DAB2IP associates with hereditary angioedema: Insights into the role of VEGF signaling in HAE pathophysiology.

BACKGROUND: In the recent years, there was an important improvement in the understanding of the pathogenesis of hereditary angioedema (HAE). Notwithstanding, in a large portion of patients with unknown mutation (HAE-UNK) the genetic cause remains to be identified. OBJECTIVES: To identify new genetic targets associated with HAE, a large Argentine family with HAE-UNK spanning 3 generations was studied. METHODS: Whole exome sequencing was performed on affected family members to identify potential genetic variants associated with HAE-UNK. In silico analyses and experimental studies were applied to assess the role of the identified gene variant. RESULTS: A missense variant (p.D239N) in DAB2IP was identified. The variant occurred in the C2-domain, the region interacting with vascular endothelial growth factor receptor 2 (VEGFR2). It was found to be rare, and predicted to have a detrimental effect on the functionality of DAB2IP. Protein structure modeling predicted changes in the mutant p.D239N protein structure, impacting protein stability. The p.D239N variant affected the subcellular localization of VEGFR2. Cells transfected with the DAB2IP-239N transcript exhibited an intracellular distribution, and VEGFR2 remained associated with the cell membrane. The altered localization pattern indicated reduced colocalization of the mutant protein with VEGFR2, suggesting a diminished ability of VEGFR2 binding. CONCLUSIONS: The study identified a novel missense variant (p.D239N) in DAB2IP in a family with HAE-UNK and highlighted the role of dysregulated VEGF-mediated signaling in altered endothelial permeability. DAB2IP loss-of-function pathogenic variants lead to the impairment of the endothelial VEGF/VEGFR2 ligand system and represent a new pathophysiologic cause of HAE-UNK.

CircFAM114A2 Suppresses Cell Proliferation, Migration, and Invasion of Colorectal Cancer Through Sponging miR-647 to Upregulate DAB2IP Expression.

BACKGROUND: Increasing evidence had proved that some circular RNA (circRNA) exerted critical roles in tumors progression by functioning as "microRNAs (miRNAs) sponges" to regulate their targeted genes. METHODS: circFAM114A2 and miR-647 expression was measured in CRC tissues and cells by quantitative real-time polymerase chain reaction (qRT-PCR), and the prognostic value of circFAM114A2 evaluated by Kaplan-Meier survival curve. Subsequently, wounding healing and transwell assays were performed to assess cell proliferation, migration, and invasion. RNA pull-down and dual-luciferase reporter assays were used to confirm the interactions between circFAM114A2, miR-647, and DAB2IP. RESULTS: CircFAM114A2 was notably downregulated in CRC tissues and cells, and low circFAM114A2 expression indicated the poor prognosis of CRC patients. Next, overexpression of circFAM114A2 suppressed CRC cells proliferation, migration, and invasion in vitro and impede CRC tumor growth in vivo. Mechanically, circFAM114A2 competitively bound to miR-647 and upregulated its target gene DAB2IP expression in CRC cells. CONCLUSION: Our results indicated that circFAM114A2/miR-647/DAP2IP axis played an important role in CRC progression, suggesting that circFAM114A2 might be a novel therapeutic target in patients with CRC.

DAB2IP stabilizes p27Kip1 via suppressing PI3K/AKT signaling in clear cell renal cell carcinoma.

Renal cell carcinoma (RCC) is the most lethal of the urologic malignancies. We previously discovered that DAB2IP, a novel Ras GTPase-activating protein, was frequently epigenetically silenced in RCC, and DAB2IP loss was correlated with the overall survival of RCC patients. In this study, we determined the biological functions of DAB2IP in clear cell RCC (ccRCC) and its potential mechanisms of action. Correlations between DAB2IP expression level and ccRCC tumor size and patient survival were analyzed, and the results showed that ccRCC patients with high DAB2IP mRNA level exhibited smaller tumor size and better survival than the patients with low DAB2IP. Compared to control, DAB2IP knockdown significantly increased cell proliferation, promoted cell cycle progression in G1/S phase, and decreased p27 expression. Mechanism studies demonstrated that loss of DAB2IP promoted p27 protein phosphorylation, cytosolic sequestration, and subsequently ubiquitination-mediated degradation in ccRCC cells. Further studies confirmed that the proline-rich domain in C terminal (CPR) of DAB2IP suppressed AKT phosphorylation and p27 phosphorylation on S10. Hence, DAB2IP is essential for p27 protein stabilization in ccRCC, which is at less partly mediated by PI3K/AKT signaling pathway.

