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Integrin α6A splice variant regulates proliferation and the Wnt/β-catenin pathway in human colorectal cancer cells.

Groulx JF, Giroux V, Beauséjour M, Boudjadi S, Basora N, Carrier JC, Beaulieu JF - Carcinogenesis (2014)

Bottom Line: The α6A silencing was also found to be associated with a significant repression of a number of Wnt/β-catenin pathway end points.Moreover, it was accompanied by a reduction in the capacity of these cells to develop tumours in xenografts.Taken together, these results demonstrate that the α6A variant is a pro-proliferative form of the α6 integrin subunit in CRC cells and appears to mediate its effects through the Wnt/β-catenin pathway.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Intestinal Physiopathology, Department of Anatomy and Cell Biology and Department of Medicine, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada.

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Regulation of the Wnt/β-catenin pathway by the α6A variant subunit. Representative WB and graph of the densiometric analysis for the detection of active β-catenin and total β-catenin in the whole cell extract (A) and β-catenin in nuclear extracts (B). β-Actin served as loading control in cell extracts and histone H1 for nuclear extracts. Statistical analysis between shctrl and shα6A: *P ≤ 0.05, **P ≤ 0.01, t-test, n = 3. (C) TOPflash assay of the response of β-catenin/TCF4 promotor activity in the α6A variant knocked down cell lines and their corresponding shctrl. Results showed the net luciferase/renilla ratio (Topflash − FOPflash). Statistical analysis between shctrl and shα6A: *P ≤ 0.05, **P ≤ 0.01, t-test, n = 3.
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Figure 5: Regulation of the Wnt/β-catenin pathway by the α6A variant subunit. Representative WB and graph of the densiometric analysis for the detection of active β-catenin and total β-catenin in the whole cell extract (A) and β-catenin in nuclear extracts (B). β-Actin served as loading control in cell extracts and histone H1 for nuclear extracts. Statistical analysis between shctrl and shα6A: *P ≤ 0.05, **P ≤ 0.01, t-test, n = 3. (C) TOPflash assay of the response of β-catenin/TCF4 promotor activity in the α6A variant knocked down cell lines and their corresponding shctrl. Results showed the net luciferase/renilla ratio (Topflash − FOPflash). Statistical analysis between shctrl and shα6A: *P ≤ 0.05, **P ≤ 0.01, t-test, n = 3.

Mentions: The Wnt/β-catenin pathway is one of the most important regulators of cell proliferation in various systems and is often strongly deregulated in human CRC (35,36), thus suggesting a possible link between α6A expression and Wnt/β-catenin activity in CRC cells. Wnt/β-catenin activity was first evaluated by determining the level of GSK3β phosphorylation of β-catenin at ser37/thr41 using an active β-catenin antibody. WB analyses of whole cell lysates showed a statistically significant decrease in the levels of active β-catenin in all shα6A cell lines relative to total β-catenin compared with shctl cells (Figure 5A). This overall decrease was also reflected in WB analyses of nuclear extracts, where β-catenin was reduced in α6A knockdown Caco-2/15, DLD-1 and T84 (Figure 5B). These results suggest that in these CRC cells, depletion of the α6A integrin variant interferes with the Wnt/β-catenin pathway by enhancing the phosphorylation of β-catenin by GSK3β, targeting it to proteasome degradation and consequently reducing its accumulation in the nucleus.


Integrin α6A splice variant regulates proliferation and the Wnt/β-catenin pathway in human colorectal cancer cells.

Groulx JF, Giroux V, Beauséjour M, Boudjadi S, Basora N, Carrier JC, Beaulieu JF - Carcinogenesis (2014)

Regulation of the Wnt/β-catenin pathway by the α6A variant subunit. Representative WB and graph of the densiometric analysis for the detection of active β-catenin and total β-catenin in the whole cell extract (A) and β-catenin in nuclear extracts (B). β-Actin served as loading control in cell extracts and histone H1 for nuclear extracts. Statistical analysis between shctrl and shα6A: *P ≤ 0.05, **P ≤ 0.01, t-test, n = 3. (C) TOPflash assay of the response of β-catenin/TCF4 promotor activity in the α6A variant knocked down cell lines and their corresponding shctrl. Results showed the net luciferase/renilla ratio (Topflash − FOPflash). Statistical analysis between shctrl and shα6A: *P ≤ 0.05, **P ≤ 0.01, t-test, n = 3.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Show All Figures
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Figure 5: Regulation of the Wnt/β-catenin pathway by the α6A variant subunit. Representative WB and graph of the densiometric analysis for the detection of active β-catenin and total β-catenin in the whole cell extract (A) and β-catenin in nuclear extracts (B). β-Actin served as loading control in cell extracts and histone H1 for nuclear extracts. Statistical analysis between shctrl and shα6A: *P ≤ 0.05, **P ≤ 0.01, t-test, n = 3. (C) TOPflash assay of the response of β-catenin/TCF4 promotor activity in the α6A variant knocked down cell lines and their corresponding shctrl. Results showed the net luciferase/renilla ratio (Topflash − FOPflash). Statistical analysis between shctrl and shα6A: *P ≤ 0.05, **P ≤ 0.01, t-test, n = 3.
Mentions: The Wnt/β-catenin pathway is one of the most important regulators of cell proliferation in various systems and is often strongly deregulated in human CRC (35,36), thus suggesting a possible link between α6A expression and Wnt/β-catenin activity in CRC cells. Wnt/β-catenin activity was first evaluated by determining the level of GSK3β phosphorylation of β-catenin at ser37/thr41 using an active β-catenin antibody. WB analyses of whole cell lysates showed a statistically significant decrease in the levels of active β-catenin in all shα6A cell lines relative to total β-catenin compared with shctl cells (Figure 5A). This overall decrease was also reflected in WB analyses of nuclear extracts, where β-catenin was reduced in α6A knockdown Caco-2/15, DLD-1 and T84 (Figure 5B). These results suggest that in these CRC cells, depletion of the α6A integrin variant interferes with the Wnt/β-catenin pathway by enhancing the phosphorylation of β-catenin by GSK3β, targeting it to proteasome degradation and consequently reducing its accumulation in the nucleus.

Bottom Line: The α6A silencing was also found to be associated with a significant repression of a number of Wnt/β-catenin pathway end points.Moreover, it was accompanied by a reduction in the capacity of these cells to develop tumours in xenografts.Taken together, these results demonstrate that the α6A variant is a pro-proliferative form of the α6 integrin subunit in CRC cells and appears to mediate its effects through the Wnt/β-catenin pathway.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Intestinal Physiopathology, Department of Anatomy and Cell Biology and Department of Medicine, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada.

Show MeSH
Related in: MedlinePlus