t-DARPP regulates phosphatidylinositol-3-kinase-dependent cell growth in breast cancer

Vangamudi, Bhavatarini; Peng, Dun Fa; Cai, Qiuyin; El–Rifai, Wael; Wang, Zheng; Belkhiri, Abbes

doi:10.1186/1476-4598-9-240

Cited by 42 publications

(66 citation statements)

References 31 publications

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“…5 μm of TMA sections were used for IHC staining of AXL receptor tyrosine kinase with polyclonal goat AXL antibody (1:200) (AF154; R&D Systems). The intensity and frequency of staining were graded as described previously (28). …”

Section: Methodsmentioning

confidence: 99%

ABL Regulation by AXL Promotes Cisplatin Resistance in Esophageal Cancer

et al. 2013

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Esophageal adenocarcinoma (EAC) is characterized by resistance to chemotherapy and poor outcome. Although Cisplatin (CDDP) has been used as a first-line therapy in patients with EAC, resistance remains a major clinical problem. The AXL receptor tyrosine kinase, originally isolated as a transforming gene from leukemia, is overexpressed in several solid tumors. Herein, we assessed AXL protein expression in human EACs and examined its role in CDDP resistance in human EAC cells. AXL overexpression was detected in >50% of tumors examined. Elevating AXL in non-overexpressing cells doubled the sensitivity to CDDP cytotoxicity and increased cell survival 3-fold, whereas attenuating AXL in ovexpressing cells reduced survival 2-fold. The effects of AXL modulation on cell survival associated with changes in cellular and molecular markers of apoptosis. Mechanistic investigations revealed that AXL blocked CDDP-induced activation of endogenous p73β (TP73), reducing its protein half-life, and inhibited CDDP-induced levels of p-c-ABL(Y412) and p-p73β(Y99). These changes were associated with a disruption of c-ABL/p73β protein interactions due to association with c-ABL in the cytoplasm, thereby blocking nuclear accumulation of c-ABL and phosphorylation of p73β in response to DNA damage. Together, our results establish that AXL promotes CDDP resistance in esophageal adenocarconima and argue that therapeutic targeting of AXL may sensitize these cancers to DNA damaging drugs.

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Section: Methodsmentioning

confidence: 99%

ABL Regulation by AXL Promotes Cisplatin Resistance in Esophageal Cancer

et al. 2013

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“…To measure cell proliferation, the Click-iT EdU Assay (Life Technologies) was performed following the manufacturer's recommendation, as previously described 15. EdU (5-ethynyl-2′-deoxyuridine) is a nucleoside analogue of thymidine and is incorporated into DNA during active DNA synthesis.…”

Section: Methodsmentioning

confidence: 99%

“…Western blot analysis was performed using standard protocols 15. The protein concentration was determined by a Bio-Rad protein assay using a FLUO Star OPTIMA microplate reader (BMG).…”

Section: Methodsmentioning

confidence: 99%

Glutathione peroxidase 7 has potential tumour suppressor functions that are silenced by location-specific methylation in oesophageal adenocarcinoma

