplatin treatment through inhibition of PKM2

Although oxaliplatin is an effective chemotherapeutic drug commonly used for colorectal cancer (CRC) treatment, drug resistance usually occurs during the long-term use of it. It is urgent to create strategies to reduce the resistance of CRC cells to oxaliplatin. Oxaliplatin-resistant CRC cells (OR-SW480 and OR-HT29) were acquired through long-term exposure of CRC cells to oxaliplatin. It was found that OR-SW480 and OR-HT29 cells exhibited obvious lower sensitivity and a higher metabolism rate of glucose compared to their parental SW480 and HT29 cells, respectively. However, combination with scutellarin significantly resensitized the OR-SW480 and OR-HT29 cells to oxaliplatin-induced cytotoxicity. Mechanically, overexpression of pyruvate kinase isoenzyme M2 (PKM2) was responsible for the resistance to oxaliplatin in OR-SW480 and OR-HT29. Combination with scutellarin was able to inhibit the PKM2 activity and thus reduced the production of adenosine triphosphate (ATP) to sensitize the oxaliplatin-induced mitochondrial apoptosis pathway in both OR-SW480 and OR-HT29 cells. It was indicated that scutellarin resensitizes oxaliplatin-resistant CRC cells to oxaliplatin treatment through inhibition of PKM2.

Differential Effects of Trp53 Alterations in Murine Colorectal Cancer

BACKGROUND

Colorectal cancer (CRC) development is a multi-step process resulting in the accumulation of genetic alterations. Despite its high incidence, there are currently no mouse models that accurately recapitulate this process and mimic sporadic CRC. We aimed to develop and characterize a genetically engineered mouse model (GEMM) of Apc/Kras/Trp53 mutant CRC, the most frequent genetic subtype of CRC.

METHODS

Tumors were induced in mice with conditional mutations or knockouts in Apc, Kras, and Trp53 by a segmental adeno-cre viral infection, monitored via colonoscopy and characterized on multiple levels via immunohistochemistry and next-generation sequencing.

RESULTS

The model accurately recapitulates human colorectal carcinogenesis clinically, histologically and genetically. The Trp53 R172H hotspot mutation leads to significantly increased metastatic capacity. The effects of Trp53 alterations, as well as the response to treatment of this model, are similar to human CRC. Exome sequencing revealed spontaneous protein-modifying alterations in multiple CRC-related genes and oncogenic pathways, resulting in a genetic landscape resembling human CRC.

CONCLUSIONS

This model realistically mimics human CRC in many aspects, allows new insights into the role of TP53 in CRC, enables highly predictive preclinical studies and demonstrates the value of GEMMs in current translational cancer research and drug development.

The JPJDF has Synergistic Effect with Fluoropyrimidine in the Maintenance Therapy for Metastatic Colorectal Cancer

Background:

Maintenance chemotherapeutic regimen with low toxicity is needed for metastatic colorectal cancer. A recent patent has been issued on the spleen-strengthening and detoxification prescription (JPJDF), a traditional Chinese herbal medicinal formula with anti-angiogenesis effect. The clinical effect of JPJDF on the maintenance treatment of advanced colorectal cancer has not been evaluated.

Objective:

This study aims to evaluate the effectiveness and safety of JPJDF in combination with fluoropyrimidine compared to fluoropyrimidine alone as maintenance therapy for metastatic colorectal cancer.

Methods:

We applied a prospective, randomized, double-blinded, single center clinical study design. A total of 137 patients with advanced colorectal cancer were recruited. Patients received either Fluoropyrimidine (Flu-treated group, n = 68), or Fluoropyrimidine plus JPJDF (Flu-F-treated group, n = 69) as maintenance treatment after 6-cycle of FOLFOX4 or FOLFORI induction treatment. The primary endpoints were Progression-Free Survival (PFS) and Overall Survival (OS). The secondary endpoints were safety, Performance Status (PS) score and other symptoms.

Results:

The endpoint of disease progression was observed in 91.7% of patients. The PFS was 5.0 months and 3.0 months in the Flu-F-treated and Flu-treated groups, respectively. The OS was 15.0 months and 9.0 months in the Flu-F-treated and Flu-treated groups, respectively. Some common symptoms, such as hypodynamia, anepithymia, dizziness and tinnitus and shortness of breath, were improved in the Flu-F-treated group. There was no significant difference in the common adverse reactions between the two groups.

Conclusion:

JPJDF and fluoropyrimidine have synergistic effect in the maintenance treatment of mCRC.

