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Synthetic lethality by targeting EZH2 methyltransferase activity in ARID1A-mutated cancers.

Bitler BG, Aird KM, Garipov A, Li H, Amatangelo M, Kossenkov AV, Schultz DC, Liu Q, Shih IeM, Conejo-Garcia JR, Speicher DW, Zhang R - Nat. Med. (2015)

Bottom Line: Here we show that inhibition of the EZH2 methyltransferase acts in a synthetic lethal manner in ARID1A-mutated ovarian cancer cells and that ARID1A mutational status correlated with response to the EZH2 inhibitor.We identified PIK3IP1 as a direct target of ARID1A and EZH2 that is upregulated by EZH2 inhibition and contributed to the observed synthetic lethality by inhibiting PI3K-AKT signaling.To our knowledge, this is the first data set to demonstrate a synthetic lethality between ARID1A mutation and EZH2 inhibition.

View Article: PubMed Central - PubMed

Affiliation: Gene Expression and Regulation Program, The Wistar Institute, Philadelphia, Pennsylvania, USA.

ABSTRACT
The gene encoding ARID1A, a chromatin remodeler, shows one of the highest mutation rates across many cancer types. Notably, ARID1A is mutated in over 50% of ovarian clear cell carcinomas, which currently have no effective therapy. To date, clinically applicable targeted cancer therapy based on ARID1A mutational status has not been described. Here we show that inhibition of the EZH2 methyltransferase acts in a synthetic lethal manner in ARID1A-mutated ovarian cancer cells and that ARID1A mutational status correlated with response to the EZH2 inhibitor. We identified PIK3IP1 as a direct target of ARID1A and EZH2 that is upregulated by EZH2 inhibition and contributed to the observed synthetic lethality by inhibiting PI3K-AKT signaling. Importantly, EZH2 inhibition caused regression of ARID1A-mutated ovarian tumors in vivo. To our knowledge, this is the first data set to demonstrate a synthetic lethality between ARID1A mutation and EZH2 inhibition. Our data indicate that pharmacological inhibition of EZH2 represents a novel treatment strategy for cancers involving ARID1A mutations.

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EZH2 inhibitor causes the regression and reduces the number of tumor nodules of ARID1A mutated OCCC tumors. (a) 1×106 luciferase expressing ARID1A mutated OVISE cells were unilaterally injected into the bursa sac of the immuno-compromised female mice. The mice were randomized into two groups based on total luciferase flux for daily 50 mg/kg GSK126 or vehicle control treatments by intraperitoneal injection after 7 days. Mice were imaged every 7 days, and shown are images taken at day 14. (b) Quantification of tumor growth. n=5 and * P=0.0026. (c) At necropsy, the size of the dissected tumors was measured by subtracting control counter lateral ovary size from that of the size from the tumor cell injected one. n=5 and * P=0.003. (d) 3×106ARID1A mutated OVISE cells were injected into the intraperitoneal cavity of immuno-compromised female mice. Mice were randomly separated into two groups after 4 days for daily 50 mg/kg GSK126 or vehicle control treatments. On day 30, the number of tumor nodules in intraperitoneal cavity were assessed. n=6 and * P=0.008). (e) Immunohistochemical staining using the indicated antibodies for tumors dissected from GSK126 or control treated mice (magnification, 10X and 40X). Bars= 50 μm. (f) H-score quantification of (e). n=13 different fields from 5 different tumors. * P=0.0001; ** P=0.012 and # P=0.547. (g) A proposed model for the observed synthetic lethality between ARID1A mutation and inhibition of EZH2 methyltransferase activity. Error bars represent s.e.m. P calculated with two-tailed t test.
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Figure 6: EZH2 inhibitor causes the regression and reduces the number of tumor nodules of ARID1A mutated OCCC tumors. (a) 1×106 luciferase expressing ARID1A mutated OVISE cells were unilaterally injected into the bursa sac of the immuno-compromised female mice. The mice were randomized into two groups based on total luciferase flux for daily 50 mg/kg GSK126 or vehicle control treatments by intraperitoneal injection after 7 days. Mice were imaged every 7 days, and shown are images taken at day 14. (b) Quantification of tumor growth. n=5 and * P=0.0026. (c) At necropsy, the size of the dissected tumors was measured by subtracting control counter lateral ovary size from that of the size from the tumor cell injected one. n=5 and * P=0.003. (d) 3×106ARID1A mutated OVISE cells were injected into the intraperitoneal cavity of immuno-compromised female mice. Mice were randomly separated into two groups after 4 days for daily 50 mg/kg GSK126 or vehicle control treatments. On day 30, the number of tumor nodules in intraperitoneal cavity were assessed. n=6 and * P=0.008). (e) Immunohistochemical staining using the indicated antibodies for tumors dissected from GSK126 or control treated mice (magnification, 10X and 40X). Bars= 50 μm. (f) H-score quantification of (e). n=13 different fields from 5 different tumors. * P=0.0001; ** P=0.012 and # P=0.547. (g) A proposed model for the observed synthetic lethality between ARID1A mutation and inhibition of EZH2 methyltransferase activity. Error bars represent s.e.m. P calculated with two-tailed t test.

