Limits...
Loss of INPP4B causes a DNA repair defect through loss of BRCA1, ATM and ATR and can be targeted with PARP inhibitor treatment.

Ip LR, Poulogiannis G, Viciano FC, Sasaki J, Kofuji S, Spanswick VJ, Hochhauser D, Hartley JA, Sasaki T, Gewinner CA - Oncotarget (2015)

Bottom Line: The lipid phosphatase inositol polyphosphate 4-phosphatase type II (INPP4B) has been described as a tumor suppressor in the PI3K/Akt pathway with loss of expression found most pronounced in breast, ovarian cancer and melanoma.INPP4B loss resulted in significantly increased sensitivity towards PARP inhibition, comparable to loss of BRCA1 in two- and three-dimensional in vitro models, as well as in in vivo xenograft models.Loss of the tumor suppressor inositol polyphosphate 4-phosphatase type II (INPP4B) results in a DNA repair defect due to concomitant loss of BRCA1, ATR and ATM and can be therapeutically targeted with PARP inhibitors.

View Article: PubMed Central - PubMed

Affiliation: Department of Cancer Biology, UCL Cancer Institute, University College London, London, UK.

ABSTRACT
Treatment options for ovarian cancer patients remain limited and overall survival is less than 50% despite recent clinical advances. The lipid phosphatase inositol polyphosphate 4-phosphatase type II (INPP4B) has been described as a tumor suppressor in the PI3K/Akt pathway with loss of expression found most pronounced in breast, ovarian cancer and melanoma. Using microarray technology we identified a DNA repair defect in INPP4B-deficient cells, which we further characterized by comet assays and quantification of γH2AX, RAD51 and 53BP1 foci formation. INPP4B loss resulted in significantly increased sensitivity towards PARP inhibition, comparable to loss of BRCA1 in two- and three-dimensional in vitro models, as well as in in vivo xenograft models. Mechanistically, we discovered that INPP4B forms a protein complex with the key players of DNA repair, ATR and BRCA1, in GST pulldown and 293T overexpression assays, and INPP4B loss affects BRCA1, ATM and ATR protein stability resulting in the observed DNA repair defect. Given that INPP4B loss has been found in 40% of ovarian cancer patients, this study provides the rationale for establishing INPP4B as a biomarker of PARP inhibitor response, and consequently offers novel therapeutic options for a significant subset of patients. Loss of the tumor suppressor inositol polyphosphate 4-phosphatase type II (INPP4B) results in a DNA repair defect due to concomitant loss of BRCA1, ATR and ATM and can be therapeutically targeted with PARP inhibitors.

No MeSH data available.


Related in: MedlinePlus

INPP4B loss sensitizes to PARP inhibitor treatment in vitroA. Ovca429 Renilla luciferase, PTEN, INPP4B and BRCA1 knockdown pools were treated continuously with 1 μM Olaparib. Percentage clonogenic growth is displayed. B. Olaparib dose-response growth curve of human ovarian cell lines Ovca433 (INPP4B+/+, PTEN+/+), Ovcar-3 shRNA-Renilla luciferase (INPP4B−/−, PTEN+/+), Ovcar-3 shRNA-PTEN (INPP4B−/−, PTEN−/−) and A2780 (INPP4B−/−, PTEN−/−). (*p ≤ 0.05, **p ≤ = 0.01). C. Clonogenic assays of Ovca429 knockdown cell pools using cisplatin alone or in combination with continuous olaparib treatment. Percent inhibition clonogenic growth displayed. D. Olaparib dose response curve of Igrov-1 cells (INPP4B−/−, PTEN+/+) expressing Flag-INPP4B or empty vector control. Percent growth is displayed. E. In three-dimensional growth assays Ovca429 Renilla luciferase, PTEN or INPP4B knockdown cells were seeded and established spheroids treated with olaparib. Representative pictures are shown. F. Quantification of three-dimensional assay using a linear plot, G. or bar graphs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4496374&req=5