5-Fluorouracil resistance mechanisms in colorectal cancer: From classical pathways to promising processes

Colorectal cancer (CRC) is a public health problem. It is the third most common cancer in the world, with nearly 1.8 million new cases diagnosed in 2018. The only curative treatment is surgery, especially for early tumor stages. When there is locoregional or distant invasion, chemotherapy can be introduced, in particular 5-fluorouracil (5-FU). However, the disease can become tolerant to these pharmaceutical treatments: resistance emerges, leading to early tumor recurrence. Different mechanisms can explain this 5-FU resistance. Some are disease-specific, whereas others, such as drug efflux, are evolutionarily conserved. These mechanisms are numerous and complex and can occur simultaneously in cells exposed to 5-FU. In this review, we construct a global outline of different mechanisms from disruption of 5-FU-metabolic enzymes and classic cellular processes (apoptosis, autophagy, glucose metabolism, oxidative stress, respiration, and cell cycle perturbation) to drug transporters and epithelial-mesenchymal transition induction. Particular interest is directed to tumor microenvironment function as well as epigenetic alterations and miRNA dysregulation, which are the more promising processes that will be the subject of much research in the future.

The diverse roles of SPOP in prostate cancer and kidney cancer

Multiple studies have confirmed that speckle-type pox virus and zinc finger (POZ) protein (SPOP) functions as a substrate adaptor of cullin 3-based E3 ligase and has a crucial role in various cellular processes via specific targeting of proteins for ubiquitination and subsequent proteasomal degradation. Dysregulation of SPOP-mediated proteolysis might be involved in the development and progression of human prostate and kidney cancers. In prostate cancer, SPOP seems to function as a tumour suppressor by targeting several proteins, including androgen receptor (AR), steroid receptor coactivator 3 (SRC3) and BRD4, for degradation, whereas it might function as an oncoprotein in kidney cancer, for example, by targeting phosphatase and tensin homologue (PTEN) for proteasomal degradation. In addition, nuclear SPOP targets AR for degradation and has a role as a tumour suppressor in prostate cancer; however, in kidney cancer, SPOP largely accumulates in the cytoplasm and fails to promote degradation of AR located in the nucleus, resulting in activation of AR-driven pathways and cancer progression. Owing to the context-dependent function of SPOP in human malignancies, further assessment of the molecular mechanisms involving SPOP in prostate and kidney cancers is needed to improve our understanding of its role in the development of these cancer types. Treatments that target SPOP might become therapeutic strategies in these malignancies in the future.

Understanding the Oxygen-Sensing Pathway and Its Therapeutic Implications in Diseases

Maintaining oxygen homeostasis is a most basic cellular process for adapting physiological oxygen variations, and its abnormality typically leads to various disorders in the human body. The key molecules of the oxygen-sensing system include the transcriptional regulator hypoxia-inducible factor (HIF), which controls a wide range of oxygen responsive target genes (eg, EPO and VEGF), certain members of the oxygen/2-oxoglutarate-dependent dioxygenase family, including the HIF proline hydroxylase (PHD, alias EGLN), and an E3 ubiquitin ligase component for HIF destruction called von Hippel-Lindau. In this review, we summarize the physiological role and highlight the pathologic function for each protein of the oxygen-sensing system. A better understanding of their molecular mechanisms of action will help uncover novel therapeutic targets and develop more effective treatment approaches for related human diseases, including cancer.

LYW-6, a novel cryptotanshinone derived STAT3 targeting inhibitor, suppresses colorectal cancer growth and metastasis

The constitutive activation of signal transducer and activator of transcription 3(STAT3) is associated with aggressive development and metastasis in colorectal cancer (CRC), but STAT3-targeting drugs remain elusive in clinic. Here, structure-based strategy was used to remodel the natural compound cryptotanshinone into a more effective STAT3 inhibitor LYW-6. Using the Biolayer Interferometry assay, we observed that LYW-6 exhibited specific interactions with STAT3(KD = 6.6 ± 0.7 μM). Western blot analysis and electrophoretic mobility shift assays (EMSA) showed that LYW-6 inhibited the phosphorylation of STAT3 tyrosine 705 (Tyr-705) and had slight effects on STAT1 and STAT5 phosphorylation. Western blot analysis on the upstream kinases of STAT3 confirmed that the inhibitory mechanism on p-STAT3 was independent of upstream kinases. Further investigation demonstrated that LYW-6 downregulated the expression of downstream oncogenes to inhibit cell viability, cell cycle development, and potently increased cell apoptosis in human CRC cells. The invasion and metastasis linked signaling was also blocked by LYW-6 treatment. LYW-6 was found to reduce the metastasis foci in lung on tail-lung metastasis models. In addition, it was observed that LYW-6 markedly diminished STAT3 phosphorylation in tumor tissue and significantly inhibited tumor growth on xenograft models. Tumor development on chemically-induced colorectal cancer model also significantly inhibited by LYW-6 treatment. These findings provided adequate evidence that STAT3 inhibitor LYW-6 might be a potential candidate agent for CRC treatment.

