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NHE9 induces chemoradiotherapy resistance in esophageal squamous cell carcinoma by upregulating the Src/Akt/β-catenin pathway and Bcl-2 expression.

Chen J, Yang H, Wen J, Luo K, Liu Q, Huang Y, Zheng Y, Tan Z, Huang Q, Fu J - Oncotarget (2015)

Bottom Line: Our results showed that NHE9 prevented CRT-induced apoptosis.Importantly, we found that RACK1 is a novel binding partner of NHE9 and that NHE9-dependent induction of CRT resistance requires the activation of RACK1-associated Src/Akt/β-catenin signaling.Furthermore, combining either Dasatinib or ABT-737 with CRT significantly reduced tumor volume, and the response to CRT was restored when these inhibitors were used together with CRT in a xenograft nude mouse model with NHE9 overexpression.

View Article: PubMed Central - PubMed

Affiliation: Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China.

ABSTRACT
Recently, we found that NHE9 mRNA was upregulated in chemoradiotherapy (CRT)-resistant esophageal squamous cell carcinoma (ESCC); however, the underlying mechanisms were unclear. Here, we aimed to clarify the functional contribution of NHE9 to CRT resistance, understand the molecular basis of NHE9-dependent resistance in ESCC, and identify potential therapeutic targets. Our results showed that NHE9 prevented CRT-induced apoptosis. Importantly, we found that RACK1 is a novel binding partner of NHE9 and that NHE9-dependent induction of CRT resistance requires the activation of RACK1-associated Src/Akt/β-catenin signaling. Moreover, upregulated Bcl-2 protein was also observed in cells exhibiting NHE9-induced CRT resistance. A higher NHE9 level was associated with a poor response to CRT and less decrease in T and N stage in ESCC patients. Furthermore, combining either Dasatinib or ABT-737 with CRT significantly reduced tumor volume, and the response to CRT was restored when these inhibitors were used together with CRT in a xenograft nude mouse model with NHE9 overexpression. Taken together, our findings demonstrate that NHE9 can be an effective predictor of CRT response and may be useful in the development of targeted therapies for CRT-resistant ESCC.

No MeSH data available.


Related in: MedlinePlus

Interaction between NHE9 and RACK1A pull-down assay suggested that NHE9 has four potential binding partners A. A co-immunoprecipitation assay confirmed that RACK1 is a binding partner of NHE9 in ESCC cells B. The interaction of NHE9 and RACK1 was further confirmed by immunoprecipitation using anti-Flag C. or anti-Myc D. beads. All experiments were performed at least three times with the same results.
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Figure 4: Interaction between NHE9 and RACK1A pull-down assay suggested that NHE9 has four potential binding partners A. A co-immunoprecipitation assay confirmed that RACK1 is a binding partner of NHE9 in ESCC cells B. The interaction of NHE9 and RACK1 was further confirmed by immunoprecipitation using anti-Flag C. or anti-Myc D. beads. All experiments were performed at least three times with the same results.

Mentions: Although NHE9 can induce CRT resistance in ESCC by inhibiting cell apoptosis, the underlying mechanisms by which NHE9, an ion channel, affects apoptosis are unknown. NHE9 is known to contain binding sites in its intracellular C-terminus for many molecules; therefore, we hypothesized that NHE9 might play a role in apoptosis through its binding partners. A pull-down assay was performed using the C-terminus of NHE9 (generated via prokaryotic expression) fused to GST-Sepharose and Eca109 cell lysates. The protein complex was further analyzed by SELDI-TOF-MS, and 4 potential interacting proteins, including Homo sapiens glutathione S-transferase pi 1 (GSTP1), leucine-rich repeat and immunoglobulin-like domain-containing receptor-interacting protein 4 (LIGO4), polycystin-1 (PKD1), and receptor for activated C kinase 1 (RACK1) (Figure 4A), were identified.


NHE9 induces chemoradiotherapy resistance in esophageal squamous cell carcinoma by upregulating the Src/Akt/β-catenin pathway and Bcl-2 expression.

Chen J, Yang H, Wen J, Luo K, Liu Q, Huang Y, Zheng Y, Tan Z, Huang Q, Fu J - Oncotarget (2015)

Interaction between NHE9 and RACK1A pull-down assay suggested that NHE9 has four potential binding partners A. A co-immunoprecipitation assay confirmed that RACK1 is a binding partner of NHE9 in ESCC cells B. The interaction of NHE9 and RACK1 was further confirmed by immunoprecipitation using anti-Flag C. or anti-Myc D. beads. All experiments were performed at least three times with the same results.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4494947&req=5

Figure 4: Interaction between NHE9 and RACK1A pull-down assay suggested that NHE9 has four potential binding partners A. A co-immunoprecipitation assay confirmed that RACK1 is a binding partner of NHE9 in ESCC cells B. The interaction of NHE9 and RACK1 was further confirmed by immunoprecipitation using anti-Flag C. or anti-Myc D. beads. All experiments were performed at least three times with the same results.
Mentions: Although NHE9 can induce CRT resistance in ESCC by inhibiting cell apoptosis, the underlying mechanisms by which NHE9, an ion channel, affects apoptosis are unknown. NHE9 is known to contain binding sites in its intracellular C-terminus for many molecules; therefore, we hypothesized that NHE9 might play a role in apoptosis through its binding partners. A pull-down assay was performed using the C-terminus of NHE9 (generated via prokaryotic expression) fused to GST-Sepharose and Eca109 cell lysates. The protein complex was further analyzed by SELDI-TOF-MS, and 4 potential interacting proteins, including Homo sapiens glutathione S-transferase pi 1 (GSTP1), leucine-rich repeat and immunoglobulin-like domain-containing receptor-interacting protein 4 (LIGO4), polycystin-1 (PKD1), and receptor for activated C kinase 1 (RACK1) (Figure 4A), were identified.

Bottom Line: Our results showed that NHE9 prevented CRT-induced apoptosis.Importantly, we found that RACK1 is a novel binding partner of NHE9 and that NHE9-dependent induction of CRT resistance requires the activation of RACK1-associated Src/Akt/β-catenin signaling.Furthermore, combining either Dasatinib or ABT-737 with CRT significantly reduced tumor volume, and the response to CRT was restored when these inhibitors were used together with CRT in a xenograft nude mouse model with NHE9 overexpression.

View Article: PubMed Central - PubMed

Affiliation: Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China.

ABSTRACT
Recently, we found that NHE9 mRNA was upregulated in chemoradiotherapy (CRT)-resistant esophageal squamous cell carcinoma (ESCC); however, the underlying mechanisms were unclear. Here, we aimed to clarify the functional contribution of NHE9 to CRT resistance, understand the molecular basis of NHE9-dependent resistance in ESCC, and identify potential therapeutic targets. Our results showed that NHE9 prevented CRT-induced apoptosis. Importantly, we found that RACK1 is a novel binding partner of NHE9 and that NHE9-dependent induction of CRT resistance requires the activation of RACK1-associated Src/Akt/β-catenin signaling. Moreover, upregulated Bcl-2 protein was also observed in cells exhibiting NHE9-induced CRT resistance. A higher NHE9 level was associated with a poor response to CRT and less decrease in T and N stage in ESCC patients. Furthermore, combining either Dasatinib or ABT-737 with CRT significantly reduced tumor volume, and the response to CRT was restored when these inhibitors were used together with CRT in a xenograft nude mouse model with NHE9 overexpression. Taken together, our findings demonstrate that NHE9 can be an effective predictor of CRT response and may be useful in the development of targeted therapies for CRT-resistant ESCC.

No MeSH data available.


Related in: MedlinePlus