The mechanism of DAB2IP in chemoresistance of prostate cancer cells

An update on the tumor-suppressive functions of the RasGAP protein DAB2IP with focus on therapeutic implications

The dynamic crosstalk between tumor and stromal cells is a major determinant of cancer aggressiveness. The tumor-suppressor DAB2IP (Disabled homolog 2 interacting protein) plays an important role in this context, since it modulates cell responses to multiple extracellular inputs, including inflammatory cytokines and growth factors. DAB2IP is a RasGAP and negatively controls Ras-dependent mitogenic signals. In addition, it modulates other major oncogenic pathways, including TNFα/NF-κB, WNT/β-catenin, PI3K/AKT, and androgen receptor signaling. In line with its tumor-suppressive role, DAB2IP is frequently inactivated in cancer by transcriptional and post-transcriptional mechanisms, including promoter methylation, microRNA-mediated downregulation, and protein-protein interactions. Intriguingly, some observations suggest that downregulation of DAB2IP in cells of the tumor stroma could foster establishment of a pro-metastatic microenvironment. This review summarizes recent insights into the tumor-suppressive functions of DAB2IP and the consequences of its inactivation in cancer. In particular, we explore potential approaches aimed at reactivating DAB2IP, or augmenting its expression levels, as a novel strategy in cancer treatment. We suggest that reactivation or upregulation of DAB2IP would concurrently attenuate multiple oncogenic pathways in both cancer cells and the tumor microenvironment, with implications for improved treatment of a broad spectrum of tumors.

DAB2IP inhibits glucose uptake by modulating HIF-1α ubiquitination under hypoxia in breast cancer

Metabolic reprogramming has become increasingly important in tumor biology research. The glucose metabolic pathway is a major energy source and is often dysregulated in breast cancer. DAB2IP is widely reported to be a tumor suppressor that acts as a scaffold protein to suppress tumor malignancy in breast cancer. Interestingly, DAB2IP has also been found to be a potential regulator of glucose uptake; however, the exact mechanism remains unclear. In this study, we found that DAB2IP inhibited glucose uptake under hypoxia conditions in breast cancer cells by suppressing HIF-1α signals. Mechanically, DAB2IP interacted with the E3 ubiquitin ligase STUB1 via its PER domain, thus triggering STUB1 mediated HIF-1α ubiquitylation and degradation, and inhibit glucose metabolism and tumor progression. Deleting the PER domain abrogated the DAB2IP-related inhibitory effects on glucose uptake, intracellular ATP production, and lactic acid production in breast cancer cells. These findings elucidate the biological roles of DAB2IP in cancer-related glucose metabolism as well as a novel mechanism by which STUB1-driven HIF-1α ubiquitylated degradation is regulated in breast cancer.

The scaffold protein disabled 2 (DAB2) and its role in tumor development and progression

BACKGROUND

Disabled 2 (DAB2) is a multifunctional protein that has emerged as a critical component in the regulation of tumor growth. Its dysregulation is implicated in various types of cancer, underscoring its importance in understanding the molecular mechanisms underlying tumor development and progression. This review aims to unravel the intricate molecular mechanisms by which DAB2 exerts its tumor-suppressive functions within cancer signaling pathways.

METHODS AND RESULTS

We conducted a comprehensive review of the literature focusing on the structure, expression, physiological functions, and tumor-suppressive roles of DAB2. We provide an overview of the structure, expression, and physiological functions of DAB2. Evidence supporting DAB2's role as a tumor suppressor is explored, highlighting its ability to inhibit cell proliferation, induce apoptosis, and modulate key signaling pathways involved in tumor suppression. The interaction between DAB2 and key oncogenes is examined, elucidating the interplay between DAB2 and oncogenic signaling pathways. We discuss the molecular mechanisms underlying DAB2-mediated tumor suppression, including its involvement in DNA damage response and repair, regulation of cell cycle progression and senescence, and modulation of epithelial-mesenchymal transition (EMT). The review explores the regulatory networks involving DAB2, covering post-translational modifications, interactions with other tumor suppressors, and integration within complex signaling networks. We also highlight the prognostic significance of DAB2 and its role in pre-clinical studies of tumor suppression.

CONCLUSION

This review provides a comprehensive understanding of the molecular mechanisms by which DAB2 exerts its tumor-suppressive functions. It emphasizes the significance of DAB2 in cancer signaling pathways and its potential as a target for future therapeutic interventions.

Disable 2, A Versatile Tissue Matrix Multifunctional Scaffold Protein with Multifaceted Signaling: Unveiling Role in Breast Cancer for Therapeutic Revolution

The Disabled-2 (DAB2) protein, found in 80-90% of various tumors, including breast cancer, has been identified as a potential tumor suppressor protein. On the contrary, some hypothesis suggests that DAB2 is associated with the modulation of the Ras/MAPK pathway by endocytosing the Grb/Sos1 signaling complex, which produces oncogenes and chemoresistance to anticancer drugs, leading to increased tumor growth and metastasis. DAB2 has multiple functions in several disorders and is typically under-regulated in several cancers, making it a potential target for treatment of cancer therapy. The primary function of DAB2 is the modulation of transforming growth factor- β (TGF-β) mediated endocytosis, which is involved in several mechanisms of cancer development, including tumor suppression through promoting apoptosis and suppressing cell proliferation. In this review, we will discuss in detail the mechanisms through which DAB2 leads to breast cancer and various advancements in employing DAB2 in the treatment of breast cancer. Additionally, we outlined its role in other diseases. We propose that upregulating DAB2 could be a novel approach to the therapeutics of breast cancer.

Disabled-2, a versatile tissue matrix multifunctional scaffold protein with multifaceted signaling: Unveiling its potential in the cancer battle

A multifunctional scaffold protein termed Disabled-2 (Dab2) has recently gained attention in the scientific community and has emerged as a promising candidate in the realm of cancer research. Dab2 protein is involved in a variety of signaling pathways, due to which its significance in the pathogenesis of several carcinomas has drawn considerable attention. Dab2 is essential for controlling the advancement of cancer because it engages in essential signaling pathways such as the Wnt/β-catenin, epidermal growth factor receptor (EGFR), and transforming growth factor-beta (TGF-β) pathways. Dab2 can also repress epithelial-mesenchymal transition (EMT) which is involved in tumor progression with metastatic expansion and adds another layer of significance to its possible impact on cancer spread. Furthermore, the role of Dab2 in processes such as cell growth, differentiation, apoptosis, invasion, and metastasis has been explored in certain investigative studies suggesting its significance. The present review examines the role of Dab2 in the pathogenesis of various cancer subtypes including breast cancer, ovarian cancer, gastric cancer, prostate cancer, and bladder urothelial carcinoma and also sheds some light on its potential to act as a therapeutic target and a prognostic marker in the treatment of various carcinomas. By deciphering this protein's diverse signaling, we hope to provide useful insights that may pave the way for novel therapeutic techniques and tailored treatment approaches in cancer management. Preclinical and clinical trial data on the impact of Dab2 regulation in cancer have also been included, allowing us to delineate role of Dab2 in tumor suppressor function, as well as its correlation with disease stage classification and potential therapy options. However, we observed that there is very scarce data in the form of studies on the evaluation of Dab2 role and treatment function in carcinomas, and further research into this matter could prove beneficial in the generation of novel therapeutic agents for patient-centric and tailored therapy, as well as early prognosis of carcinomas.

Wnt Signaling and Therapeutic Resistance in Castration-Resistant Prostate Cancer

Purpose of Review

Castration-resistant prostate cancer (CRPC) is a lethal form of prostate cancer (PCa) due to the development of resistance to androgen deprivation therapy and anti-androgens. Here, we review the emerging role of Wnt signaling in therapeutic resistance of CRPC.

Recent Findings

Convincing evidence have accumulated that Wnt signaling is aberrantly activated through genomic alterations and autocrine and paracrine augmentations. Wnt signaling plays a critical role in a subset of CRPC and in resistance to anti-androgen therapies. Wnt signaling navigates CRPC through PCa heterogeneity, neuroendocrine differentiation, DNA repair, PCa stem cell maintenance, epithelial-mesenchymal-transition and metastasis, and immune evasion.