Prolyl hydroxylase 3 controls the intestine goblet cell generation through stabilizing ATOH1

Intestinal epithelia self-renew constantly and generate differentiated cells such as secretary goblet cells. The intestine goblet cells secrete gel-forming mucins that form mucus to create a barrier of defense. We reported previously that loss of prolyl hydroxylase (PHD) 3 led to disruption of the intestinal epithelial barrier function. However, the underlying mechanism remains elusive. Here, we demonstrate that PHD3 controls the generation of intestine goblet cell. We found that genetic ablation of Phd3 in mice intestine epithelial cells reduced the amount of goblet cells. Mechanistically, PHD3 bounds the E3 ubiquitin ligase HUWE1 and prevented HUWE1 from mediating ubiquitination and degradation of ATOH1, an essential driver for goblet cell differentiation. The prolyl hydroxylase activity-deficient variant PHD3(H196A) also prevented ATOH1 destruction. A genetic intestine epithelial PHD3(H196A)-knockin had no effect on ATOH1 expression or goblet cell amount in mice, suggesting that the PHD3 prolyl hydroxylase activity is dispensable for its ability to control ATOH1 expression and goblet cell generation. In dextran sulfate sodium (DSS)-induced experimental colitis, PHD3-knockout rather than PHD3(H196A)-knockin sensitized the mice to DSS treatment. Our results reveal an additional critical mechanism underlying the regulation of ATOH1 expression and goblet cell generation and highlight that PHD3 plays a role in controlling intestine goblet cell generation in a hydroxylase-independent manner.

PHD1 controls muscle mTORC1 in a hydroxylation-independent manner by stabilizing leucyl tRNA synthetase

mTORC1 is an important regulator of muscle mass but how it is modulated by oxygen and nutrients is not completely understood. We show that loss of the prolyl hydroxylase domain isoform 1 oxygen sensor in mice (PHD1^KO) reduces muscle mass. PHD1^KO muscles show impaired mTORC1 activation in response to leucine whereas mTORC1 activation by growth factors or eccentric contractions was preserved. The ability of PHD1 to promote mTORC1 activity is independent of its hydroxylation activity but is caused by decreased protein content of the leucyl tRNA synthetase (LRS) leucine sensor. Mechanistically, PHD1 interacts with and stabilizes LRS. This interaction is promoted during oxygen and amino acid depletion and protects LRS from degradation. Finally, elderly subjects have lower PHD1 levels and LRS activity in muscle from aged versus young human subjects. In conclusion, PHD1 ensures an optimal mTORC1 response to leucine after episodes of metabolic scarcity.

mTORC1 is an important regulator of muscle mass. Here, the authors show that the PHD1 controls muscle mass in a hydroxylation-independent manner. PHD1 prevents the degradation of leucine sensor LRS during oxygen and amino acid depletion to ensure effective mTORC1 activation in response to leucine.

Role of hypoxia in cancer therapy by regulating the tumor microenvironment

AIM

Clinical resistance is a complex phenomenon in major human cancers involving multifactorial mechanisms, and hypoxia is one of the key components that affect the cellular expression program and lead to therapy resistance. The present study aimed to summarize the role of hypoxia in cancer therapy by regulating the tumor microenvironment (TME) and to highlight the potential of hypoxia-targeted therapy.

METHODS

Relevant published studies were retrieved from PubMed, Web of Science, and Embase using keywords such as hypoxia, cancer therapy, resistance, TME, cancer, apoptosis, DNA damage, autophagy, p53, and other similar terms.

RESULTS

Recent studies have shown that hypoxia is associated with poor prognosis in patients by regulating the TME. It confers resistance to conventional therapies through a number of signaling pathways in apoptosis, autophagy, DNA damage, mitochondrial activity, p53, and drug efflux.

CONCLUSION

Hypoxia targeting might be relevant to overcome hypoxia-associated resistance in cancer treatment.

Epigenome Mapping Identifies Tumor-Specific Gene Expression in Primary Rectal Cancer

Epigenetic alterations play a central role in cancer development and progression. The acetylation of histone 3 at lysine 27 (H3K27ac) specifically marks active genes. While chromatin immunoprecipitation (ChIP) followed by next-generation sequencing (ChIP-seq) analyses are commonly performed in cell lines, only limited data are available from primary tumors. We therefore examined whether cancer-specific alterations in H3K27ac occupancy can be identified in primary rectal cancer. Tissue samples from primary rectal cancer and matched mucosa were obtained. ChIP-seq for H3K27ac was performed and differentially occupied regions were identified. The expression of selected genes displaying differential occupancy between tumor and mucosa were examined in gene expression data from an independent patient cohort. Differential expression of four proteins was further examined by immunohistochemistry. ChIP-seq for H3K27ac in primary rectal cancer and matched mucosa was successfully performed and revealed differential binding on 44 regions. This led to the identification of genes with increased H3K27ac, i.e., RIPK2, FOXQ1, KRT23, and EPHX4, which were also highly upregulated in primary rectal cancer in an independent dataset. The increased expression of these four proteins was confirmed by immunohistochemistry. This study demonstrates the feasibility of ChIP-seq-based epigenome mapping of primary rectal cancer and confirms the value of H3K27ac occupancy to predict gene expression differences.