Figure 3: INPP4B loss sensitizes to PARP inhibitor treatment in vitroA. Ovca429 Renilla luciferase, PTEN, INPP4B and BRCA1 knockdown pools were treated continuously with 1 μM Olaparib. Percentage clonogenic growth is displayed. B. Olaparib dose-response growth curve of human ovarian cell lines Ovca433 (INPP4B+/+, PTEN+/+), Ovcar-3 shRNA-Renilla luciferase (INPP4B−/−, PTEN+/+), Ovcar-3 shRNA-PTEN (INPP4B−/−, PTEN−/−) and A2780 (INPP4B−/−, PTEN−/−). (*p ≤ 0.05, **p ≤ = 0.01). C. Clonogenic assays of Ovca429 knockdown cell pools using cisplatin alone or in combination with continuous olaparib treatment. Percent inhibition clonogenic growth displayed. D. Olaparib dose response curve of Igrov-1 cells (INPP4B−/−, PTEN+/+) expressing Flag-INPP4B or empty vector control. Percent growth is displayed. E. In three-dimensional growth assays Ovca429 Renilla luciferase, PTEN or INPP4B knockdown cells were seeded and established spheroids treated with olaparib. Representative pictures are shown. F. Quantification of three-dimensional assay using a linear plot, G. or bar graphs.

Mentions: As mutations in checkpoint and DNA repair pathways are associated with cancer, tumor cells defective in HR repair with diminished or ablated BRCA1/2 gene function, show extensive DNA repair lesions and are more sensitive to PARP inhibitors [26, 27]. We next determined whether lack of competent HR due to INPP4B loss might sensitize INPP4B-deficient human ovarian cancer cells to PARP inhibition. In clonogenic assays, upon continuous treatment with PARP inhibitor olaparib, Ovca429 and Ovca433 shRNA-INPP4B cell pools displayed significantly increased sensitivity similar to BRCA1 or PTEN knockdown (Ovca429, Figure 3A; Ovca433, Supplemental Figure 5A). In proliferation assays Ovca429 shRNA-INPP4B cell pools displayed a dose-dependent and significantly increased sensitivity upon olaparib treatment compared to controls (Supplemental Figure 5B).


Loss of INPP4B causes a DNA repair defect through loss of BRCA1, ATM and ATR and can be targeted with PARP inhibitor treatment.

Ip LR, Poulogiannis G, Viciano FC, Sasaki J, Kofuji S, Spanswick VJ, Hochhauser D, Hartley JA, Sasaki T, Gewinner CA - Oncotarget (2015)

INPP4B loss sensitizes to PARP inhibitor treatment in vitroA. Ovca429 Renilla luciferase, PTEN, INPP4B and BRCA1 knockdown pools were treated continuously with 1 μM Olaparib. Percentage clonogenic growth is displayed. B. Olaparib dose-response growth curve of human ovarian cell lines Ovca433 (INPP4B+/+, PTEN+/+), Ovcar-3 shRNA-Renilla luciferase (INPP4B−/−, PTEN+/+), Ovcar-3 shRNA-PTEN (INPP4B−/−, PTEN−/−) and A2780 (INPP4B−/−, PTEN−/−). (*p ≤ 0.05, **p ≤ = 0.01). C. Clonogenic assays of Ovca429 knockdown cell pools using cisplatin alone or in combination with continuous olaparib treatment. Percent inhibition clonogenic growth displayed. D. Olaparib dose response curve of Igrov-1 cells (INPP4B−/−, PTEN+/+) expressing Flag-INPP4B or empty vector control. Percent growth is displayed. E. In three-dimensional growth assays Ovca429 Renilla luciferase, PTEN or INPP4B knockdown cells were seeded and established spheroids treated with olaparib. Representative pictures are shown. F. Quantification of three-dimensional assay using a linear plot, G. or bar graphs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4496374&req=5