Summary

Components of Wnt signaling can be harnessed for inhibiting PCa growth and metastasis and for developing novel therapeutic strategies to manage metastatic CRPC. There are many Wnt pathway-based potential drugs in different stages of pre-clinical development and clinical trials but so far, no Wnt signaling-specific drug has been approved by FDA for clinical use in CRPC.

Molecular Insight into Prostate Cancer: Preventive Role of Selective Bioactive Molecules

Prostate cancer (CaP) is one of the most prevalent male malignancies, accounting for a considerable number of annual mortalities. However, the prompt identification of early-stage CaP often faces delays due to diverse factors, including socioeconomic inequalities. The androgen receptor (AR), in conjunction with various other signaling pathways, exerts a central influence on the genesis, progression, and metastasis of CaP, with androgen deprivation therapy (ADT) serving as the primary therapeutic strategy. Therapeutic modalities encompassing surgery, chemotherapy, hormonal intervention, and radiotherapy have been formulated for addressing early and metastatic CaP. Nonetheless, the heterogeneous tumor microenvironment frequently triggers the activation of signaling pathways, culminating in the emergence of chemoresistance, an aspect to which cancer stem cells (CSCs) notably contribute. Phytochemicals emerge as reservoirs of bioactive agents conferring manifold advantages against human morbidity. Several of these phytochemicals demonstrate potential chemoprotective and chemosensitizing properties against CaP, with selectivity exhibited towards malignant cells while sparing their normal counterparts. In this context, the present review aims to elucidate the intricate molecular underpinnings associated with metastatic CaP development and the acquisition of chemoresistance. Moreover, the contributions of phytochemicals to ameliorating CaP initiation, progression, and chemoresistance are also discussed.

The role and function of CLU in cancer biology and therapy

Clusterin (CLU) is a highly evolutionary conserved glycoprotein with multiple isoform-specific functions and is widely distributed in different species. Accumulated evidence has shown the prominent role of CLU in regulating several essential physiological processes, including programmed cell death, metastasis, invasion, proliferation and cell growth via regulating diverse signaling pathways to mediate cancer progression in various cancers, such as prostate, breast, lung, liver, colon, bladder and pancreatic cancer. Several studies have revealed the potential benefit of inhibiting CLU in CLU inhibition-based targeted cancer therapies in vitro, in vivo or in human, suggesting CLU is a promising therapeutic target. This review discusses the multiple functions and mechanisms of CLU in regulating tumor progression of various cancers and summarizes the inhibitors of CLU used in CLU inhibition-based targeted cancer therapies.

Hypoxia-driven miR-1307-3p promotes hepatocellular carcinoma cell proliferation and invasion by modulating DAB2 interacting protein

Hypoxia is a common feature of the solid tumor microenvironment that is presented as poor clinical outcomes in multiple tumor types, including HCC. Hypoxia stabilizes HIF-1α/HIF-2α, which then moves into the nucleus and binds with HIF-1β to form a transcription complex, thereby promoting the transcription of target genes, including mRNAs, miRNAs and lncRNAs to exert their biological functions. Here, through a series of functional assay, including hypoxia culture, MTT, colony-formation, Transwell, qRT-PCR and western blot, we confirmed that miR-1307-3p, as a novel hypoxia-responsive factor, can be directly transcribed by HIF-1α rather than HIF-2α. Hypoxia-driven miR-1307-3p facilitated proliferation and invasion of HCC cells via repressing DAB2IP. Moreover, under hypoxia microenvironment, DAB2IP, as a direct target of miR-1307-3p, was down-regulated to activate AKT/mTOR signaling to further maintain the expression level of HIF-1α, thereby forming a feedback loop between HIF-1α/miR-1307-3p and DAB2IP. Targeting miR-1307-3p/DAB2IP axis also modulated tumor growth and metastasis in vivo. In summary, there exists a feedback loop between HIF-1α/miR-1307-3p and DAB2IP in HCC. Targeting a vicious feedback loop between HIF-1α/miR-1307-3p and DAB2IP may be a promising strategy to combat HCC.

DAB2IP regulates intratumoral testosterone synthesis and CRPC tumor growth by ETS1/AKR1C3 signaling

The intratumoral androgen synthesis is one of the mechanisms by which androgen receptor (AR) is aberrantly re-activated in castration-resistant prostate cancer (CRPC) after androgen ablation. However, pathways controlling steroidogenic enzyme expression and de novo androgen synthesis in prostate cancer (PCa) cells are largely unknown. In this study, we explored the potential roles of DAB2IP in testosterone synthesis and CRPC tumor growth. Indeed, DAB2IP loss could maintain AR transcriptional activity, PSA re-expression and tumor growth under castrated condition in vitro and in vivo, and reprogram the expression profiles of steroidogenic enzymes, including AKR1C3. Mechanistically, DAB2IP could dramatically inhibit the AKR1C3 promoter activity and the conversion from androgen precursors (i.e., DHEA) to testosterone through PI3K/AKT/mTOR/ETS1 signaling. Consistently, there was a high co-expression of ETS1 and AKR1C3 in PCa tissues and xenografts, and their expression in prostate tissues could also restore AR nuclear staining in castrated DAB2IP-/- mice after DHEA supplement. Together, this study reveals a novel regulation of intratumoral de novo androgen synthesis in CRPC, and provides the DAB2IP/ETS1/AKR1C3 signaling as a potential therapeutic target.

Mitotic phosphorylation of tumor suppressor DAB2IP maintains spindle assembly checkpoint and chromosomal stability through activating PLK1-Mps1 signal pathway and stabilizing mitotic checkpoint complex

Chromosomal instability (CIN) is a driving force for cancer development. The most common causes of CIN include the dysregulation of the spindle assembly checkpoint (SAC), which is a surveillance mechanism that prevents premature chromosome separation during mitosis by targeting anaphase-promoting complex/cyclosome (APC/C). DAB2IP is frequently silenced in advanced prostate cancer (PCa) and is associated with aggressive phenotypes of PCa. Our previous study showed that DAB2IP activates PLK1 and functions in mitotic regulation. Here, we report the novel mitotic phosphorylation of DAB2IP by Cdks, which mediates DAB2IP's interaction with PLK1 and the activation of the PLK1-Mps1 pathway. DAB2IP interacts with Cdc20 in a phosphorylation-independent manner. However, the phosphorylation of DAB2IP inhibits the ubiquitylation of Cdc20 in response to SAC, and blocks the premature release of the APC/C-MCC. The PLK1-Mps1 pathway plays an important role in mitotic checkpoint complex (MCC) assembly. It is likely that DAB2IP acts as a scaffold to aid PLK1-Mps1 in targeting Cdc20. Depletion or loss of the Cdks-mediated phosphorylation of DAB2IP destabilizes the MCC, impairs the SAC, and increases chromosome missegregation and subsequent CIN, thus contributing to tumorigenesis. Collectively, these results demonstrate the mechanism of DAB2IP in SAC regulation and provide a rationale for targeting the SAC to cause lethal CIN against DAB2IP-deficient aggressive PCa, which exhibits a weak SAC.

DAB2IP decreases cell growth and migration and increases sensitivity to chemotherapeutic drugs in colorectal cancer

Background

Colorectal cancer (CRC) is one of the most common cancers worldwide with high rates of invasiveness and mortality. DAB2IP (DOC2/DAB2 interactive protein) is a member of the RAS-GTPase-activating protein (RAS-GAP) family that shows a suppressive effect on cancer progression, is downregulated in several cancers. However, the role of DAB2IP in CRC remains elusive.

Methods

Expression of DAB2IP was evaluated in human CRC tissues using immunohistochemistry (IHC), quantitative real-time reverse transcription PCR (qRT-PCR) and immunoblotting. Knockdown and overexpression of DAB2IP in CRC cells were achieved by transfecting siRNAs and DAB2IP expression vectors and assessed by qRT-PCR and immunoblotting. CCK-8, colony formation, wound-healing, and transwell assays were used to evaluate CRC cell growth, migration, and sensitivity to chemotherapeutic drugs. The cell cycle was analyzed by propidium iodide (PI) staining and flow cytometry. Cell apoptosis was evaluated by Annexin V-DAPI double staining and flow cytometry. The effect of DAB2IP overexpression on tumor formation was explored by an in vivo tumorigenesis assay. Finally, immunoblotting was performed to examine the molecules related to the action of DAB2IP in CRC.