Protein Hydroxylation by Hypoxia-Inducible Factor (HIF) Hydroxylases: Unique or Ubiquitous?

All metazoans that utilize molecular oxygen (O₂) for metabolic purposes have the capacity to adapt to hypoxia, the condition that arises when O₂ demand exceeds supply. This is mediated through activation of the hypoxia-inducible factor (HIF) pathway. At physiological oxygen levels (normoxia), HIF-prolyl hydroxylases (PHDs) hydroxylate proline residues on HIF-α subunits leading to their destabilization by promoting ubiquitination by the von-Hippel Lindau (VHL) ubiquitin ligase and subsequent proteasomal degradation. HIF-α transactivation is also repressed in an O₂-dependent way due to asparaginyl hydroxylation by the factor-inhibiting HIF (FIH). In hypoxia, the O₂-dependent hydroxylation of HIF-α subunits by PHDs and FIH is reduced, resulting in HIF-α accumulation, dimerization with HIF-β and migration into the nucleus to induce an adaptive transcriptional response. Although HIFs are the canonical substrates for PHD- and FIH-mediated protein hydroxylation, increasing evidence indicates that these hydroxylases may also have alternative targets. In addition to PHD-conferred alterations in protein stability, there is now evidence that hydroxylation can affect protein activity and protein/protein interactions for alternative substrates. PHDs can be pharmacologically inhibited by a new class of drugs termed prolyl hydroxylase inhibitors which have recently been approved for the treatment of anemia associated with chronic kidney disease. The identification of alternative targets of HIF hydroxylases is important in order to fully elucidate the pharmacology of hydroxylase inhibitors (PHI). Despite significant technical advances, screening, detection and verification of alternative functional targets for PHDs and FIH remain challenging. In this review, we discuss recently proposed non-HIF targets for PHDs and FIH and provide an overview of the techniques used to identify these.

Analysis of Differentially Expressed lncRNAs and mRNAs for the Identification of Hypoxia-Regulated Angiogenic Genes in Colorectal Cancer by RNA-Seq

Background

Hypoxia is an important feature of solid tumors and related to a perturbed blood supply in pathophysiologies. The aim of our research was to analyze the hypoxia response and elaborate its potential functions in colorectal cancer.

Material/Methods

The lncRNAs and mRNAs expression profile were analyzed in colorectal cancer cell line SW480 by RNA sequencing, and the functions and pathways of differentially expressed genes were screened by Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis.

Results

In this study, 77 lncRNAs and 1327 mRNAs were identified as differentially expressed. We discovered several novel lncRNAs, such as RP11-126K1.2, RP3-438O4.4, LINC01119, CTB-22K21.2, RP11-798M19.6, and RP11-2B6.3, which had not been previously reported in regulation by hypoxia. KEGG and GO analyses identified that the differentially expressed changes in mRNAs were mainly related to regulation of basic metabolic processes and gene transcription processes and were involved in several classical pathways which were linked to cancer.

Conclusions

Taken together, the present findings elucidate a set of differentially expressed lncRNAs and mRNAs involved in the hypoxia response process of colorectal cancer, which may serve as a candidate diagnostic biomarker and help to explain the mechanism of initial event in colorectal carcinogenesis in colorectal cancer.

p53 mediates hydroxyurea resistance in aneuploid cells of colon cancer

Aneuploidy refers to aberrancies in cellular chromosome count, which is prevalent in most human cancers. Chemotherapy is an effective cancer treatment; however, the development of drug resistance is a major concern of conventional chemotherapy. The chemotherapy agent hydroxyurea (HU) targets proliferating cells and has long been applied to treat various human cancers. It remains elusive whether aneuploidy affects the drug sensitivity of hydroxyurea. By generating an inducible aneuploidy model, we found that aneuploid colon cancer cells were resistant to HU treatment compared to euploid controls. Surprisingly, further analyses showed that the HU resistance was dependent on the expression of wild type p53. Activation of the p53 pathway in aneuploidy cells reduced cell proliferation but generated resistance of tumor cells to HU treatment. HU resistance was abrogated in aneuploid cells if p53 was absent but re-gained when inducing proliferation repression in cells by serum deprivation. Our results demonstrate that the HU resistance developed in aneuploid colon cancer cells is mediated by wild type p53 and indicates the prognostic value of combining karyotypic and p53 status in clinical cancer treatment.

