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Cbl-b inhibits P-gp transporter function by preventing its translocation into caveolae in multiple drug-resistant gastric and breast cancers.

Zhang Y, Qu X, Teng Y, Li Z, Xu L, Liu J, Ma Y, Fan Y, Li C, Liu S, Wang Z, Hu X, Zhang J, Liu Y - Oncotarget (2015)

Bottom Line: The transport function of P-glycoprotein (P-gp) requires its efficient localization to caveolae, a subset of lipid rafts, and disruption of caveolae suppresses P-gp transport function.However, the regulatory molecules involved in the translocation of P-gp into caveolae remain unknown.In a negative feedback loop, the translocation of Cbl-b from the nucleus to the cytoplasm prevented the localization of P-gp to caveolae resulting in the reversal of MDR through the ubiquitination and degradation of c-Src.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Oncology, the First Hospital of China Medical University, Shenyang 110001, China.

ABSTRACT
The transport function of P-glycoprotein (P-gp) requires its efficient localization to caveolae, a subset of lipid rafts, and disruption of caveolae suppresses P-gp transport function. However, the regulatory molecules involved in the translocation of P-gp into caveolae remain unknown. In the present study, we showed that c-Src dependent Caveolin-1 phosphorylation promoted the translocation of P-gp into caveolae, resulting in multidrug resistance in adriamycin resistant gastric cancer SGC7901/Adr and breast cancer MCF-7/Adr cells. In a negative feedback loop, the translocation of Cbl-b from the nucleus to the cytoplasm prevented the localization of P-gp to caveolae resulting in the reversal of MDR through the ubiquitination and degradation of c-Src. Clinical data showed a significant positive relationship between Cbl-b expression and survival in P-gp positive breast cancer patients who received anthracycline-based chemotherapy. Our findings identified a new regulatory mechanism of P-gp transport function in multiple drug-resistant gastric and breast cancers.

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Dox induced the translocation of Cbl-b from the nucleus to the cytoplasm(A) Western blot analysis of cytoplasmic and nuclear fractions from SGC7901 and SGC7901/Adr cells. Nuclear fractionation was confirmed by detection of total histone. Cytoplasmic fractionation was confirmed by detection of actin. (B) Immunofluorescence microscopy analysis of cytoplasmic and nuclear Cbl-b expression. (C) Western blot analysis of cytoplasmic and nuclear fractions from SGC7901/Adr cells treated with 20 μg/ml Dox for 1, 5, and 30 min. Nuclear fractionation was confirmed by detection of total histone and cytoplasmic fractionation by actin.
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Figure 4: Dox induced the translocation of Cbl-b from the nucleus to the cytoplasm(A) Western blot analysis of cytoplasmic and nuclear fractions from SGC7901 and SGC7901/Adr cells. Nuclear fractionation was confirmed by detection of total histone. Cytoplasmic fractionation was confirmed by detection of actin. (B) Immunofluorescence microscopy analysis of cytoplasmic and nuclear Cbl-b expression. (C) Western blot analysis of cytoplasmic and nuclear fractions from SGC7901/Adr cells treated with 20 μg/ml Dox for 1, 5, and 30 min. Nuclear fractionation was confirmed by detection of total histone and cytoplasmic fractionation by actin.

Mentions: The localization of Cbl-b in P-gp positive and negative cells was analyzed by western blotting (Figure 4A). In SGC7901/Adr cells, Cbl-b was mainly detected in the nucleus, whereas in parental SGC7901 cells, it was mostly detected in the cytoplasm (Figure 4B). Western blotting also showed that Dox (20 μg/ml) rapidly triggered Cbl-b translocation from the nucleus to cytoplasm in a time-dependent manner (Figure 4C). Low dose Dox (2 μg/ml) could not trigger Cbl-b translocation from the nucleus to the cytoplasm (Supplementary Figure 3, available online).