Results

Compared with para-cancer tissues, there was a marked decrease of DAB2IP expression in surgically excised CRCs. In cultured CRC cells, enforced expression of DAB2IP inhibited cell growth and migration and sensitized the cells to DNA-acting cisplatin, oxaliplatin, and doxorubicin but not 5-fluorouracil (5-FU). In contrast, knockdown of DAB2IP produced the opposite effect. Moreover, DAB2IP overexpression hindered tumor growth in vivo. We further found that DAB2IP regulated the expression of cell growth, epithelial-mesenchymal transition (EMT), and apoptosis-related proteins in CRC cells and inhibited the phosphorylation of protein kinase B (AKT) and extracellular signal-regulated kinase (ERK).

Conclusions

Expression of DAB2IP inhibited CRC cell growth and migration and sensitized CRC cells to chemotherapeutic drugs. Inhibition of the phosphorylation of AKT and ERK is associated with the effects of DAB2IP expression. Restoration of DAB2IP expression may be a novel target for treating CRC.

Overexpression of secretory clusterin (sCLU) induces chemotherapy resistance in human gastric cancer cells by targeting miR-195-5p

Recent focus has turned to secretory clusterin (sCLU) as a key contributor to chemoresistance of anticancer agents, but the role of sCLU on chemotherapy drug response to gastric cancer cells is not fully understood. Previous research found that sCLU was overexpressed in the induced multidrug-resistant MGC-803/5-FU cell line, suggesting that sCLU upregulation was closely related to chemoresistance to anticancer agents. In the present study, we aimed to clarify the role and mechanisms of sCLU in regulating the chemoresistance of gastric cancer cells. Cell apoptosis and cell viability were evaluated by annexin V/propidium iodide staining and CCK8. Expression of sCLU and miR-195-5P was detected using quantitative RT-PCR assays. The expression of sCLU in gastric cancer tissues was detected by RT-PCR assays. Upregulating or downregulating sCLU or miR-195-5P in gastric cancer cells was used to evaluate the mechanisms of chemoresistance. We found that sCLU was significantly elevated in the MGC-803/5-FU and SGC-7901 cells, and the downregulating sCLU sensitized MGC-803/5-FU and SGC-7901 cells to cisplatin and Docetaxel by upregulation of miR-195-5P. Upregulating sCLU in MGC-803 and HGC-27 cells was resistant to cisplatin and Docetaxel by downregulating miR-195-5p. Targeting miR-195-5P reduced the sensitivity of MGC-803 cells to 5-FU, and miR-195-5P overexpression enhanced the sensitivity of MGC-803/5-FU cells to 5-FU. The overexpression of sCLU in gastric cancer tissues was associated with chemoresistance. Our findings suggest that overexpression of sCLU induced chemoresistance in gastric cancer cells by downregulating miR-195-5p, thus providing a potential target for the development of agents that targeting sCLU for gastric cancer therapy.

Loss of DAB2IP Contributes to Cell Proliferation and Cisplatin Resistance in Gastric Cancer

Objective

Resistance to chemotherapeutic drugs, such as cisplatin, has been one of the major problems adversely affecting the clinical prognosis of patients with gastric cancer (GC). Disabled Homolog 2-Interacting Protein (DAB2IP) status is one of the major factors involved in sensitivity to chemotherapy in multiple cancer types. In the present study, we aimed to investigate the potential roles of DAB2IP in GC cell proliferation and cisplatin resistance.

Materials and Methods

DAB2IP expression was detected in human GC tissues using immunohistochemistry (IHC). The role of DAB2IP in regulating GC cell proliferation and cisplatin resistance was explored by genetic manipulation. Western blot analysis was used to determine the molecular signaling to explain the mechanism of the observed DAB2IP effects in GC.

Results

DAB2IP expression was downregulated in human GC tissues and low DAB2IP expression predicted poor prognosis. Moreover, our data provided evidence that DAB2IP upregulation impaired cell proliferation property and sensitized GC cells to cisplatin while DAB2IP depletion possessed the opposite effects. Mechanistically, we showed that DAB2IP could inhibit the phosphorylation and activation of protein kinase B (AKT) and extracellular signal-regulated kinase (ERK), and the enhanced proliferation ability induced by DAB2IP knockdown was greatly impaired after incubation with AKT or ERK inhibitor.

Conclusion

DAB2IP modulates GC cell proliferation and sensitivity to cisplatin potentially via regulation of AKT and ERK signaling pathway, indicating that DAB2IP may serve as a potential prognostic biomarker and therapeutic target for treatment of GC.

Down-regulation of autophagy-associated protein increased acquired radio-resistance bladder cancer cells sensitivity to taxol

BACKGROUND

As a bladder-preserving therapy, radiation therapy (RT) has been widely used in the treatment of bladder cancer (BCa) and made great progress in the past few decades. However, some BCa patients have low RT responsiveness and local recurrence rate after RT could reach 50%. Acquired radio-resistance (ARR) is one of the important reasons for the failure of RT. Unfortunately, these ARR cells also lack sensitivity to chemotherapy and cause tumor recurrence and metastasis.

PURPOSE

To build ARR-phenotype BCa cell model, discuss the possible molecular mechanism of ARR and find effective target molecules to overcome ARR.

MATERIALS AND METHODS

Five thousand six hundred and thirty-seven cells were subjected 30 times to 2 Gy of γ-rays and the surviving cells were called 5637R. Colony formation and MTT assay were applied to evaluate cells sensitivity to ionizing radiation (IR) and anti-neoplastic agents, respectively. Cells abilities of migration and invasion were determined using transwell method. Quantitative real-time polymerase chain reaction (RT-qPCR) and western blot (WB) were respectively utilized to compare the difference of gene and protein expression between 5637 and 5637R cells. Molecule inhibitors and small interfering RNA (siRNA) systems were employed to decrease the expression of target proteins, respectively.

RESULTS

BCa cells survived from fractionated irradiation (FI) exhibited tolerance to both IR and chemotherapy drugs. These ARR cells (5637R) had elevated migration and invasion abilities, accompanied by increased expression of epithelial mesenchymal transition (EMT)-related transcription factors (ZEB1/Snail/Twist). Moreover, 5637R cells showed enhanced cancer stem cell (CSC)-like characteristics with activated KMT1A-GATA3-STAT3 circuit, a newly reported self-renewal pathway of human bladder cancer stem cell (BCSC). Combined with Kaplan-Meier's analysis, we speculated that GATA3/MMP9/STAT3 could be an effective molecular panel predicting poor prognosis of BCa. In order to enhance the sensitivity of resistant cells to radiation, we introduced ERK inhibitor (FR 180204) and STAT3 inhibitor (S3I-201). However, both of them could not enhance ARR cells response to IR. On the other hand, siRNAs were respectively implemented to inhibit the expression of endogenous Beclin1 and Atg5, two important autophagy-related genes, in BCa cells, which significantly increased 5637R cells death upon taxol exposing. Similarly, chloroquine (CQ), a classic autophagy inhibitor, enhanced the cytotoxicity of taxol only on 5637R cells.

CONCLUSIONS

Long-term FI treatment is an effective method to establish the ARR-phenotype BCa cell model, by enriching BCSCs and enhancing cells migration and invasion. Both inhibiting the expression of autophagy-related proteins and using autophagy inhibitor can increase the sensitivity of ARR cells to taxol, suggesting that autophagy may play an important role in ARR cells chemical tolerance.