Mentions: GSK126 is a specific EZH2 inhibitor that is well tolerated in immunocompromised mice 9. We orthotopically injected luciferase-expressing ARID1A mutated OVISE cells into the immunocompromised female mouse bursa sac that covers the ovary. The injected cells were allowed to grow for one week to establish tumors. We randomly assigned mice into two groups (n=5/group) and treated mice daily with vehicle control or GSK126 (50 mg/kg) by intraperitoneal injection for an additional three weeks 9. GSK126 treatment caused regression of the orthotopically transplanted ARID1A mutated OVISE cells (Fig. 6a,b). At necropsy, we measured the orthotopically transplanted tumor size. GSK126 treatment significantly decreased the size of the orthotopically xenografted tumors compared with controls (Fig. 6c). Similarly, GSK126 treatment (50 mg/kg) caused regression of orthotopically xenografted ARID1A mutated TOV21G tumors after first establishing tumors for four weeks followed by two weeks of treatment (Supplementary Fig. 6a). In contrast, GSK126 treatment did not significantly affect the size of orthotopically xenografted ARID1A wild type RMG1 tumors (Supplementary Fig. 6b).


Synthetic lethality by targeting EZH2 methyltransferase activity in ARID1A-mutated cancers.

Bitler BG, Aird KM, Garipov A, Li H, Amatangelo M, Kossenkov AV, Schultz DC, Liu Q, Shih IeM, Conejo-Garcia JR, Speicher DW, Zhang R - Nat. Med. (2015)