Inflammation and Hypoxia: HIF and PHD Isoform Selectivity

Cells sense and respond to hypoxia through the activity of the transcription factor HIF (hypoxia-inducible factor) and its regulatory hydroxylases, the prolyl hydroxylase domain enzymes (PHDs). Multiple isoforms of HIFs and PHDs exist, and isoform-selective roles have been identified in the context of the inflammatory environment, which is itself frequently hypoxic. Recent advances in the field have highlighted the complexity of this system, particularly with regards to the cell and context-specific activity of HIFs and PHDs. Because novel therapeutic agents which regulate this pathway are nearing the clinic, understanding the role of HIFs and PHDs in inflammation outcomes is an essential step in avoiding off-target effects and, crucially, in developing new anti-inflammatory strategies.

PHD3 Regulates p53 Protein Stability by Hydroxylating Proline 359

Cellular p53 protein levels are regulated by a ubiquitination/de-ubiquitination cycle that can target the protein for proteasomal destruction. The ubiquitination reaction is catalyzed by a multitude of ligases, whereas the removal of ubiquitin chains is mediated by two deubiquitinating enzymes (DUBs), USP7 (HAUSP) and USP10. Here, we show that PHD3 hydroxylates p53 at proline 359, a residue that is in the p53-DUB binding domain. Hydroxylation of p53 upon proline 359 regulates its interaction with USP7 and USP10, and its inhibition decreases the association of p53 with USP7/USP10, increases p53 ubiquitination, and rapidly reduces p53 protein levels independently of mRNA expression. Our results show that p53 is a PHD3 substrate and that hydroxylation by PHD3 regulates p53 protein stability through modulation of ubiquitination.

Hypoxic Signalling in Tumour Stroma

Hypoxia is a common feature in solid tumors and is associated with cancer progression. The main regulators of the hypoxic response are hypoxia-inducible transcription factors (HIFs) that guide the cellular adaptation to hypoxia by gene activation. The actual oxygen sensing is performed by HIF prolyl hydroxylases (PHDs) that under normoxic conditions mark the HIF-α subunit for degradation. Cancer progression is not regulated only by the cancer cells themselves but also by the whole tumor microenvironment, which consists of cellular and extracellular components. Hypoxic conditions also affect the stromal compartment, where stromal cells are in close contact with the cancer cells. The important function of HIF in cancer cells has been shown by many animal models and described in hundreds of reviews, but less in known about PHDs and even less PHDs in stromal cells. Here, we review hypoxic signaling in tumors, mainly in the tumor stroma, with a focus on HIFs and PHDs.

Metabolic Reprogramming and Redox Signaling in Pulmonary Hypertension

Pulmonary hypertension is a complex disease of the pulmonary vasculature, which in severe cases terminates in right heart failure. Complex remodeling of pulmonary arteries comprises the central issue of its pathology. This includes extensive proliferation, apoptotic resistance and inflammation. As such, the molecular and cellular features of pulmonary hypertension resemble hallmark characteristics of cancer cell behavior. The vascular remodeling derives from significant metabolic changes in resident cells, which we describe in detail. It affects not only cells of pulmonary artery wall, but also its immediate microenvironment involving cells of immune system (i.e., macrophages). Thus aberrant metabolism constitutes principle component of the cancer-like theory of pulmonary hypertension. The metabolic changes in pulmonary artery cells resemble the cancer associated Warburg effect, involving incomplete glucose oxidation through aerobic glycolysis with depressed mitochondrial catabolism enabling the fueling of anabolic reactions with amino acids, nucleotides and lipids to sustain proliferation. Macrophages also undergo overlapping but distinct metabolic reprogramming inducing specific activation or polarization states that enable their participation in the vascular remodeling process. Such metabolic synergy drives chronic inflammation further contributing to remodeling. Enhanced glycolytic flux together with suppressed mitochondrial bioenergetics promotes the accumulation of reducing equivalents, NAD(P)H. We discuss the enzymes and reactions involved. The reducing equivalents modulate the regulation of proteins using NAD(P)H as the transcriptional co-repressor C-terminal binding protein 1 cofactor and significantly impact redox status (through GSH, NAD(P)H oxidases, etc.), which together act to control the phenotype of the cells of pulmonary arteries. The altered mitochondrial metabolism changes its redox poise, which together with enhanced NAD(P)H oxidase activity and reduced enzymatic antioxidant activity promotes a pro-oxidative cellular status. Herein we discuss all described metabolic changes along with resultant alterations in redox status, which result in excessive proliferation, apoptotic resistance, and inflammation, further leading to pulmonary arterial wall remodeling and thus establishing pulmonary artery hypertension pathology.