Upregulation of DAB2IP Inhibits Ras Activity and Tumorigenesis in Human Pancreatic Cancer Cells

KRAS mutation-induced Ras activation plays an important role in the pathogenesis of pancreatic cancer, but the role of wild-type Ras and Ras GTPase-activating proteins remains unclear. The present study was designed to determine the expression spectra of Ras GTPase-activating proteins genes in pancreatic cancer cells, and the role of DAB2IP, a Ras GTPase-activating proteins gene, in the development and progression of pancreatic cancer. Following the analyses of the expression profiles of 16 Ras GTPase-activating proteins in 6 pancreatic cancer cell lines including Bxpc-3 (with wild-type KRAS), Capan-2, Sw1990, Aspc-1, CFPAC-1, and Panc-1 (with mutant KRAS) and 1 normal human pancreatic ductal epithelial cell line, H6C7, the expression of DAB2IP messenger RNA was further analyzed by quantitative real-time polymerase chain reaction. The role of DAB2IP in pancreatic cancer was further investigated in vitro and in vivo by upregulating DAB2IP in Bxpc-3 cells through transfection of DAB2IP into Bxpc-3 cells with recombinant lentivirus. The DAB2IP expression in pancreatic cancer cells and tissues with wild-type KRAS was significantly lower than that in cells and tissues with mutant KRAS (P < .05). In Bxpc-3 cells with wild-type KRAS, overexpression of DAB2IP decreased the expression of P-AKT and P-ERK and the Ras activity; increased the expression of P-JNK and caspase 3; inhibited cell proliferation, invasiveness, and migration; and increased the cell sensitivity to cetuximab. Overexpression of DAB2IP inhibited tumor progression in a mouse model. In conclusion, DAB2IP downregulates Ras activity in wild-type pancreatic cancer cells. Overexpression of DAB2IP decreases the Ras activity, inhibits cell proliferation, and increases sensitivity to cetuximab in wild-type pancreatic cancer cells. In conclusion, DAB2IP may serve as a potential molecular therapeutic target for the treatment of pancreatic cancer.

Wnt/β-catenin signaling pathway induces autophagy-mediated temozolomide-resistance in human glioblastoma

Temozolomide (TMZ) is widely used for treating glioblastoma multiforme (GBM), however, the treatment of such brain tumors remains a challenge due to the development of resistance. Increasing studies have found that TMZ treatment could induce autophagy that may link to therapeutic resistance in GBM, but, the precise mechanisms are not fully understood. Understanding the molecular mechanisms underlying the response of GBM to chemotherapy is paramount for developing improved cancer therapeutics. In this study, we demonstrated that the loss of DOC-2/DAB2 interacting protein (DAB2IP) is responsible for TMZ-resistance in GBM through ATG9B. DAB2IP sensitized GBM to TMZ and suppressed TMZ-induced autophagy by negatively regulating ATG9B expression. A higher level of ATG9B expression was associated with GBM compared to low-grade glioma. The knockdown of ATG9B expression in GBM cells suppressed TMZ-induced autophagy as well as TMZ-resistance. Furthermore, we showed that DAB2IP negatively regulated ATG9B expression by blocking the Wnt/β-catenin pathway. To enhance the benefit of TMZ and avoid therapeutic resistance, effective combination strategies were tested using a small molecule inhibitor blocking the Wnt/β-catenin pathway in addition to TMZ. The combination treatment synergistically enhanced the efficacy of TMZ in GBM cells. In conclusion, the present study identified the mechanisms of TMZ-resistance of GBM mediated by DAB2IP and ATG9B which provides insight into a potential strategy to overcome TMZ chemo-resistance.

Secretory clusterin promotes hepatocellular carcinoma progression by facilitating cancer stem cell properties via AKT/GSK-3β/β-catenin axis

Background

To explore the modulatory effects and mechanism of secretory clusterin (sCLU) on cancer stem cell (CSC) properties in hepatocellular carcinoma (HCC).

Methods

The effects of sCLU repression or overexpression on chemoresistance, migration, invasion, and tumor growth were detected by MTT, wound healing, transwell assays, and xenograft assay, respectively. The tumor sphere assay was performed to evaluate the self-renewal ability of HCC cells. In addition, the molecular regulation between sCLU and AKT/GSK-3β/β-catenin axis in HCC cells were discovered by western blotting, quantitative real-time PCR (qRT-PCR), and immunofluorescence. The expression status of sCLU and β-catenin in HCC tissues were investigated by immunohistochemistry.

Results

Knockdown or overexpressing sCLU remarkably inhibited or promoted the chemoresistance against sorafenib/doxorubicin, metastasis, and tumor growth of HCC cells, respectively. HepG2 and HCCLM3-derived spheroids showed higher expression of sCLU than that in attached cells. Additionally, repressing sCLU impaired the self-renewal capacity of HCC cells and CSC-related chemoresistance while overexpression of sCLU enhanced these CSC properties. Knockdown or overexpression of sCLU inhibited or increased the expressions of β-catenin, cyclinD1, MMP-2 and MMP-9, and the phosphorylation of AKT or GSK3β signaling, respectively. However, LiCl or LY294002 abrogated the effects mediated by sCLU silencing or overexpression on chemoresistance, metastasis, and CSC phenotype. Furthermore, co-expression of sCLU and β-catenin in HCC tissues indicated poor prognosis of HCC patients.

Conclusions

Taken together, the oncogenic sCLU might promote CSC phenotype via activating AKT/GSK3β/β-catenin axis, suggesting that sCLU was a potential molecular-target for HCC therapy.

miR-92b promotes gastric cancer growth by activating the DAB2IP-mediated PI3K/AKT signalling pathway

Objectives

miR‐92b has been reported to play critical roles in several carcinomas; however, our understanding of the mechanisms by which miR‐92b stimulates gastric cancer (GC) is incomplete. The aim of this study was to investigate the clinical significance and functional relevance of miR‐92b in GC.

Materials and methods

Expression of miR‐92b in GC and peritumoural tissues was determined using qRT‐PCR, in situ hybridization and bioinformatics. CCK‐8, colony formation and fluorescence‐activated cell sorting assays were utilized to explore the effect of miR‐92b on GC cells. A luciferase reporter assay and Western blotting were employed to verify miR‐92b targeting of DAB2IP. Furthermore, Western blotting was used to evaluate the levels of DAB2IP and PI3K/Akt signalling pathway‐related proteins.

Results

In this study, we found that miR‐92b was upregulated in GC tissues compared with peritumoural tissues. Overexpression of miR‐92b promoted cell proliferation, colony formation, and G₀/G₁ transition and decreased apoptosis. Our results indicated that miR‐92b repressed the expression of DAB2IP and that loss of DAB2IP activated the PI3K/AKT signalling pathway. Overexpression of DAB2IP rescued the effects of miR‐92b in GC cells. Finally, our results demonstrated a significant correlation between miR‐92b expression and DAB2IP expression in GC tissues.

Conclusions

Our results suggest that miR‐92b promotes GC cell proliferation by activating the DAB2IP‐mediated PI3K/AKT signalling pathway. The miR‐92b/DAB2IP/PI3K/AKT signalling axis may be a potential therapeutic target to prevent GC progression.

Development of 3D Lymph Node Mimetic for Studying Prostate Cancer Metastasis

Lymph node (LN) metastasis causes poor prognosis for patients with prostate cancer (PCa). Although LN-cells and cellular responses play a pivotal role in cancer metastasis, the interplay between LN-cells and PCa cells is undetermined due to the small size and widespread distribution of LNs. To identify factors responsible for LN metastasis, a 3D cell culture biosystem is fabricated to simulate LN responses during metastasis. First, it is determined that LN explants previously exposed to high metastatic PCa release substantially more chemotactic factors to promote metastatic PCa migration than those exposed to low-metastatic PCa. Furthermore, T-lymphocytes are found to produce chemotactic factors in LNs, among which, CXCL12, CCL21, and IL-10 are identified to have the most chemotactic effect. To mimic the LN microenvironment, Cytodex beads are seeded with T cells to produce a LN-mimetic biosystem in both static and flow conditions. As expected, the flow condition permits prolonged cellular responses. Interestingly, when PCa cells with varying metastatic potentials are introduced into the system, it produces PCa-specific chemokines accordingly. These results support that the LN mimetic helps in analyzing the processes underlying metastasized LNs and for testing various treatments to reduce cancer LN metastasis.

Soft fibrin matrix downregulates DAB2IP to promote Nanog-dependent growth of colon tumor-repopulating cells

Colon cancer stem cells (CSCs) have been shown to be responsible for the recurrence and metastasis of colorectal cancer (CRC). As a crucial microenvironmental factor, extracellular matrix (ECM) stiffness is known to affect the stemness of CSCs. Recently, fibrin deposition in the stroma of CRC was demonstrated to be responsible for tumor development. In this study, we used salmon fibrin gel to provide a 3D ECM for colon cancer cells and investigated its effects on cell growth as well as the underlying mechanisms. Compared with stiff 420 Pascal (Pa) and 1 050 Pa gels, 90 Pa soft fibrin gel was most efficient at isolating and enriching tumor colonies. The size and number of colony formation negatively correlated with gel stiffness. Specifically, these tumor colonies exhibited efficient tumorigenicity, upregulated stem cell markers, and had anti-chemotherapeutic properties and were thus named tumor-repopulating cells (TRCs). More importantly, the self-renewal molecule Nanog was sharply induced in 3D-cultured colon TRCs; further, Nanog siRNA significantly inhibited colony formation, suggesting the indispensable role of Nanog in TRC growth. A subsequent mechanistic study illustrated that Nanog expression could be modulated through fibrin gel stiffness-induced DAB2IP/PI3K/FOXA1 signaling in colon TRCs.

