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Identification of a promising PI3K inhibitor for the treatment of multiple myeloma through the structural optimization.

Han K, Xu X, Chen G, Zeng Y, Zhu J, Du X, Zhang Z, Cao B, Liu Z, Mao X - J Hematol Oncol (2014)

Bottom Line: BENC-511 was able to inactivate PI3K and its downstream signals AKT, mTOR, p70S6K, and 4E-BP1 at 1 μM but had no effects on their total protein expression.Consistent with its effects on PI3K activity, BENC-511 induced MM cell apoptosis which was evidenced by the cleavage of Caspase-3 and PARP.Suppression of BENC-511 on MM tumor growth was associated with decreased PI3K/AKT activity and increased cell apoptosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Cyrus Tang Hematology Center, Soochow University, Suzhou, Jiangsu Province 215123, China. xinliangmao@suda.edu.cn.

ABSTRACT

Background: We previously reported a PI3K inhibitor S14161 which displays a promising preclinical activity against multiple myeloma (MM) and leukemia, but the chiral structure and poor solubility prevent its further application.

Methods: Six S14161 analogs were designed based on the structure-activity relationship; activity of the compounds in terms of cell death and inhibition of PI3K were analyzed by flow cytometry and Western blotting, respectively; anti-myeloma activity in vivo was performed on two independent xenograft models.

Results: Among the six analogs, BENC-511 was one of the most potent compounds which significantly inhibited PI3K activity and induced MM cell apoptosis. BENC-511 was able to inactivate PI3K and its downstream signals AKT, mTOR, p70S6K, and 4E-BP1 at 1 μM but had no effects on their total protein expression. Consistent with its effects on PI3K activity, BENC-511 induced MM cell apoptosis which was evidenced by the cleavage of Caspase-3 and PARP. Notably, addition of insulin-like growth factor 1 and interleukin-6, two important triggers for PI3K activation in MM cells, partly blocked BENC-511-induced MM cell death, which further demonstrated that PI3K signaling pathway was critical for the anti-myeloma activity of BENC-511. Moreover, BENC-511 also showed potent oral activity against myeloma in vivo. Oral administration of BENC-511 decreased tumor growth up to 80% within 3 weeks in two independent MM xenograft models at a dose of 50 mg/kg body weight, but presented minimal toxicity. Suppression of BENC-511 on MM tumor growth was associated with decreased PI3K/AKT activity and increased cell apoptosis.

Conclusions: Because of its potent anti-MM activity, low toxicity (LD50 oral >1.5 g/kg), and easy synthesis, BENC-511 could be developed as a promising agent for the treatment of MM via suppressing the PI3K/AKT signaling pathway.

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BENC-511 downregulates PI3K/AKT downstream signals. OPM2, RPMI-8226 and LP1 cells were treated with increasing concentrations of BENC-511 for 24 hours. Whole lysates were subjected to Western blot analysis. (A) p-mTOR (Ser2448), T-mTOR, Raptor; (B) p-p70S6K, p70S6K, p-4E-BP1, and 4E-BP1; (C) p-GSK-3β (Ser9). β-actin was used as an internal control.
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Figure 3: BENC-511 downregulates PI3K/AKT downstream signals. OPM2, RPMI-8226 and LP1 cells were treated with increasing concentrations of BENC-511 for 24 hours. Whole lysates were subjected to Western blot analysis. (A) p-mTOR (Ser2448), T-mTOR, Raptor; (B) p-p70S6K, p70S6K, p-4E-BP1, and 4E-BP1; (C) p-GSK-3β (Ser9). β-actin was used as an internal control.

Mentions: As a central node of various cell signals, PI3K/AKT can regulate many key important signals, including the mammalian target of rapamycin (mTOR), protein 70S6 kinase (p70S6K), factor 4E binding protein 1 (4E-BP1), and glycogen synthase kinase-3, all of these proteins are key players in regulating protein synthesis and cell proliferation [25,26]. To evaluate the biological effects of BENC-511 on the PI3K/AKT signaling pathway, we measured the effects of BENC-511 on these protein phosphorylation levels. MM cells were treated with BENC-511 for 24 hours at indicated concentrations. Immunoblotting assays with specific antibodies demonstrated that BENC-511 inhibited expression levels of phosphorylated mTOR as well as its adaptor protein Raptor (Figure 3A), phosphorylated p70S6K and 4E-BP1 (Figure 3B). BENC-511 also induced GSK-3β activation as seen in its phosphorylation level (Figure 3C). These changes, consistent with previous reports on PI3K inhibitors [27], further demonstrated that BENC-511 was an inhibitor of PI3K.