Upregulation of let-7f-5p promotes chemotherapeutic resistance in colorectal cancer by directly repressing several pro-apoptotic proteins

Colorectal cancer (CRC) is one of the most frequently occurring primary malignant tumors worldwide. Chemotherapeutic resistance is a major clinical problem in the treatment of CRC. Therefore, it is of great importance to investigate novel biomarkers that may predict chemoresistance and facilitate the development of individualized treatment for patients with CRC. The present study reported that let-7f-5p expression was elevated in chemotherapy-resistant CRC tissues compared with chemotherapy-sensitive tissues. Furthermore, upregulating let-7f-5p increased the expression levels of the anti-apoptotic proteins, B-cell lymphoma 2 (Bcl-2) and B-cell lymphoma-extra large (Bcl-xL), and decreased the activity of caspase-3 and caspase-9 in CRC cells. By contrast, downregulating let-7f-5p yielded the opposite effect. Notably, the results indicated that let-7f-5p promoted chemotherapeutic resistance by directly repressing the expression of several pro-apoptotic proteins, including tumor protein p53, tumor protein p53-inducible nuclear protein 1, tumor protein p53-inducible nuclear protein 2 and caspase-3. Therefore, a novel mechanism by which let-7f-5p enhances the resistance of CRC cells to chemotherapeutics has been revealed, indicating that silencing let-7f-5p may become an effective therapeutic strategy against CRC.

The PHD1 oxygen sensor in health and disease

The hypoxia-inducible factor (HIF) co-ordinates the adaptive transcriptional response to hypoxia in metazoan cells. The hypoxic sensitivity of HIF is conferred by a family of oxygen-sensing enzymes termed HIF hydroxylases. This family consists of three prolyl hydroxylases (PHD1-3) and a single asparagine hydroxylase termed factor inhibiting HIF (FIH). It has recently become clear that HIF hydroxylases are functionally non-redundant and have discrete but overlapping physiological roles. Furthermore, altered abundance or activity of these enzymes is associated with a number of pathologies. Pharmacological HIF-hydroxylase inhibitors have recently proven to be both tolerated and therapeutically effective in patients. In this review, we focus on the physiology, pathophysiology and therapeutic potential of the PHD1 isoform, which has recently been implicated in diseases including inflammatory bowel disease, ischaemia and cancer.

A Network Pharmacology Approach to Uncover the Multiple Mechanisms of Hedyotis diffusa Willd. on Colorectal Cancer

Background

As one of the most frequently diagnosed cancer diseases globally, colorectal cancer (CRC) remains an important cause of cancer-related death. Although the traditional Chinese herb Hedyotis diffusa Willd. (HDW) has been proven to be effective for treating CRC in clinical practice, its definite mechanisms have not been completely deciphered.

Objective

The aim of our research is to systematically explore the multiple mechanisms of HDW on CRC.

Methods

This study adopted the network pharmacology approach, which was mainly composed of active component gathering, target prediction, CRC gene collection, network analysis, and gene enrichment analysis.

Results

The network analysis showed that 10 targets might be the therapeutic targets of HDW on CRC, namely, HRAS, PIK3CA, KRAS, TP53, APC, BRAF, GSK3B, CDK2, AKT1, and RAF1. The gene enrichment analysis implied that HDW probably benefits patients with CRC by modulating pathways related to cancers, infectious diseases, endocrine system, immune system, nervous system, signal transduction, cellular community, and cell motility.

Conclusions

This study partially verified and predicted the pharmacological and molecular mechanism of HDW against CRC from a holistic perspective, which will also lay a foundation for the further experimental research and clinical rational application of HDW.

Hallmarks of Pulmonary Hypertension: Mesenchymal and Inflammatory Cell Metabolic Reprogramming

SIGNIFICANCE

The molecular events that promote the development of pulmonary hypertension (PH) are complex and incompletely understood. The complex interplay between the pulmonary vasculature and its immediate microenvironment involving cells of immune system (i.e., macrophages) promotes a persistent inflammatory state, pathological angiogenesis, and fibrosis that are driven by metabolic reprogramming of mesenchymal and immune cells. Recent Advancements: Consistent with previous findings in the field of cancer metabolism, increased glycolytic rates, incomplete glucose and glutamine oxidation to support anabolism and anaplerosis, altered lipid synthesis/oxidation ratios, increased one-carbon metabolism, and activation of the pentose phosphate pathway to support nucleoside synthesis are but some of the key metabolic signatures of vascular cells in PH. In addition, metabolic reprogramming of macrophages is observed in PH and is characterized by distinct features, such as the induction of specific activation or polarization states that enable their participation in the vascular remodeling process.

CRITICAL ISSUES

Accumulation of reducing equivalents, such as NAD(P)H in PH cells, also contributes to their altered phenotype both directly and indirectly by regulating the activity of the transcriptional co-repressor C-terminal-binding protein 1 to control the proliferative/inflammatory gene expression in resident and immune cells. Further, similar to the role of anomalous metabolism in mitochondria in cancer, in PH short-term hypoxia-dependent and long-term hypoxia-independent alterations of mitochondrial activity, in the absence of genetic mutation of key mitochondrial enzymes, have been observed and explored as potential therapeutic targets.

FUTURE DIRECTIONS

For the foreseeable future, short- and long-term metabolic reprogramming will become a candidate druggable target in the treatment of PH. Antioxid. Redox Signal. 28, 230-250.