Antrocin Sensitizes Prostate Cancer Cells to Radiotherapy through Inhibiting PI3K/AKT and MAPK Signaling Pathways

Radiotherapy is one of the most common treatment options for local or regional advanced prostate cancer (PCa). Importantly, PCa is prone to radioresistance and often develops into malignancies after long-term radiotherapy. Antrocin, a sesquiterpene lactone isolated from Antrodia cinnamomea, possesses pharmacological efficacy against various cancer types; however, its therapeutic potential requires comprehensive exploration, particularly in radioresistant PCa cells. In this study, we emphasized the effects of antrocin on radioresistant PCa cells and addressed the molecular mechanism underlying the radiosensitization induced by antrocin. Our results showed that a combination treatment with antrocin and ionizing radiation (IR) synergistically inhibited cell proliferation and induced apoptosis in radioresistant PCa cells. We further demonstrated that antrocin downregulated PI3K/AKT and MAPK signaling pathways as well as suppressed type 1 insulin-like growth factor 1 receptor (IGF-1R)-mediated induction of β-catenin to regulate cell cycle and apoptosis. Using xenograft mouse models, we showed that antrocin effectively enhanced radiotherapy in PCa. Our study demonstrates that antrocin sensitizes PCa to radiation through constitutive suppression of IGF-1R downstream signaling, revealing that it can be developed as a potent therapeutic agent to overcome radioresistant PCa.

Genetics and biology of prostate cancer

Despite the high long-term survival in localized prostate cancer, metastatic prostate cancer remains largely incurable even after intensive multimodal therapy. The lethality of advanced disease is driven by the lack of therapeutic regimens capable of generating durable responses in the setting of extreme tumor heterogeneity on the genetic and cell biological levels. Here, we review available prostate cancer model systems, the prostate cancer genome atlas, cellular and functional heterogeneity in the tumor microenvironment, tumor-intrinsic and tumor-extrinsic mechanisms underlying therapeutic resistance, and technological advances focused on disease detection and management. These advances, along with an improved understanding of the adaptive responses to conventional cancer therapies, anti-androgen therapy, and immunotherapy, are catalyzing development of more effective therapeutic strategies for advanced disease. In particular, knowledge of the heterotypic interactions between and coevolution of cancer and host cells in the tumor microenvironment has illuminated novel therapeutic combinations with a strong potential for more durable therapeutic responses and eventual cures for advanced disease. Improved disease management will also benefit from artificial intelligence-based expert decision support systems for proper standard of care, prognostic determinant biomarkers to minimize overtreatment of localized disease, and new standards of care accelerated by next-generation adaptive clinical trials.

Disabled homolog 2 interactive protein functions as a tumor suppressor in osteosarcoma cells

The disabled homolog 2 interactive protein (DAB2IP) gene is a member of the family of Ras GTPases and functions as a tumor suppressor in many types of carcinoma; however, its function in osteosarcoma remains unclear. The aim of the present study was to determine the function of DAB2IP in osteosarcoma and normal bone cells in vitro. The expression of DAB2IP protein was assessed in osteoblast and osteosarcoma cell lines by western blot analysis. The effects of DAB2IP expression on cell proliferation, colony formation, apoptosis, cell cycle, and cell migration and invasion were evaluated by in vitro studies. DAB2IP expression was lower in osteosarcoma cell lines than in normal osteoblast cell lines. DAB2IP expression affected cell proliferation, apoptosis and cell cycle distribution. In addition, DAB2IP inhibited the migration and invasion of osteosarcoma and normal osteoblast cells. Therefore, DAB2IP may function as a tumor suppressor in osteosarcoma cell lines by inhibiting cell proliferation and invasion.

DC-CIK cells derived from ovarian cancer patient menstrual blood activate the TNFR1-ASK1-AIP1 pathway to kill autologous ovarian cancer stem cells

Ovarian cancer stem cells (OCSCs) are highly carcinogenic and have very strong resistance to traditional chemotherapeutic drugs; therefore, they are an important factor in ovarian cancer metastasis and recurrence. It has been reported that dendritic cell (DC)-cytokine-induced killer (CIK) cells have significant killing effects on all cancer cells across many systems including the blood, digestive, respiratory, urinary and reproductive systems. However, whether DC-CIK cells can selectively kill OCSCs is currently unclear. In this study, we collected ovarian cancer patient menstrual blood (OCPMB) samples to acquire mononuclear cells and isolated DC-CIK cells in vitro. In addition, autologous CD44+/CD133+ OCSCs were isolated and used as target cells. The experimental results showed that when DC-CIK cells and OCSCs were mixed and cultured in vitro at ratios of 5:1, 10:1 and 50:1, the DC-CIK cells killed significant amounts of OCSCs, inhibited their invasion in vitro and promoted their apoptosis. The qPCR and Western blot results showed that DC-CIK cells stimulated high expression levels and phosphorylation of TNFR1, ASK1, AIP1 and JNK in OCSCs through the release of TNF-α. After the endogenous TNFR1 gene was knocked out in OCSCs using the CRISPR/Cas9 technology, the killing function of DC-CIK cells on target OCSCs was significantly attenuated. The results of the analyses of clinical samples suggested that the TNFR1 expression level was negatively correlated with ovarian cancer stage and prognosis. Therefore, we innovatively confirmed that DC-CIK cells derived from OCPMB could secret TNF-α to activate the expression of the TNFR1-ASK1-AIP1-JNK pathway in OCSCs and kill autologous OCSCs.

Simvastatin Sensitizes Radioresistant Prostate Cancer Cells by Compromising DNA Double-Strand Break Repair

Prostate cancer (PCa) is one of the most prevalent male cancers in western world. Radiation therapy (RT) is commonly used to treat PCa patients. However, a certain proportion of patients develop radioresistant PCa cells, which results in metastatic disease. Statins, which inhibit 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase, are commonly used to treat hypercholesterolemia, exhibiting beneficial effects on cardiovascular diseases and on several types of cancers, including PCa. However, the mechanistic details and crosstalk between statins and RT in PCa cells remain unknown. In this study, radioresistant DOC-2/DAB2 interactive protein (DAB2IP)-deficient PCa cells were used to evaluate whether simvastatin could enhance the effect of ionizing radiation (IR). The crucial molecules that associated with simvastatin elevated radiosensitivity in PCa cells were explored. Our results demonstrated that a combination treatment with simvastatin and IR synergistically induced apoptosis of radioresistant PCa cells. In addition, simvastatin appeared to compromise DNA double-strand breaks repair by activating the expressions of histone 2A family member X (γ-H2AX) and phospho-checkpoint kinase 1 (p-CHK1), suggesting an underlying mechanism for this radiosensitization of PCa cells. These findings reveal that simvastatin may be a potent therapeutic agent for co-treatment with radiation to overcome radioresistance in PCa cells.

DAB2IP Downregulation Enhances the Proliferation and Metastasis of Human Gastric Cancer Cells by Derepressing the ERK1/2 Pathway

DAB2IP (DOC2/DAB2 interactive protein) is downregulated in several cancer types, and its downregulation is involved in tumor cell proliferation, apoptosis, metastasis, and epithelial-mesenchymal transition (EMT). We aimed to investigate the potential role of DAB2IP in the development and progression of gastric cancer. DAB2IP levels were analyzed in human gastric cancer and adjacent normal tissues by Western blots and immunohistochemistry. Potential roles of DAB2IP in regulating gastric cancer cell growth and metastasis were examined by genetic manipulation in vitro. The molecular signaling was determined to understand the mechanisms of observed DAB2IP effects. DAB2IP level is lower in gastric cancer tissues as compared to paired normal tissues. Knockdown of DAB2IP enhanced gastric cancer cell growth and metastasis in vitro and promoted EMT progress at both protein and mRNA levels. Silencing DAB2IP activated extracellular signal-regulated kinase 1/2 (ERK1/2) pathway, and the enhanced proliferation and migration ability induced by DAB2IP knockdown were reduced after incubation with U0126 in SGC7901 gastric cancer cells. Inhibition of DAB2IP enhances gastric cancer cell growth and metastasis through targeting the ERK1/2 signaling, indicating that it may serve as a potential target for treatment of gastric cancer.