Identification of a promising PI3K inhibitor for the treatment of multiple myeloma through the structural optimization.

Han K, Xu X, Chen G, Zeng Y, Zhu J, Du X, Zhang Z, Cao B, Liu Z, Mao X - J Hematol Oncol (2014)

BENC-511 downregulates PI3K/AKT downstream signals. OPM2, RPMI-8226 and LP1 cells were treated with increasing concentrations of BENC-511 for 24 hours. Whole lysates were subjected to Western blot analysis. (A) p-mTOR (Ser2448), T-mTOR, Raptor; (B) p-p70S6K, p70S6K, p-4E-BP1, and 4E-BP1; (C) p-GSK-3β (Ser9). β-actin was used as an internal control.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3924225&req=5

Figure 3: BENC-511 downregulates PI3K/AKT downstream signals. OPM2, RPMI-8226 and LP1 cells were treated with increasing concentrations of BENC-511 for 24 hours. Whole lysates were subjected to Western blot analysis. (A) p-mTOR (Ser2448), T-mTOR, Raptor; (B) p-p70S6K, p70S6K, p-4E-BP1, and 4E-BP1; (C) p-GSK-3β (Ser9). β-actin was used as an internal control.
Mentions: As a central node of various cell signals, PI3K/AKT can regulate many key important signals, including the mammalian target of rapamycin (mTOR), protein 70S6 kinase (p70S6K), factor 4E binding protein 1 (4E-BP1), and glycogen synthase kinase-3, all of these proteins are key players in regulating protein synthesis and cell proliferation [25,26]. To evaluate the biological effects of BENC-511 on the PI3K/AKT signaling pathway, we measured the effects of BENC-511 on these protein phosphorylation levels. MM cells were treated with BENC-511 for 24 hours at indicated concentrations. Immunoblotting assays with specific antibodies demonstrated that BENC-511 inhibited expression levels of phosphorylated mTOR as well as its adaptor protein Raptor (Figure 3A), phosphorylated p70S6K and 4E-BP1 (Figure 3B). BENC-511 also induced GSK-3β activation as seen in its phosphorylation level (Figure 3C). These changes, consistent with previous reports on PI3K inhibitors [27], further demonstrated that BENC-511 was an inhibitor of PI3K.

Bottom Line: BENC-511 was able to inactivate PI3K and its downstream signals AKT, mTOR, p70S6K, and 4E-BP1 at 1 μM but had no effects on their total protein expression.Consistent with its effects on PI3K activity, BENC-511 induced MM cell apoptosis which was evidenced by the cleavage of Caspase-3 and PARP.Suppression of BENC-511 on MM tumor growth was associated with decreased PI3K/AKT activity and increased cell apoptosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Cyrus Tang Hematology Center, Soochow University, Suzhou, Jiangsu Province 215123, China. xinliangmao@suda.edu.cn.

ABSTRACT

Background: We previously reported a PI3K inhibitor S14161 which displays a promising preclinical activity against multiple myeloma (MM) and leukemia, but the chiral structure and poor solubility prevent its further application.

Methods: Six S14161 analogs were designed based on the structure-activity relationship; activity of the compounds in terms of cell death and inhibition of PI3K were analyzed by flow cytometry and Western blotting, respectively; anti-myeloma activity in vivo was performed on two independent xenograft models.

Results: Among the six analogs, BENC-511 was one of the most potent compounds which significantly inhibited PI3K activity and induced MM cell apoptosis. BENC-511 was able to inactivate PI3K and its downstream signals AKT, mTOR, p70S6K, and 4E-BP1 at 1 μM but had no effects on their total protein expression. Consistent with its effects on PI3K activity, BENC-511 induced MM cell apoptosis which was evidenced by the cleavage of Caspase-3 and PARP. Notably, addition of insulin-like growth factor 1 and interleukin-6, two important triggers for PI3K activation in MM cells, partly blocked BENC-511-induced MM cell death, which further demonstrated that PI3K signaling pathway was critical for the anti-myeloma activity of BENC-511. Moreover, BENC-511 also showed potent oral activity against myeloma in vivo. Oral administration of BENC-511 decreased tumor growth up to 80% within 3 weeks in two independent MM xenograft models at a dose of 50 mg/kg body weight, but presented minimal toxicity. Suppression of BENC-511 on MM tumor growth was associated with decreased PI3K/AKT activity and increased cell apoptosis.

Conclusions: Because of its potent anti-MM activity, low toxicity (LD50 oral >1.5 g/kg), and easy synthesis, BENC-511 could be developed as a promising agent for the treatment of MM via suppressing the PI3K/AKT signaling pathway.

Show MeSH
Related in: MedlinePlus