PHD3 Controls Lung Cancer Metastasis and Resistance to EGFR Inhibitors through TGFα

Lung cancer is the leading cause of cancer-related death worldwide, in large part due to its high propensity to metastasize and to develop therapy resistance. Adaptive responses to hypoxia and epithelial-mesenchymal transition (EMT) are linked to tumor metastasis and drug resistance, but little is known about how oxygen sensing and EMT intersect to control these hallmarks of cancer. Here, we show that the oxygen sensor PHD3 links hypoxic signaling and EMT regulation in the lung tumor microenvironment. PHD3 was repressed by signals that induce EMT and acted as a negative regulator of EMT, metastasis, and therapeutic resistance. PHD3 depletion in tumors, which can be caused by the EMT inducer TGFβ or by promoter methylation, enhanced EMT and spontaneous metastasis via HIF-dependent upregulation of the EGFR ligand TGFα. In turn, TGFα stimulated EGFR, which potentiated SMAD signaling, reinforcing EMT and metastasis. In clinical specimens of lung cancer, reduced PHD3 expression was linked to poor prognosis and to therapeutic resistance against EGFR inhibitors such as erlotinib. Reexpression of PHD3 in lung cancer cells suppressed EMT and metastasis and restored sensitivity to erlotinib. Taken together, our results establish a key function for PHD3 in metastasis and drug resistance and suggest opportunities to improve patient treatment by interfering with the feedforward signaling mechanisms activated by PHD3 silencing.Significance: This study links the oxygen sensor PHD3 to metastasis and drug resistance in cancer, with implications for therapeutic improvement by targeting this system. Cancer Res; 78(7); 1805-19. ©2018 AACR.

Hypoxia-inducible factor prolyl-4-hydroxylase-1 is a convergent point in the reciprocal negative regulation of NF-κB and p53 signaling pathways

Hypoxia-inducible factor 1α (HIF1α) induces the expression of several hundred genes in hypoxia aiming at restoration of oxygen homeostasis. HIF prolyl-4-hydroxylases (HIF-P4Hs) regulate the stability of HIF1α in an oxygen-dependent manner. Hypoxia is a common feature in inflammation and cancer and the HIF pathway is closely linked with the inflammatory NF-κB and tumor suppressor p53 pathways. Here we show that genetic inactivation or chemical inhibition of HIF-P4H-1 leads to downregulation of proinflammatory genes, while proapoptotic genes are upregulated. HIF-P4H-1 inactivation reduces the inflammatory response under LPS stimulus in vitro and in an acute skin inflammation model in vivo. Furthermore, HIF-P4H-1 inactivation increases p53 activity and stability and hydroxylation of proline 142 in p53 has an important role in this regulation. Altogether, our data suggest that HIF-P4H-1 inhibition may be a promising therapeutic candidate for inflammatory diseases and cancer, enhancing the reciprocal negative regulation of the NF-κB and p53 pathways.

Regulatory players of DNA damage repair mechanisms: Role in Cancer Chemoresistance

DNA damaging agents are most common in chemotherapeutic molecules that act against cancer. However, cancer cells possess inherent biological features to overcome DNA damages by activating various distinct repair mechanisms and pathways. Importantly, various oncogenes, cancer stem cells (CSCs), hypoxic environment, transcription factors and bystander signaling that are activated in the cancer cells influence DNA repair, thereby effectively repairing the DNA damage. Repaired cancer cells often become more resistance to further therapy and results in disease recurrence. In this review, we summarize how the various signaling pathways in cancer cells regulates DNA repair and induce chemoresistance.

Ginsenoside 20(S)-Rg3 suppresses ovarian cancer migration via hypoxia-inducible factor 1 alpha and nuclear factor-kappa B signals

Hypoxia-inducible factor 1 is believed to play a prominent role in the survival and developing progress of cancers. As a result, inhibiting α subunit of hypoxia-inducible factor 1 represents an attractive strategy against tumor. Although hypoxia-inducible factor 1α is a hypoxia-regulated subunit, increasing evidence indicates that hypoxia-inducible factor 1α could stable expression under normoxic conditions, regulated by non-hypoxia-mediated mechanisms. However, there are few strategies to target hypoxia-inducible factor 1α under normoxic conditions. Here, we report that ginsenoside 20(S)-Rg3, one of the main active ingredients in red ginseng, restrains hypoxia-inducible factor 1α expression under normal oxygen levels in human ovarian cancer cell lines, SKOV3 and 3AO, which leads to potently inhibits migration of ovarian cancer in vitro and in vivo. 20(S)-Rg3 could decrease the expression of hypoxia-inducible factor 1α by upregulation of prolyl hydroxylase domain protein 1 to promoting hypoxia-inducible factor 1α ubiquitin-proteasome degradation under normal oxygen levels. Furthermore, 20(S)-Rg3 could attenuate the expression of nuclear factor-κ B, which may be another possible mechanism for 20(S)-Rg3 to block ovarian cancer migration. Taken together, our study suggests that 20(S)-Rg3 is a strong inhibitor of hypoxia-inducible factor 1α, which may provide a novel agent for future treatments for ovarian cancer.