Systematic identification of functionally relevant risk alleles to stratify aggressive versus indolent prostate cancer

Novel approaches for classification, including molecular features, are needed to direct therapy for men with low-grade prostate cancer (PCa), especially men on active surveillance. Risk alleles identified from genome-wide association studies (GWAS) could improve prognostication. Those risk alleles that coincided with genes and somatic copy number aberrations associated with progression of PCa were selected as the most relevant for prognostication.

In a systematic literature review, a total of 698 studies were collated. Fifty-three unique SNPs residing in 29 genomic regions, including 8q24, 10q11 and 19q13, were associated with PCa progression. Functional studies implicated 21 of these single nucleotide polymorphisms (SNPs) as modulating the expression of genes in the androgen receptor pathway and several other oncogenes. In particular, 8q24, encompassing MYC, harbours a high density of SNPs conferring unfavourable pathological characteristics in low-grade PCa, while a copy number gain of MYC in low-grade PCa was associated with prostate-specific antigen recurrence after radical prostatectomy.

By combining GWAS data with gene expression and structural rearrangements, risk alleles were identified that could provide a new basis for developing a prognostication tool to guide therapy for men with early prostate cancer.

Validation of DAB2IP methylation and its relative significance in predicting outcome in renal cell carcinoma

We have recently reported tumor suppressive role of DAB2IP in RCC development. In this study, We identified one CpG methylation biomarker (DAB2IP CpG1) located UTSS of DAB2IP that was associated with poor overall survival in a cohort of 318 ccRCC patients from the Cancer Genome Atlas (TCGA). We further validated the prognostic accuracy of DAB2IP CpG methylation by pyrosequencing quantitative methylation assay in 224 ccRCC patients from multiple Chinese centers (MCHC set), and 239 patients from University of Texas Southwestern Medical Center at Dallas (UTSW set) by using FFPE samples. DAB2IP CpG1 can predict the overall survival of patients in TCGA, MCHC, and UTSW sets independent of patient age, Fuhrman grade and TNM stage (all p<0.05). DAB2IP CpG1 successfully categorized patients into high-risk and low-risk groups with significant differences of clinical outcome in respective clinical subsets, regardless of age, sex, grade, stage, or race (HR: 1.63-7.83; all p<0.05). The detection of DAB2IP CpG1 methylation was minimally affected by ITH in ccRCC. DAB2IP mRNA expression was regulated by DNA methylation in vitro. DAB2IP CpG1 methylation is a practical and repeatable biomarker for ccRCC, which can provide prognostic value that complements the current staging system.

Upregulating DAB2IP expression via EGR-1 inhibition, a new approach for overcoming fractionated-irradiation-induced cross-tolerance to ionizing radiation and mitomycin C in tumor cells

PURPOSE

To evaluate the effect of fractionated irradiation (FI) on tumor cells' sensitivity to ionizing radiation (IR) and antineoplastic drugs, and examine the potential of early growth response-1 (EGR-1) inhibition to sensitize tumor cells to IR.

MATERIALS AND METHODS

PC3 and HepG2 cells were subjected 10 times to γ-rays at 2 Gy. The surviving cells were named PC3/R and HepG2/R, respectively. The cells' sensitivity to irradiation and chemotherapeutic drugs, including cisplatin (PT), doxorubicin (DOX), mitomycin C (MMC) and 5-fluorouracil (5-FU), were identified by colony formation assay and MMT method, respectively. Quantitative real-time polymerase chain reaction (RT-qPCR) analysis was utilized to compare the difference of gene expression between radioresistant cells and parental cells. The small interfering RNA system was implemented to inhibit endogenous EGR-1 expression in radiation-resistant cells. Western blot was employed to identify the possible mechanism by which EGR-1 regulates cells' radiosensitivity.

RESULTS

FI induced cross-resistant to IR and MMC in tumor cells. Along with the reduction of ovarian cancer-2/disabled homolog 2 (DOC-2/DAB2) interactive protein (DAB2IP) expression, EGR-1 gene was upregulated in FI-treated cells. On the other hand, downregulation of EGR-1 gene expression sensitized radioresistant cells to IR accompanied by DAB2IP overexpression and STAT3 inactivation. In addition, NF-κB inhibitor, BAY11-7082 enhanced resistant cells' radiosensitivity and chemosensitivity.

CONCLUSIONS

Conventionally FI has a higher risk of forming acquired radioresistance (ARR) in vitro. EGR-1 gene-targeted drug design could be an effective strategy to overcome DAB2IP-dysregulation-induced ARR in tumor patients.

Alternative Splicing of EZH2 pre-mRNA by SF3B3 Contributes to the Tumorigenic Potential of Renal Cancer

Purpose: Deregulation or mutation of the EZH2 gene causes various tumors, including clear cell renal cell carcinoma (ccRCC). Although several splice variants of EZH2 have been identified, little is known about how EZH2 splicing is regulated or the contribution of alternative splicing to its protumorigenic functions.Experimental Design: We conducted RT-PCR, Western blot analysis, and IHC techniques to examine EZH2 and its alternative splicing transcript expression in renal cancer tissue and renal cancer cell lines. Proliferation, migration, clonogenicity, and tumorigenicity of renal cancer cells either exhibiting knockdown of EZH2 or its splicing factor SF3B3 were assessed by CCK8, Transwell assay, and murine xenograft experiments.Results: We found that the inclusion of alternative EZH2 exon 14 was significantly increased in ccRCC samples and renal cancer cell lines. In ccRCC lines, enforced expression of EZH2Δ14 inhibited, and EZH2 promoted, cell growth, migration, proliferation, and tumorigenicity in a xenograft model. Mechanistic studies demonstrated that EZH2Δ14 isoform functions as a dominant-negative inhibitor of full-length EZH2. Coexpression of EZH2Δ14 variant with full-length EZH2 not only abrogated DAB2IP and HOXA9 suppression but also inhibited EZH2-driven tumorigenesis. Strikingly, the splicing factor SF3B3 stimulates inclusion of exon14 and has pro-proliferative activity. Importantly, the upregulation of SF3B3 expression observed in clinical ccRCC samples parallels the increased inclusion of EZH2 exon14, and the SF3B3 level is associated with higher tumor stage and poor overall survival.Conclusions: These results suggest SF3B3 as a key regulator of EZH2 pre-mRNA splicing and SF3B3 may represent a novel prognostic factor and potential therapeutic target in ccRCC. Clin Cancer Res; 23(13); 3428-41. ©2016 AACR.

Block one, unleash a hundred. Mechanisms of DAB2IP inactivation in cancer

One of the most defining features of cancer is aberrant cell communication; therefore, a molecular understanding of the intricate network established among tumor cells and their microenvironment could significantly improve comprehension and clinical management of cancer. The tumor suppressor DAB2IP (Disabled homolog 2 interacting protein), also known as AIP1 (ASK1 interacting protein), has an important role in this context, as it modulates signal transduction by multiple inflammatory cytokines and growth factors. DAB2IP is a Ras-GAP, and negatively controls Ras-dependent mitogenic signals. In addition, acting as a signaling adaptor, DAB2IP modulates other key oncogenic pathways, including TNFα/NF-κB, WNT/β-catenin, PI3K/AKT, and androgen receptors. Therefore, DAB2IP inactivation can provide a selective advantage to tumors initiated by a variety of driver mutations. In line with this role, DAB2IP expression is frequently impaired by methylation in cancer. Interestingly, recent studies reveal that tumor cells can employ other sophisticated mechanisms to disable DAB2IP at the post-transcriptional level. We review the mechanisms and consequences of DAB2IP inactivation in cancer, with the purpose to support and improve research aimed to counteract such mechanisms. We suggest that DAB2IP reactivation in cancer cells could be a strategy to coordinately dampen multiple oncogenic pathways, potentially limiting progression of a wide spectrum of tumors.