Pumping the brakes on RAS - negative regulators and death effectors of RAS.

Mutations that activate the RAS oncoproteins are common in cancer. However, aberrant upregulation of RAS activity often occurs in the absence of activating mutations in the RAS genes due to defects in RAS regulators. It is now clear that loss of function of Ras GTPase-activating proteins (RasGAPs) is common in tumors, and germline mutations in certain RasGAP genes are responsible for some clinical syndromes. Although regulation of RAS is central to their activity, RasGAPs exhibit great diversity in their binding partners and therefore affect signaling by multiple mechanisms that are independent of RAS. The RASSF family of tumor suppressors are essential to RAS-induced apoptosis and senescence, and constitute a barrier to RAS-mediated transformation. Suppression of RASSF protein expression can also promote the development of excessive RAS signaling by uncoupling RAS from growth inhibitory pathways. Here, we will examine how these effectors of RAS contribute to tumor suppression, through both RAS-dependent and RAS-independent mechanisms.

DAB2IP predicts treatment response and prognosis of ESCC patients and modulates its radiosensitivity through enhancing IR-induced activation of the ASK1-JNK pathway.

BACKGROUND: Disabled homolog 2 interacting protein (DAB2IP) plays a tumor-suppressive role in several types of human cancers. However, the molecular status and function of the DAB2IP gene in esophageal squamous cell carcinoma (ESCC) patients who received definitive chemoradiotherapy is rarely reported. METHODS: We examined the expression dynamics of DAB2IP by immunohistochemistry (IHC) in 140 ESCC patients treated with definitive chemoradiotherapy. A series of in vivo and in vitro experiments were performed to elucidate the effect of DAB2IP on the chemoradiotherapy (CRT) response and its underlying mechanisms in ESCC. RESULTS: Decreased expression of DAB2IP in ESCCs correlated positively with ESCC resistance to CRT and was a strong and independent predictor for short disease-specific survival (DSS) of ESCC patients. Furthermore, the therapeutic sensitivity of CRT was substantially increased by ectopic overexpression of DAB2IP in ESCC cells. In addition, knockdown of DAB2IP dramatically enhanced resistance to CRT in ESCC. Finally, we demonstrated that DAB2IP regulates ESCC cell radiosensitivity through enhancing ionizing radiation (IR)-induced activation of the ASK1-JNK signaling pathway. CONCLUSIONS: Our data highlight the molecular etiology and clinical significance of DAB2IP in ESCC, which may represent a new therapeutic strategy to improve therapy and survival for ESCC patients.

DAB2IP down-regulates HSP90AA1 to inhibit the malignant biological behaviors of colorectal cancer.

BACKGROUND: Studies have shown that DAB2IP inhibits cancer progression, while HSP90AA1 promotes cancer progression. However, the specific regulatory mechanism of DAB2IP and HSP90AA1 in colorectal cancer (CRC) is not clear. Our aim is to investigate the role and mechanism of DAB2IP and HSP90AA1 in the development of CRC. METHODS: We used bioinformation to analyze the interaction between DAB2IP and HSP90AA1 and predict their downstream pathways. Then, a series of in vitro and in vivo experiments were conducted to reveal the role of DAB2IP and HSP90AA1 in the invasion and metastasis of colorectal cancer, and flow cytometry was used to explore their effects on apoptosis. RESULTS: Loss of DAB2IP was associated with poor prognosis of CRC. In contrast, elevated expression of HSP90AA1 was associated with the malignant behavior of CRC. The present study demonstrated a negative correlation between DAB2IP and HSP90AA1. Using bioinformatic analysis, we scanned SRP9 which was highly expressed in CRC, as a co-related gene of DAB2IP and HSP90AA1. Mechanistically, DAB2IP promoted apoptosis through HSP90AA1/SRP9/ASK1/JNK signaling axis in CRC. CONCLUSIONS: These findings provide evidence that DAB2IP-based therapy may enhance the anticancer effect of HSP90AA1 inhibitors, and combined targeting of DAB2IP and HSP90AA1 may be a powerful treatment strategy to combat CRC.