Peng

Soutto

et al. 2013

Gut

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Objective We investigated the potential tumor suppressor functions of glutathione peroxidase 7 (GPX7) and examined the interplay between epigenetic and genetic events in regulating its expression in oesophageal adenocarcinomas (OAC). Design In vitro and in vivo cell models were developed to investigate the biological and molecular functions of GPX7 in OAC. RESULTS Reconstitution of GPX7 in OAC cell lines, OE33 and FLO-1, led to significant growth suppression as demonstrated by growth curve, colony formation and EdU proliferation assays. Meanwhile, GPX7-expressing cells displayed significant impairment in G1/S progression and an increase in cell senescence. Concordant with the above functions, Western blot analysis displayed higher levels of p73, p27, p21, and p16 with a decrease in phosphorylated RB; indicating its increased tumor suppressor activities. On the contrary, knockdown of GPX7 in HET1A cells (an immortalized normal esophageal cell line) rendered the cells growth advantage as indicated with a higher EdU rate, lower levels of p73, p27, p21, and p16 and an increase in phosphorylated RB. We confirmed the tumor suppressor function in vivo using GPX7-expressing OE33 cells in a mouse xenograft model. Pyrosequencing of the GPX7 promoter region (−162 to +138) demonstrated location-specific hypermethylation between +13 and +64 in OACs (69%, 54/78). This was significantly associated with the downregulation of GPX7 (p<0.01). Neither mutations in the coding exons of GPX7 nor DNA copy number losses were present in the OACs examined (<5%). CONCLUSIONS Our data suggest that GPX7 possesses tumor suppressor functions in OAC and is silenced by location-specific promoter DNA methylation.

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“…t-DARPP is overexpressed in several malignancies, such as those of the stomach, colon, breast, and prostate (13-15). We and others have shown that t-DARPP protein promotes cell growth, survival, and drug resistance through activation of AKT signaling in cancer cells (14, 16-18). …”

Section: Introductionmentioning

confidence: 93%

Regulation of ERBB2 Receptor by t-DARPP Mediates Trastuzumab Resistance in Human Esophageal Adenocarcinoma

Hong

Katsha

et al. 2012

Cancer Research

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Esophageal adenocarcinoma (EAC) is an aggressive malignancy with a poor outcome. Although targeting ERBB2 with trastuzumab is evaluated in clinical trials, the molecular mechanisms of trastuzumab resistance remain uncharacterized in EAC. The dopamine and cyclic AMP-regulated phosphoprotein of Mr 32,000 (DARPP-32), also known as PPP1R1B, is located together with ERBB2 at the 17q12-q21 amplicon. We evaluated the expression of a transcript variant of DARPP-32 (t-DARPP) and ERBB2 in 141 primary tumors and investigated the role of t-DARPP in trastuzumab resistance using OE19 and OE33 EAC cell models. Overexpression of t-DARPP mRNA was detected in two-thirds of tumors with a correlation between ERBB2 and t-DARPP overexpression levels (r=0.58, p=0.003). Cell viability and clonogenic survival assays showed that t-DARPP increased survival by 40% in response to trastuzumab (p<0.01). The Annexin-V staining and Western blot analysis indicated that t-DARPP effectively abrogated trastuzumab-induced apoptosis, inhibited cleavage of caspase-3 and blocked trastuzumab-induced dephosphorylation of ERBB2 and AKT proteins. The knockdown of endogenous t-DARPP reversed these effects and sensitized cells to trastuzumab (p<0.01). The cycloheximide-based protein degradation analysis indicated that t-DARPP extended the half-life of ERBB2 explaining the increase in the basal levels of ERBB2, p-ERBB2(Y1248), and p-AKT(S473). Coimmunoprecipitation and Western blot analysis demonstrated that t-DARPP associated with ERBB2 in a protein complex, and interfered with trastuzumab binding to the ERBB2 receptor. Using EAC-xenografted mouse model, t-DARPP enhanced tumor growth and rendered tumors unresponsive to trastuzumab. This study establishes t-DARPP as a mediator of trastuzumab resistance and underscores its potential importance in clinical trials of EAC.

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t-DARPP regulates phosphatidylinositol-3-kinase-dependent cell growth in breast cancer

Cited by 42 publications

References 31 publications

ABL Regulation by AXL Promotes Cisplatin Resistance in Esophageal Cancer

ABL Regulation by AXL Promotes Cisplatin Resistance in Esophageal Cancer

Glutathione peroxidase 7 has potential tumour suppressor functions that are silenced by location-specific methylation in oesophageal adenocarcinoma

Regulation of ERBB2 Receptor by t-DARPP Mediates Trastuzumab Resistance in Human Esophageal Adenocarcinoma

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