DAB2IP in cancer

DOC-2/DAB2 is a member of the disable gene family that features tumor-inhibiting activity. The DOC-2/DAB2 interactive protein, DAB2IP, is a new member of the Ras GTPase-activating protein family. It interacts directly with DAB2 and has distinct cellular functions such as modulating different signal cascades associated with cell proliferation, survival, apoptosis and metastasis. Recently, DAB2IP has been found significantly down regulated in multiple types of cancer. The aberrant alteration of DAB2IP in cancer is caused by a variety of mechanisms, including the aberrant promoter methylation, histone deacetylation, and others. Reduced expression of DAB2IP in neoplasm may indicate a poor prognosis of many malignant cancers. Moreover, DAB2IP stands for a promising direction for developing targeted therapies due to its capacity to inhibit tumor cell growth in vitro and in vivo. Here, we summarize the present understanding of the tumor suppressive role of DAB2IP in cancer progression; the mechanisms underlying the dysregulation of DAB2IP; the gene functional mechanism and the prospects of DAB2IP in the future cancer research.

Tumor suppressor protein DAB2IP participates in chromosomal stability maintenance through activating spindle assembly checkpoint and stabilizing kinetochore-microtubule attachments

Defects in kinetochore-microtubule (KT-MT) attachment and the spindle assembly checkpoint (SAC) during cell division are strongly associated with chromosomal instability (CIN). CIN has been linked to carcinogenesis, metastasis, poor prognosis and resistance to cancer therapy. We previously reported that the DAB2IP is a tumor suppressor, and that loss of DAB2IP is often detected in advanced prostate cancer (PCa) and is indicative of poor prognosis. Here, we report that the loss of DAB2IP results in impaired KT-MT attachment, compromised SAC and aberrant chromosomal segregation. We discovered that DAB2IP directly interacts with Plk1 and its loss inhibits Plk1 kinase activity, thereby impairing Plk1-mediated BubR1 phosphorylation. Loss of DAB2IP decreases the localization of BubR1 at the kinetochore during mitosis progression. In addition, the reconstitution of DAB2IP enhances the sensitivity of PCa cells to microtubule stabilizing drugs (paclitaxel, docetaxel) and Plk1 inhibitor (BI2536). Our findings demonstrate a novel function of DAB2IP in the maintenance of KT-MT structure and SAC regulation during mitosis which is essential for chromosomal stability.

Construction of a luciferase reporter gene vector containing DAB2IP promoter

AIM

To construct and identify pGL3-Basic-DAB2IP-luc vector, a luciferase reporter gene vector containing DAB2IP promoter, and explore the regulatory effect of Snail on the activity of this promoter in gastric cancer cells.

METHODS

The fragment of DAB2IP gene promoter (1000 bp) was amplified by PCR and then cloned into pGL3-Basic-luc vector to obtain pGL3-Basic-DAB2IP-luc vector, which was identified by restriction enzyme digestion, sequencing and biological activity detection. The activity of pGL3-Basic-DAB2IP-luc and the expression of DAB2IP were detected after transfection with pEGFP-C1-Snail in gastric cancer cells.

RESULTS

Luciferase reporter system showed that the luciferase activity was significantly lower in the Snail + pGL3-Basic-DAB2IP-luc group compared to the pGL3-Basic-DAB2IP-luc group and blank group (P < 0.01 for both). In addition, the luciferase activity was significantly lower in the pGL3-Basic-DAB2IP-luc group than in the blank group (P < 0.01). Real-time PCR and Western blot results showed that mRNA and protein expression of DAB2IP was decreased in gastric cancer cells after transfection with pEGFP-C1-Snail.

CONCLUSION

The transcription factor Snail inhibits the transcription and expression of DAB2IP. The vector pGL3-Basic-DAB2IP-luc has been constructed successfully and its biological activity has been identified, which provides an important tool for further study of the role of DAB2IP in transcriptional regulation in gastric cancer.

DAB2IP regulates EMT and metastasis of prostate cancer through targeting PROX1 transcription and destabilizing HIF1α protein

Prospero-related homeobox 1 (PROX1) is an essential regulator in lymphangiogenesis and has been implicated in both oncogenic and tumor-suppressive functions in many types of human cancers. However, the role of PROX1 in prostate cancer (PCa) remains poorly understood. In this study, based on different PCa cell lines and knockout mice, we showed that PROX1 could be suppressed by DAB2IP, a novel member of the Ras GTPase-activating protein family and a critical player in control of epithelial-mesenchymal transition (EMT) and PCa metastasis. Mechanistically, PROX1 overexpression in DAB2IP-deficient PCa cells could enhance the accumulation of HIF1α protein by inhibiting ubiquitin pathway and then consequently induce an EMT response, which is characterized by repression of E-cadherin, up-regulation of vimentin and matrix metallopeptidases (MMPs) and enhancement of cell migration. Together, our data provides a new insight into mechanism that DAB2IP regulates EMT and PCa metastasis, especially points out the potential roles of its downstream PROX1/HIF1α signaling in a unique non-skeletal metastasis of PCa.

Decreased DAB2IP gene expression, which could be induced by fractionated irradiation, is associated with resistance to γ‑rays and α‑particles in prostate cancer cells

External beam radiation therapy, alone or combined with androgen deprivation, is a well‑established treatment for prostate cancer (PCa). However, not all patients benefit from radiotherapy due to congenital or acquired radioresistance. The preliminary results of the present study indicated that the loss of disabled homolog 2 interactive protein (DAB2IP) expression in PCa and normal prostate epithelia results in the resistance to γ‑rays. To further explore the association between DAB2IP and ionizing radiation (IR), PCa cells were fractionally irradiated 12 times with 2 Gy of γ‑rays and the change in DAB2IP mRNA expression was monitored. Notably, along with a continuous reduction of DAB2IP expression levels, increased expression levels of ataxia‑telangiectasia mutated (ATM) was observed in IR‑treated cells. In order to improve the sensitivity of DAB2IP‑deficient cells to IR, α‑particles, a type of high linear energy transfer radiation and KU55933, an ATM inhibitor, were used in the current study. It was determined that α‑particle irradiations were more effective than γ‑rays on cells expressing expected and decreased levels of DAB2IP. However, cells with a dysfunctional DAB2IP gene were resistant to α‑particle irradiation. Treatment with KU55933 did not enhance cell sensitivity to α‑irradiation. Therefore, this suggested that DAB2IP downregulation induced by radiotherapy may be associated with acquired radioresistance in patients with PCa.

Loss of DAB2IP expression in human urothelial carcinoma is associated with poorer recurrence-free survival

The purpose of this study is to investigate the clinical relevance of deletion of ovarian carcinoma 2/disabled homolog 2 (DOC-2/DAB2) interacting protein (DAB2IP) expression in human urothelial carcinoma (UC). We studied DAB2IP protein expression by immunohistochemistry in 130 UCs (90 of the bladder and 40 of the upper urinary tract) and 79 adjacent normal tissues and assessed its prognostic value in terms of recurrence-free and progression-free survival in superficial bladder UC. Twelve human UC cell lines were examined for DAB2IP messenger RNA (mRNA) and protein expression using quantitative RT-PCR and western blotting. Selected cell lines were used to study the effect of treatment with chromatin-modifying agents (5-aza-2'-deoxycytidine, Trichostatin A, or both) on DAB2IP expression. Of 90 bladder tumors, 50 (56 %) and, of 40 upper tract UC, 11 (28 %) were positive for DAB2IP immunostaining (bladder cancer versus upper tract UC, p = 0.003). In 65 superficial cases of bladder cancer loss of DAB2IP, expression was significantly associated with decreased recurrence-free survival (p = 0.046), but not with progression-free survival. Most human urothelial cancer cell lines consistently express DAB2IP mRNA and protein, without any relation to S-phase kinase protein expression. After treatment with either 5-aza-2'-deoxycytidine or Trichostatin A or both, the low DAB2IP-expressing bladder cancer cell lines BFTC905 and BFTC909 showed increased DAB2IP mRNA expression. DAB2IP protein levels are higher in bladder cancer than in upper tract UC and in superficial bladder cancer. This is associated with longer recurrence-free survival. Epigenetic regulation of DAB2IP protein appears to play an important role in human urothelial carcinoma.