DOC-2/DAB2 interactive protein destabilizes c-Myc to impair the growth and self-renewal of colon tumor-repopulating cells.

Colorectal carcinoma (CRC) remains a huge challenge in clinical treatment due to tumor metastasis and recurrence. Stem cell-like colon tumor-repopulating cells (TRCs) are a subpopulation of cancer cells with highly tumorigenic and chemotherapy resistant properties. The core transcription factor c-Myc is essential for maintaining cancer stem-like cell phenotypes, yet its roles and regulatory mechanisms remain unclear in colon TRCs. We report that elevated c-Myc protein supported formation and growth of TRC spheroids. The tumor suppressor DOC-2/DAB2 interactive protein (DAB2IP) suppressed c-Myc expression to inhibit TRC expansion and self-renewal. Particularly, DAB2IP disrupted c-Myc stability through glycogen synthase kinase 3ß/protein phosphatase 2A-B56α-mediated phosphorylation and dephosphorylation cascade on c-Myc protein, leading to its eventual degradation through the ubiquitin-proteasome pathway. The expression of DAB2IP was negatively correlated with c-Myc in CRC specimens. Overall, our results improved mechanistic insight into how DAB2IP suppressed TRC growth and self-renewal.

Deletion of SMURF 1 represses ovarian cancer invasion and EMT by modulating the DAB2IP/AKT/Skp2 feedback loop.

SMAD ubiquitination regulatory factor 1 (SMURF1) has been described as a tumor suppressor in multiple aggressive cancers. Nevertheless, the potential role of SMURF1 in ovarian cancer invasion and epithelial-to-mesenchymal transition (EMT) remains unclear. The aim of this study was to evaluate the efficacy of SMURF1 on tumor migration and EMT and elucidate the underlying molecular mechanism in ovarian carcinoma. We found elevated SMURF1 in several ovarian cancer cells in both messenger RNA and protein. Additionally, silencing SMURF1 apparently repressed cell proliferation and invasion capacity of SKOV3 and A2780 cells and markedly attenuated expression of linked proteins such as proliferating cellnuclear antigen, matrix metalloproteinase (MMP)-2, and MMP-9. Furthermore, depletion of SMURF1 dramatically impeded EMT progress by modulating EMT biomarkers, with a notable increase in E-cadherin expression accompanied by the decrease in N-cadherin and vimentin in both SKOV3 and A2780 cells. Interestingly, elimination of SMURF1 led to disabled homolog 2 DOC-2/DAB2 interacting protein (DAB2IP) activation and dampened AKT/Skp2 signaling. Most important, depleted of DAB2IP or treatment with the AKT agonist 740Y-P effectively abolished the suppressive effects of SMURF1 knockout on cell invasiveness and EMT process. Taken all data together, these findings demonstrated that the absence of SMURF1 repressed cell proliferation, invasive capability, and EMT process in ovarian cancer through DAB2IP/AKT/Skp2 signaling loops, suggesting that SMURF1 may serve as a new potential therapeutic agent for ovarian cancer.

Down-regulation of DAB2IP promotes colorectal cancer invasion and metastasis by translocating hnRNPK into nucleus to enhance the transcription of MMP2.