Hypoxia and Inflammation in Cancer, Focus on HIF and NF-κB

Cancer is often characterised by the presence of hypoxia and inflammation. Paramount to the mechanisms controlling cellular responses under such stress stimuli, are the transcription factor families of Hypoxia Inducible Factor (HIF) and Nuclear Factor of κ-light-chain-enhancer of activated B cells (NF-κB). Although, a detailed understating of how these transcription factors respond to their cognate stimulus is well established, it is now appreciated that HIF and NF-κB undergo extensive crosstalk, in particular in pathological situations such as cancer. Here, we focus on the current knowledge on how HIF is activated by inflammation and how NF-κB is modulated by hypoxia. We summarise the evidence for the possible mechanism behind this activation and how HIF and NF-κB function impacts cancer, focusing on colorectal, breast and lung cancer. We discuss possible new points of therapeutic intervention aiming to harness the current understanding of the HIF-NF-κB crosstalk.

Tumor suppressor SPOP ubiquitinates and degrades EglN2 to compromise growth of prostate cancer cells

EglN prolyl hydroxylases, a family of oxygen-sensing enzymes, hydroxylate distinct proteins to modulate diverse physiopathological signals. Aberrant regulations of EglNs result in multiple human diseases, including cancer. Different from EglN1 which function largely depends on the role of hypoxia-induce factor alpha (HIFα) in tumors, the functional significance and the upstream regulatory mechanisms of EglN2, especially in prostate cancer setting, remain largely unclear. Here, we demonstrated that dysregulation of EglN2 facilitated prostate cancer growth both in cells and in vivo. Notably, EglN2 was identified highly expressed in human prostate cancer tissues. Mechanically, Cullin 3-based E3 ubiquitin ligase SPOP, a well-characterized tumor suppressor in prostate cancer, could recognize and destruct EglN2. Meanwhile, androgen receptor (AR), playing a pivotal role in progression and development of prostate cancer, could transcriptionally up-regulate EglN2. Pathologically, SPOP loss-of-function mutations or AR amplification, frequently occurring in prostate cancers, could significantly accumulate EglN2 abundance. Therefore, our study not only underlines an oncogenic role of EglN2 in prostate cancer, but also highlights SPOP as a tumor suppressor to down-regulate EglN2 in prostate cancer.

New Insights into Protein Hydroxylation and Its Important Role in Human Diseases

Protein hydroxylation is a post-translational modification catalyzed by 2-oxoglutarate-dependent dioxygenases. The hydroxylation modification can take place on various amino acids, including but not limited to proline, lysine, asparagine, aspartate and histidine. A classical example of this modification is hypoxia inducible factor alpha (HIF-α) prolyl hydroxylation, which affects HIF-α protein stability via the Von-Hippel Lindau (VHL) tumor suppressor pathway, a Cullin 2-based E3 ligase adaptor protein frequently mutated in kidney cancer. In addition to protein stability regulation, protein hydroxylation may influence other post-translational modifications or the kinase activity of the modified protein (such as Akt and DYRK1A/B). In other cases, protein hydroxylation may alter protein-protein interaction and its downstream signaling events in vivo (such as OTUB1, MAPK6 and eEF2K). In this review, we highlight the recently identified protein hydroxylation targets and their pathophysiological roles, especially in cancer settings. Better understanding of protein hydroxylation will help identify novel therapeutic targets and their regulation mechanisms to foster development of more effective treatment strategies for various human cancers.

Elevated HMGA2 expression is associated with cancer aggressiveness and predicts poor outcome in breast cancer

High mobility group AT-hook 2 (HMGA2) is involved in a wide spectrum of biological processes and is upregulated in several tumors. Here, we collected 273 breast cancer (BC) specimens as a training set and 310 specimens as a validation set to examine the expression of HMGA2 by immunohistochemical staining. It was found that HMGA2 expression was significantly positively correlated with advanced tumor grade and poor survival. Subgroup analysis indicated that high level of HMGA2 was significantly correlated with poor prognosis, especially in the subgroups of stage II-III, low pathological grade and non-triple negative breast cancer cases. Gene set enrichment analysis (GSEA) demonstrated a significant positive correlation between HMGA2 level and the gene expression signature of metaplastic and mesenchymal phenotype. Importantly, we also observed that ectopic expression of HMGA2 promoted the migration and invasion of breast cancer cells, and protected cancer cells against genotoxic stress from agents stimulating P53 (Ser15) phosphorylation. As a conclusion, expression of HMGA2 might indicate more advanced malignancy of breast cancer. Thus we believe HMGA2 could serve as a biomarker of poor prognosis and a novel target in treating BC tumors.