EZH2 inhibitor causes the regression and reduces the number of tumor nodules of ARID1A mutated OCCC tumors. (a) 1×106 luciferase expressing ARID1A mutated OVISE cells were unilaterally injected into the bursa sac of the immuno-compromised female mice. The mice were randomized into two groups based on total luciferase flux for daily 50 mg/kg GSK126 or vehicle control treatments by intraperitoneal injection after 7 days. Mice were imaged every 7 days, and shown are images taken at day 14. (b) Quantification of tumor growth. n=5 and * P=0.0026. (c) At necropsy, the size of the dissected tumors was measured by subtracting control counter lateral ovary size from that of the size from the tumor cell injected one. n=5 and * P=0.003. (d) 3×106ARID1A mutated OVISE cells were injected into the intraperitoneal cavity of immuno-compromised female mice. Mice were randomly separated into two groups after 4 days for daily 50 mg/kg GSK126 or vehicle control treatments. On day 30, the number of tumor nodules in intraperitoneal cavity were assessed. n=6 and * P=0.008). (e) Immunohistochemical staining using the indicated antibodies for tumors dissected from GSK126 or control treated mice (magnification, 10X and 40X). Bars= 50 μm. (f) H-score quantification of (e). n=13 different fields from 5 different tumors. * P=0.0001; ** P=0.012 and # P=0.547. (g) A proposed model for the observed synthetic lethality between ARID1A mutation and inhibition of EZH2 methyltransferase activity. Error bars represent s.e.m. P calculated with two-tailed t test.
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Figure 6: EZH2 inhibitor causes the regression and reduces the number of tumor nodules of ARID1A mutated OCCC tumors. (a) 1×106 luciferase expressing ARID1A mutated OVISE cells were unilaterally injected into the bursa sac of the immuno-compromised female mice. The mice were randomized into two groups based on total luciferase flux for daily 50 mg/kg GSK126 or vehicle control treatments by intraperitoneal injection after 7 days. Mice were imaged every 7 days, and shown are images taken at day 14. (b) Quantification of tumor growth. n=5 and * P=0.0026. (c) At necropsy, the size of the dissected tumors was measured by subtracting control counter lateral ovary size from that of the size from the tumor cell injected one. n=5 and * P=0.003. (d) 3×106ARID1A mutated OVISE cells were injected into the intraperitoneal cavity of immuno-compromised female mice. Mice were randomly separated into two groups after 4 days for daily 50 mg/kg GSK126 or vehicle control treatments. On day 30, the number of tumor nodules in intraperitoneal cavity were assessed. n=6 and * P=0.008). (e) Immunohistochemical staining using the indicated antibodies for tumors dissected from GSK126 or control treated mice (magnification, 10X and 40X). Bars= 50 μm. (f) H-score quantification of (e). n=13 different fields from 5 different tumors. * P=0.0001; ** P=0.012 and # P=0.547. (g) A proposed model for the observed synthetic lethality between ARID1A mutation and inhibition of EZH2 methyltransferase activity. Error bars represent s.e.m. P calculated with two-tailed t test.
Mentions: GSK126 is a specific EZH2 inhibitor that is well tolerated in immunocompromised mice 9. We orthotopically injected luciferase-expressing ARID1A mutated OVISE cells into the immunocompromised female mouse bursa sac that covers the ovary. The injected cells were allowed to grow for one week to establish tumors. We randomly assigned mice into two groups (n=5/group) and treated mice daily with vehicle control or GSK126 (50 mg/kg) by intraperitoneal injection for an additional three weeks 9. GSK126 treatment caused regression of the orthotopically transplanted ARID1A mutated OVISE cells (Fig. 6a,b). At necropsy, we measured the orthotopically transplanted tumor size. GSK126 treatment significantly decreased the size of the orthotopically xenografted tumors compared with controls (Fig. 6c). Similarly, GSK126 treatment (50 mg/kg) caused regression of orthotopically xenografted ARID1A mutated TOV21G tumors after first establishing tumors for four weeks followed by two weeks of treatment (Supplementary Fig. 6a). In contrast, GSK126 treatment did not significantly affect the size of orthotopically xenografted ARID1A wild type RMG1 tumors (Supplementary Fig. 6b).

Bottom Line: Here we show that inhibition of the EZH2 methyltransferase acts in a synthetic lethal manner in ARID1A-mutated ovarian cancer cells and that ARID1A mutational status correlated with response to the EZH2 inhibitor.We identified PIK3IP1 as a direct target of ARID1A and EZH2 that is upregulated by EZH2 inhibition and contributed to the observed synthetic lethality by inhibiting PI3K-AKT signaling.To our knowledge, this is the first data set to demonstrate a synthetic lethality between ARID1A mutation and EZH2 inhibition.

View Article: PubMed Central - PubMed

Affiliation: Gene Expression and Regulation Program, The Wistar Institute, Philadelphia, Pennsylvania, USA.

ABSTRACT
The gene encoding ARID1A, a chromatin remodeler, shows one of the highest mutation rates across many cancer types. Notably, ARID1A is mutated in over 50% of ovarian clear cell carcinomas, which currently have no effective therapy. To date, clinically applicable targeted cancer therapy based on ARID1A mutational status has not been described. Here we show that inhibition of the EZH2 methyltransferase acts in a synthetic lethal manner in ARID1A-mutated ovarian cancer cells and that ARID1A mutational status correlated with response to the EZH2 inhibitor. We identified PIK3IP1 as a direct target of ARID1A and EZH2 that is upregulated by EZH2 inhibition and contributed to the observed synthetic lethality by inhibiting PI3K-AKT signaling. Importantly, EZH2 inhibition caused regression of ARID1A-mutated ovarian tumors in vivo. To our knowledge, this is the first data set to demonstrate a synthetic lethality between ARID1A mutation and EZH2 inhibition. Our data indicate that pharmacological inhibition of EZH2 represents a novel treatment strategy for cancers involving ARID1A mutations.

Show MeSH
Related in: MedlinePlus