DOC-2/DAB2 interacting protein (DAB2IP) is a RasGAP protein that shows a suppressive effect on cancer progression. Our previous study showed the involvement of transcription regulation of DAB2IP in metastasis of colorectal cancer (CRC). However, the molecular mechanisms of DAB2IP in regulating the progression of CRC need to be further explored. Here, we identified heterogeneous nuclear ribonucleoprotein K (hnRNPK) and matrix metalloproteinase 2 (MMP2) as vital downstream targets of DAB2IP in CRC cells by two-dimensional fluorescence difference gel electrophoresis and cDNA microassay, respectively. Mechanistically, down-regulation of DAB2IP increased the level of hnRNPK through MAPK/ERK signaling pathway. Subsequently, translocation of hnRNPK into nucleus enhanced the transcription activity of MMP2, and therefore promoted invasion and metastasis of CRC. Down-regulation of DAB2IP correlated negatively with hnRNPK and MMP2 expressions in CRC tissues. In conclusion, our study elucidates a novel mechanism of the DAB2IP/hnRNPK/MMP2 axis in the regulation of CRC invasion and metastasis, which may be a potential therapeutic target.

AIP1 mediates vascular endothelial cell growth factor receptor-3-dependent angiogenic and lymphangiogenic responses.

OBJECTIVE: To investigate the novel function of ASK1-interacting protein-1 (AIP1) in vascular endothelial cell growth factor receptor (VEGFR)-3 signaling, and VEGFR-3-dependent angiogenesis and lymphangiogenesis. APPROACH AND RESULTS: AIP1, a signaling scaffold protein, is highly expressed in the vascular endothelium. We have previously reported that AIP1 functions as an endogenous inhibitor in pathological angiogenesis by blocking VEGFR-2 activity. Surprisingly, here we observe that mice with a global deletion of AIP1-knockout mice (AIP1-KO) exhibit reduced retinal angiogenesis with less sprouting and fewer branches. Vascular endothelial cell (but not neuronal)-specific deletion of AIP1 causes similar defects in retinal angiogenesis. The reduced retinal angiogenesis correlates with reduced expression in VEGFR-3 despite increased VEGFR-2 levels in AIP1-KO retinas. Consistent with the reduced expression of VEGFR-3, AIP1-KO show delayed developmental lymphangiogenesis in neonatal skin and mesentery, and mount weaker VEGF-C-induced cornea lymphangiogenesis. In vitro, human lymphatic endothelial cells with AIP1 small interfering RNA knockdown, retinal endothelial cells, and lymphatic endothelial cells isolated from AIP1-KO all show attenuated VEGF-C-induced VEGFR-3 signaling. Mechanistically, we demonstrate that AIP1 via vegfr-3-specific miR-1236 increases VEGFR-3 protein expression and that, by directly binding to VEGFR-3, it enhances VEGFR-3 endocytosis and stability. CONCLUSION: Our in vivo and in vitro results provide the first insight into the mechanism by which AIP1 mediates VEGFR-3-dependent angiogenic and lymphangiogenic signaling.

Downregulation of DAB2IP results in cell proliferation and invasion and contributes to unfavorable outcomes in bladder cancer.

The DOC-2/DAB2 interactive protein (DAB2IP) is a member of the Ras GTPase-activating protein family. It has been shown to be often downregulated and a poor prognostic factor in several human malignancies. In this study, we analyzed the clinicopathological features and outcomes of DAB2IP expression in 135 patients with urothelial carcinoma of the bladder (UCB) treated by radical cystectomy plus bilateral lymph node dissection, and evaluated the effect of DAB2IP knockdown in vitro using the MTT method, colony formation assay, cell cycle assay, and cell migration and invasive assay. We found low expression of DAB2IP was significantly associated with high pathological stage (P = 0.002), high pathological grade (P = 0.02), tumor size more than 3 cm (P = 0.04), and presence of histological variants (P = 0.01). DAB2IP was an independent prognostic factor of disease recurrence (hazard ratio, 2.67; P = 0.034) and cancer-specific survival (hazard ratio, 2.79; P = 0.038). Knockdown of DAB2IP could promote cell proliferation, migration, and invasion. Downregulation of DAB2IP could activate the ERK and Akt pathways and was correlated with the expression of epithelial-mesenchymal transition markers, such as E-cadherin and vimentin. In conclusion, downregulation of DAB2IP is associated with features of biologically aggressive UCB and results in cell proliferation, migration, and invasion of bladder cancer. DAB2IP may serve as a promising biomarker in patients with UCB treated by radical cystectomy and bilateral lymph node dissection.