Cbl-b inhibits P-gp transporter function by preventing its translocation into caveolae in multiple drug-resistant gastric and breast cancers.

Zhang Y, Qu X, Teng Y, Li Z, Xu L, Liu J, Ma Y, Fan Y, Li C, Liu S, Wang Z, Hu X, Zhang J, Liu Y - Oncotarget (2015)

Dox induced the translocation of Cbl-b from the nucleus to the cytoplasm(A) Western blot analysis of cytoplasmic and nuclear fractions from SGC7901 and SGC7901/Adr cells. Nuclear fractionation was confirmed by detection of total histone. Cytoplasmic fractionation was confirmed by detection of actin. (B) Immunofluorescence microscopy analysis of cytoplasmic and nuclear Cbl-b expression. (C) Western blot analysis of cytoplasmic and nuclear fractions from SGC7901/Adr cells treated with 20 μg/ml Dox for 1, 5, and 30 min. Nuclear fractionation was confirmed by detection of total histone and cytoplasmic fractionation by actin.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4466646&req=5

Figure 4: Dox induced the translocation of Cbl-b from the nucleus to the cytoplasm(A) Western blot analysis of cytoplasmic and nuclear fractions from SGC7901 and SGC7901/Adr cells. Nuclear fractionation was confirmed by detection of total histone. Cytoplasmic fractionation was confirmed by detection of actin. (B) Immunofluorescence microscopy analysis of cytoplasmic and nuclear Cbl-b expression. (C) Western blot analysis of cytoplasmic and nuclear fractions from SGC7901/Adr cells treated with 20 μg/ml Dox for 1, 5, and 30 min. Nuclear fractionation was confirmed by detection of total histone and cytoplasmic fractionation by actin.
Mentions: The localization of Cbl-b in P-gp positive and negative cells was analyzed by western blotting (Figure 4A). In SGC7901/Adr cells, Cbl-b was mainly detected in the nucleus, whereas in parental SGC7901 cells, it was mostly detected in the cytoplasm (Figure 4B). Western blotting also showed that Dox (20 μg/ml) rapidly triggered Cbl-b translocation from the nucleus to cytoplasm in a time-dependent manner (Figure 4C). Low dose Dox (2 μg/ml) could not trigger Cbl-b translocation from the nucleus to the cytoplasm (Supplementary Figure 3, available online).

Bottom Line: The transport function of P-glycoprotein (P-gp) requires its efficient localization to caveolae, a subset of lipid rafts, and disruption of caveolae suppresses P-gp transport function.However, the regulatory molecules involved in the translocation of P-gp into caveolae remain unknown.In a negative feedback loop, the translocation of Cbl-b from the nucleus to the cytoplasm prevented the localization of P-gp to caveolae resulting in the reversal of MDR through the ubiquitination and degradation of c-Src.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Oncology, the First Hospital of China Medical University, Shenyang 110001, China.

ABSTRACT
The transport function of P-glycoprotein (P-gp) requires its efficient localization to caveolae, a subset of lipid rafts, and disruption of caveolae suppresses P-gp transport function. However, the regulatory molecules involved in the translocation of P-gp into caveolae remain unknown. In the present study, we showed that c-Src dependent Caveolin-1 phosphorylation promoted the translocation of P-gp into caveolae, resulting in multidrug resistance in adriamycin resistant gastric cancer SGC7901/Adr and breast cancer MCF-7/Adr cells. In a negative feedback loop, the translocation of Cbl-b from the nucleus to the cytoplasm prevented the localization of P-gp to caveolae resulting in the reversal of MDR through the ubiquitination and degradation of c-Src. Clinical data showed a significant positive relationship between Cbl-b expression and survival in P-gp positive breast cancer patients who received anthracycline-based chemotherapy. Our findings identified a new regulatory mechanism of P-gp transport function in multiple drug-resistant gastric and breast cancers.

Show MeSH
Related in: MedlinePlus