Non-canonical GLI1/2 activation by PI3K/AKT signaling in renal cell carcinoma: A novel potential therapeutic target

Renal cell carcinoma (RCC) is the most lethal urologic malignancy; however, the molecular events supporting RCC carcinogenesis and progression remain poorly understood. In this study, based on the analysis of gene expression profile data from human clear cell RCC (ccRCC) and the corresponding normal tissues, we discovered that Hedgehog (HH) pathway component genes GLI1 and GLI2 were significantly elevated in ccRCC. Survival analysis of a large cohort of ccRCC samples demonstrated that the expression of GLI1 and GLI2 was negatively correlated with patient overall survival. Clinical sample-based VHL mutation and cell model-based VHL manipulation studies all indicated that the activation of GLI1 and GLI2 was not affected by VHL status. Further signaling pathway dissections demonstrated that GLI1 and GLI2 were activated by the phosphoinositide 3-kinase (PI3K)/AKT pathway, but not mediated by the canonical HH/SMO/GLI signaling. Up-regulation of GLI1 and GLI2 promoted RCC proliferation and clonogenic ability, whereas, a combination of GLIs inhibitor Gant61 and AKT inhibitor Perifosine synergistically suppressed RCC growth and induced apoptosis in vitro and in vivo. Therefore, this study identifies that GLI1 and GLI2 are critical for RCC carcinogenesis, and also provides an alternative therapeutic strategy for RCC.

DAB2IP loss confers the resistance of prostate cancer to androgen deprivation therapy through activating STAT3 and inhibiting apoptosis

Loss of DAB2IP, a novel tumor suppressor gene, is associated with the high risk of aggressive prostate cancer (PCa). Previously, we reported that DAB2IP modulated androgen receptor activation in the development of castration-resistant PCa; however, its direct action on the failure of androgen deprivation therapy (ADT) remains largely unknown. In this study, we showed that DAB2IP knockdown could significantly enhance in vitro growth and colony formation of PCa cells following ADT as well as tumorigenicity in pre-castrated nude mice. In addition, DAB2IP loss stabilized mitochondrial transmembrane potential, prevented release of cytochrome c, Omi/HtrA2 and Smac from the mitochondria to the cytoplasm and inhibited intrinsic apoptosis induced by ADT. Mechanistically, DAB2IP could interact with the signal transducer and activator of transcription 3 (STAT3) via its unique PR domain and suppress STAT3 phosphorylation and transactivation, leading to the inhibition of survivin expression in PCa cells. Moreover, the luminal epithelia in DAB2IP^−/− mice with more activated STAT3 and survivin expression were resistant to castration-induced apoptosis. Consistently, DAB2IP expression inversely correlated with STAT3 phosphorylation and survivin expression in PCa patients. Together, our data indicate that DAB2IP loss reprograms intracellular signal transduction and anti-apoptotic gene expression, which potentiates PCa cell survival from ADT-induced cell death.

Pretreatment biopsy analysis of DAB2IP identifies subpopulation of high-risk prostate cancer patients with worse survival following radiation therapy

Decreased expression of tumor suppressor DAB2IP is linked to aggressive cancer and radiation resistance in several malignancies, but clinical survival data is largely unknown. We hypothesized that pretreatment DAB2IP reduction would predict worse prostate cancer‐specific survival (PCSS). Immunohistochemistry of pretreatment biopsies was scored by an expert genitourinary pathologist. Other endpoints analyzed include freedom from biochemical failure (FFBF), castration resistance‐free survival (CRFS), and distant metastasis‐free survival (DMFS). Seventy‐nine patients with NCCN‐defined high‐risk prostate cancer treated with radiotherapy from 2005 to 2012 at our institution were evaluated. Twenty‐eight percent (22/79) of pretreatment biopsies revealed DAB2IP‐reduction. The median follow up times were 4.8 years and 5.3 years for patients in the DAB2IP‐reduced group and DAB2IP‐retained group, respectively. Patients with reduced DAB2IP demonstrated worse outcome compared to patients retaining DAB2IP, including FFBF (4‐year: 34 vs. 92%; P < 0.0001), CRFS (4‐year: 58 vs. 96%; P = 0.0039), DMFS (4‐year: 58 vs. 100%; P = 0.0006), and PCSS (5‐year: 83 vs. 100%; P = 0.0102). Univariate analysis showed T stage, N stage, and Gleason score were statistically significant variables. Pretreatment tumor DAB2IP status remained significant in multivariable analyses. This study suggests that about one‐fourth of men with high‐risk prostate cancer have decreased tumor expression of DAB2IP. This subpopulation with reduced DAB2IP has a suboptimal response and worse malignancy‐specific survival following radiation therapy and androgen deprivation. DAB2IP loss may be a genetic explanation for the observed differences in aggressive tumor characteristics and radiation resistance. Further study into improving treatment response and survival in this subpopulation is warranted.

DAB2IP regulates the chemoresistance to pirarubicin and tumor recurrence of non-muscle invasive bladder cancer through STAT3/Twist1/P-glycoprotein signaling

There is a high frequency of tumor recurrence in non-muscle invasive bladder cancer (NMIBC) after transurethral resection and postoperative intravesical chemotherapy, however, the molecular mechanisms leading to the chemoresistance and tumor re-growth remain largely unknown. In this study, we observed a significant decrease of DAB2IP expression in high-grade and recurrent NMIBC specimens, which was negatively correlated with Twist1 expression and predicted a lower recurrence-free survival of patients. Mechanistically, DAB2IP could inhibit the phosphorylation and transactivation of STAT3, and then subsequently suppress the expression of Twist1 and its target gene P-glycoprotein, both of which were crucial for the pirarubicin chemoresistance and tumor re-growth of bladder cancer cells. Overall, this study reveals a new promising biomarker modulating the chemoresistance and tumor recurrence of NMIBC after bladder preservation surgery.

A Versatile Monoclonal Antibody Specific Against Human DAB2IP

Human DAB2 interaction protein (DAB2IP) is a member of Ras-GTPase activating protein family and functions as a tumor suppressor, implying it could serve as a prognostic biomarker in cancers. Here we generated a mouse monoclonal antibody, 2A4, directed against human DAB2IP. This antibody was identified as IgG1 and specifically recognizes DAB2IP in both its native and denatured forms. It will serve as a useful and versatile tool for further mechanistic study and development of the potential prognostic significance of DAB2IP.

A Novel Monoclonal Antibody Against Human DAB2IP

DAB2 interactive protein (DAB2IP), also known as ASK1-interacting protein-1 (AIP1), a novel member of the RasGTPase-activating protein family, plays a key role in tumor suppression during cancer progression and is highly expressed in vascular smooth muscle cells (VSMCs) and endothelial cells (ECs). To further explore its function as a cancer suppressor, in this study, we immunized BALB/c mice with synthesized human DAB2IP polypeptide and obtained a novel monoclonal antibody (MAb) against human DAB2IP. A stable strain of hybridoma was screened and successfully established by the hybridoma technique. The immunohistochemistry, immunocytochemistry, and Western blot analysis revealed that the MAb was directed against human DAB2IP with high specificity. Therefore, this MAb may be a useful tool and facilitate studies on tumorigenesis associated with DAB2IP.

A literature mining-based approach for identification of cellular pathways associated with chemoresistance in cancer

Chemoresistance is a major obstacle to the successful treatment of many human cancer types. Increasing evidence has revealed that chemoresistance involves many genes and multiple complex biological mechanisms including cancer stem cells, drug efflux mechanism, autophagy and epithelial-mesenchymal transition. Many studies have been conducted to investigate the possible molecular mechanisms of chemoresistance. However, understanding of the biological mechanisms in chemoresistance still remains limited. We surveyed the literature on chemoresistance-related genes and pathways of multiple cancer types. We then used a curated pathway database to investigate significant chemoresistance-related biological pathways. In addition, to investigate the importance of chemoresistance-related markers in protein-protein interaction networks identified using the curated database, we used a gene-ranking algorithm designed based on a graph-based scoring function in our previous study. Our comprehensive survey and analysis provide a systems biology-based overview of the underlying mechanisms of chemoresistance.