Dihydroartemisinin suppresses the tumorigenesis of esophageal carcinoma by elevating DAB2IP expression in a NFIC-dependent manner.

Dihydroartemisinin (DHA) has been identified to have the anticancer and anti-inflammatory activities. Disabled homolog 2 interacting protein (DAB2IP) is a well-recognized tumor suppressor. Both DHA and DAB2IP were proven to have suppressing effects on esophageal carcinoma (ESCA) tumorigenesis. However, whether DHA regulated ESCA cells via DAB2IP and its mechanism are still vague. Functional analyses were conducted using MTT, tube formation, sphere formation, and transwell assays in vitro as well as Tumor formation experiments in mice. Levels of genes and proteins were assayed by qRT-PCR and western blotting analyses. The interaction between DAB2IP and Nuclear Factor I C (NFIC) was confirmed using bioinformatics analysis and dual-luciferase reporter assay. DHA treatment suppressed ESCA cell angiogenesis, stemmess, migration, and invasion. DAB2IP level was decreased in ESCA tissues and cells, and DHA elevated DAB2IP expression in ESCA cells. Functionally, DAB2IP overexpression impaired ESCA cell angiogenesis, stemmess, migration and invasion. Mechanistically, NFIC had binding sites on the promoter region and directly targeted DAB2IP. DHA could up-regulate DAB2IP expression via NFIC. Moreover, NFIC was also decreased in ESCA tissues and cells, and its overexpression had anticancer activity in ESCA cells. In addition, DAB2IP knockdown reversed the anticancer effects of NFIC or DHA on ESCA cells. In further in vivo analysis, DHA also suppressed ESCA growth by regulating DAB2IP expression. DHA suppressed the tumorigenesis of ESCA by elevating DAB2IP expression in an NFIC-dependent manner, suggesting the potential clinical application of DHA in ESCA treatment.

Immunoexpression Patterns of Megalin, Cubilin, Caveolin-1, Gipc1 and Dab2IP in the Embryonic and Postnatal Development of the Kidneys in Yotari (Dab1-/-) Mice.

Our study examines the immunoexpression patterns of Megalin, Cubilin, Caveolin-1, Gipc1 and Dab2IP in the embryonic development (E) and postnatal (P) mouse kidney, with a focus on differentiating patterns between wild-type (wt) and yotari, Dab1-/- (yot) mice. Immunofluorescence revealed raised immunoexpression of receptors Megalin and Cubilin at the ampulla/collecting ducts and convoluted tubules across all developmental stages, with the most prominent immunoexpression observed in the convoluted tubules and the parietal epithelium of the Bowman's capsule. Quantitative analysis showed a higher percentage of Megalin and Cubilin in wt compared to yot mice at E13.5. Co-expression of Megalin and Cubilin was observed at the apical membrane of convoluted tubules and the parietal layer of the Bowman's capsule. The staining intensity of Megalin varied across developmental stages, with the strongest reactivity observed at the ampulla and collecting ducts at embryonic day (E) 13.5 in wt mice. In contrast, Caveolin-1 exhibited high immunoexpression in the metanephric mesenchyme, blood vessels, and the border area between the metanephric mesenchyme and renal vesicle, with a decrease in immunoexpression as development progressed. Gipc1 showed diffuse cytoplasmic staining in metanephric mesenchyme, convoluted tubules and collecting ducts, with significant differences in immunoexpression between wild-type and yot mice at both investigated embryonic time points. Dab2IP immunofluorescent staining was most prominent in renal vesicle/glomeruli and ampulla/collecting ducts at E13.5, with mild staining intensity observed in the distal convoluted tubules postnatally. Our findings elucidate distinct immunoexpression of patterns and potential parts of these proteins in the development and function of the kidney, highlighting the importance of further investigation into their regulatory mechanisms.

AIDA-1/ANKS1B Binds to the SynGAP Family RasGAPs with High Affinity and Specificity.