Figure 3: INPP4B loss sensitizes to PARP inhibitor treatment in vitroA. Ovca429 Renilla luciferase, PTEN, INPP4B and BRCA1 knockdown pools were treated continuously with 1 μM Olaparib. Percentage clonogenic growth is displayed. B. Olaparib dose-response growth curve of human ovarian cell lines Ovca433 (INPP4B+/+, PTEN+/+), Ovcar-3 shRNA-Renilla luciferase (INPP4B−/−, PTEN+/+), Ovcar-3 shRNA-PTEN (INPP4B−/−, PTEN−/−) and A2780 (INPP4B−/−, PTEN−/−). (*p ≤ 0.05, **p ≤ = 0.01). C. Clonogenic assays of Ovca429 knockdown cell pools using cisplatin alone or in combination with continuous olaparib treatment. Percent inhibition clonogenic growth displayed. D. Olaparib dose response curve of Igrov-1 cells (INPP4B−/−, PTEN+/+) expressing Flag-INPP4B or empty vector control. Percent growth is displayed. E. In three-dimensional growth assays Ovca429 Renilla luciferase, PTEN or INPP4B knockdown cells were seeded and established spheroids treated with olaparib. Representative pictures are shown. F. Quantification of three-dimensional assay using a linear plot, G. or bar graphs.
Mentions: As mutations in checkpoint and DNA repair pathways are associated with cancer, tumor cells defective in HR repair with diminished or ablated BRCA1/2 gene function, show extensive DNA repair lesions and are more sensitive to PARP inhibitors [26, 27]. We next determined whether lack of competent HR due to INPP4B loss might sensitize INPP4B-deficient human ovarian cancer cells to PARP inhibition. In clonogenic assays, upon continuous treatment with PARP inhibitor olaparib, Ovca429 and Ovca433 shRNA-INPP4B cell pools displayed significantly increased sensitivity similar to BRCA1 or PTEN knockdown (Ovca429, Figure 3A; Ovca433, Supplemental Figure 5A). In proliferation assays Ovca429 shRNA-INPP4B cell pools displayed a dose-dependent and significantly increased sensitivity upon olaparib treatment compared to controls (Supplemental Figure 5B).

Bottom Line: The lipid phosphatase inositol polyphosphate 4-phosphatase type II (INPP4B) has been described as a tumor suppressor in the PI3K/Akt pathway with loss of expression found most pronounced in breast, ovarian cancer and melanoma.INPP4B loss resulted in significantly increased sensitivity towards PARP inhibition, comparable to loss of BRCA1 in two- and three-dimensional in vitro models, as well as in in vivo xenograft models.Loss of the tumor suppressor inositol polyphosphate 4-phosphatase type II (INPP4B) results in a DNA repair defect due to concomitant loss of BRCA1, ATR and ATM and can be therapeutically targeted with PARP inhibitors.

View Article: PubMed Central - PubMed

Affiliation: Department of Cancer Biology, UCL Cancer Institute, University College London, London, UK.

ABSTRACT
Treatment options for ovarian cancer patients remain limited and overall survival is less than 50% despite recent clinical advances. The lipid phosphatase inositol polyphosphate 4-phosphatase type II (INPP4B) has been described as a tumor suppressor in the PI3K/Akt pathway with loss of expression found most pronounced in breast, ovarian cancer and melanoma. Using microarray technology we identified a DNA repair defect in INPP4B-deficient cells, which we further characterized by comet assays and quantification of γH2AX, RAD51 and 53BP1 foci formation. INPP4B loss resulted in significantly increased sensitivity towards PARP inhibition, comparable to loss of BRCA1 in two- and three-dimensional in vitro models, as well as in in vivo xenograft models. Mechanistically, we discovered that INPP4B forms a protein complex with the key players of DNA repair, ATR and BRCA1, in GST pulldown and 293T overexpression assays, and INPP4B loss affects BRCA1, ATM and ATR protein stability resulting in the observed DNA repair defect. Given that INPP4B loss has been found in 40% of ovarian cancer patients, this study provides the rationale for establishing INPP4B as a biomarker of PARP inhibitor response, and consequently offers novel therapeutic options for a significant subset of patients. Loss of the tumor suppressor inositol polyphosphate 4-phosphatase type II (INPP4B) results in a DNA repair defect due to concomitant loss of BRCA1, ATR and ATM and can be therapeutically targeted with PARP inhibitors.

No MeSH data available.


Related in: MedlinePlus