AIDA-1, encoded by ANKS1B, is an abundant postsynaptic scaffold protein essential for brain development. Mutations of ANKS1B are closely associated with various psychiatric disorders. However, very little is known regarding the molecular mechanisms underlying AIDA-1's involvements under physiological and pathophysiological conditions. Here, we discovered an interaction between AIDA-1 and the SynGAP family Ras-GTPase activating protein (GAP) via affinity purification using AIDA-1d as the bait. Biochemical studies showed that the PTB domain of AIDA-1 binds to an extended NPx[F/Y]-motif of the SynGAP family proteins with high affinities. The high-resolution crystal structure of AIDA-1 PTB domain in complex with the SynGAP NPxF-motif revealed the molecular mechanism governing the specific interaction between AIDA-1 and SynGAP. Our study not only explains why patients with ANKS1B or SYNGAP1 mutations share overlapping clinical phenotypes, but also allows identification of new AIDA-1 binding targets such as Ras and Rab interactors.

DAB2IP-knocking down resulted in radio-resistance of breast cancer cells is associated with increased hypoxia and vasculogenic mimicry formation.

PURPOSE: As a part of breast-conserving therapy (BCT), postoperative radiotherapy is one of the main means to improve the clinical efficacy of breast cancer (BCa). However, ionizing radiation (IR) may induce BCa cells to develop radioresistance, which causes tumor recurrence and metastasis after treatment. Recently, DOC-2/DAB2 interactive protein (DAB2IP) has been reported often down-regulated in a variety of cancers and is related to tumor tolerance to radiotherapy. In this study, BCa cell lines were introduced to study how DAB2IP deficient influenced BCa cell radiosensitivity in vitro and in vivo and discuss the possible mechanism. METHODS AND MATERIALS: Small RNA interference system (siRNA) was employed to decrease DAB2IP expression in two BCa cell lines, MDA-MB-231 and 4T1. Cells in response to IR or antineoplastics were detected by clone formation assay or MTT method, respectively. For in vivo studies, siDAB2IP or siControl cells were subcutaneously injected into the right flank of each female mouse. Sphere formation assay, soft agar colony anchoring assay and in vivo tumorigenesis assay were implemented to examine the stem cell-like features of BCa cells. Tube formation assay as well as immunofluorescence assay (IFA) were respectively applied to determine the angiogenesis of tumor cells in vitro and in vivo. The expression of a series of angiogenesis-related molecules was analyzed by qRT-PCR, western blot and IFA. RESULTS: It was observed that the downregulation of DAB2IP could significantly improve the clone formation ability of BCa cells, reduce their sensitivity to radiation and chemotherapy drugs, enhance their migration and invasion abilities and increase their stemness characteristics. It was also noted that either DAB2IP-knocking down or treated with the conditioned medium from DAB2IP-deficient BCa cells could promote the tube-forming ability of the endothelial cell. Similarly, in vivo studies showed that tumors developed from siDAB2IP BCa cells had higher tumor microvascular density (MVD) and more severe oxygen deficiency than that in DAB2IP- sufficient tumors. Meanwhile, Knock-down of DAB2IP inhibited vascular maturation and promoted the formation of vasculogenic mimicry (VM) in BCa tissues. Down-regulation of STAT3 could enhance siDAB2IP cells sensitivity to IR, accompanied by the decrease of VEGF expression. CONCLUSIONS: Our data support that loss of DAB2IP confers radio-resistance of BCa could be due to increased hypoxia, inhibited vascular maturation and promoted VM formation. STAT3 inhibition could be a potential way to overcome such DAB2IP-deficient induced tolerance in BCT.

circSLCO1B7 suppresses the malignant progression of hepatocellular carcinoma via the miR-556-3p/DAB2IP axis.

Circular RNAs (circRNAs) are noncoding RNAs with a circular colsed structure that play an important role in the occurrence and development of cancers. The functional mechanism of circRNAs as ceRNAs in hepatocellular carcinoma (HCC) and its effect on the invasion and metastasis of HCC need to be further studied. Five pairs of HCC tissues were selected for high-throughput sequencing, and 19 circRNAs with differential expression were obtained. The expression of circSLCO1B7 was obviously downregulated in 50 pairs of tumor tissues and plasma of HCC patients, which was closely related to the TNM stage, lymph node metastasis and tumor size. Cell functional experiments showed that circSLCO1B7 could inhibit cell growth, migration, invasion and promote cell apoptosis. In the regulatory mechanism, circSLCO1B7 sponged miR-556-3p to regulate the expression of the downstream target gene DAB2IP and induced the Epithelial-mesenchymal transition (EMT) progression. Our results indicated that circSLCO1B7 significantly inhibits the metastasis of HCC via the miR-556-3p/DAB2IP axis. Thus, circSLCO1B7 is a good candidate as a therapeutic target.

microRNA-1266-5p directly targets DAB2IP to enhance oncogenicity and metastasis in oral cancer.

Background/purpose: Oral cancer has been recognized as one of the most common malignancies worldwide and ranks the fifth leading cause of cancer death in Taiwan. A variety of studies have demonstrated that microRNAs are involved in the regulation of the hallmarks of oral carcinogenesis. Nevertheless, the effect of miR-1266-5p on the tumorigenesis of oral cancer has not been investigated, and not to mention, its functional role in oral cancer. Materials and methods: The upregulation of miR-1266-5p in SASVO3 and SASM5 cells was identified by RNA-Seq and examined by qRT-PCR analysis. The phenotypic assays including proliferation activity, migration capacity, invasion, wound healing, and colony-forming abilities were conducted in oral cancer cells after knockdown of miR-1266-5p. Luciferase reporter and western blotting were used to validate DAB2IP was a direct target of miR-1266-5p in oral cancer. Results: We identified that miR-1266-5p was significantly overexpressed in highly tumorigenic SASVO3 cells and metastatic SASM5 cells. qRT-PCR revealed that miR-1266 significantly increased upregulated in oral cancer and lymph node metastatic tissues compared to normal counterparts We found that downregulation of miR-1266-5p inhibited the proliferation and clonogenicity capacities of SASVO3 cells. Knockdown of miR-1266-5p also inhibited migration/invasion and self-renewal abilities in SASM5 cells. Moreover, we validated miR-1266-5p directly bound to the 3'UTR of DAB2IP in oral cancer cells. We found that DAB2IP knockdown reversed the inhibitory effects of self-renewal and migration mediated by silencing of miR-1266-5p. Conclusion: miR-1266 functions as a biomarker in oral cancer patients, and downregulation of miR-1266 may ameliorate the oncogenic and metastasis potential of oral cancer by targeting DAB2IP.

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.

DAB2IP attenuates chemoresistance of triple-negative breast cancer through sequestration of RAC1 to prevent ß-catenin nuclear accumulation.

BACKGROUND: Although chemotherapy, the most widely used systemic treatment in triple-negative breast cancer (TNBC), markedly improved the patients' outcome, chemoresistance always occurs. This study purposed to explore new therapeutic strategies for the treatment of chemoresistance. METHODS AND RESULTS: The expression and prognostic value of DAB2IP were investigated in TNBC tissues and cell lines. Low DAB2IP expression predicted high mortality risk in TNBC. Inhibition of DAB2IP expression conferred cancer stem cell capacity and chemoresistance in TNBC cell lines. Using murine breast cancer (BC) xenograft models, we evaluated the association with DAB2IP and chemoresistance. DAB2IP inhibited TNBC tumourigenesis and chemoresistance in vivo. Further, we revealed that DAB2IP inhibited ß-catenin nuclear transport through competitive interaction with RAC1 and decreased ß-catenin accumulation in the cell nucleus. Finally, we found that the DNA methylation level was negatively associated with DAB2IP expression in TNBC. Inhibition of DNA methylation restored the DAB2IP expression and attenuated chemoresistance in TNBC. CONCLUSIONS: We revealed that DAB2IP attenuates chemoresistance of TNBC via inhibition of RAC1-mediated ß-catenin nuclear accumulation. Decitabine treatment results in re-expression of DAB2IP by inhibiting DNA methylation and could be a potential therapeutic strategy for chemoresistance in TNBC.

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-1ß 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.