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PDK1-mTOR signaling pathway inhibitors reduce cell proliferation in MK2206 resistant neuroblastoma cells.

Qi L, Toyoda H, Xu DQ, Zhou Y, Sakurai N, Amano K, Kihira K, Hori H, Azuma E, Komada Y - Cancer Cell Int. (2015)

Bottom Line: GSK2334470 and AZD8055 effectively inhibited phosphorylation of PDK1 and mTOR, respectively, and induced higher G0-G1 ratio in LAN-1-MK than that in LAN-1 as well.PDK1 and mTOR inhibitors effected on phosphorylation of GSK3β in some of resistant sublines.Thus, suppression of PDK1-mTOR-S6K signaling pathway is an effective way to overcome the MK2206 resistance, and this may be a promising strategy for targeted therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics and Developmental Science, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie 514-8507 Japan ; Department of Pediatrics, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 1665 Kong Jiang Road, Shanghai, 200092 China.

ABSTRACT

Purpose: AKT plays a pivotal role in the signal transduction of cancer cells. MK2206, an AKT inhibitor, has been shown to be an effective anti-cancer drug to a variety of cancer cell lines. However, some cancer cells acquire resistance to MK2206 and new strategies to suppress these cell lines remain to be developed.

Experimental design: Acquired MK-2206-resistant neuroblastoma (NB) cell sublines were induced by stepwise escalation of MK-2206 exposure (4-12 weeks). MTT assay was used to validate cell proliferation. Flow cytometry was performed for cell cycle analysis. Western blot assay was used for cell signaling study.

Results: MK2206 (5-10 µmol) significantly suppressed cell growth of MK2206 non-resistant NB cells (LAN-1, KP-N-SIFA, NB-19 and SK-N-DZ), but is less efficient in inhibiting that of resistant sublines, even after 2-week MK2206-free incubation. MK2206 acted in mTOR-S6K dependent and independent methods. MK-2206 resistant sublines (LAN-1-MK, KP-N-SIFA-MK, and SK-N-DZ-MK) showed lower IC50 of GSK2334470 (PDK1 inhibitor). The cell growth of all sublines was prohibited by AZD8805 (mTOR inhibitor), with IC50 of AZD8805 3-10 times lower than MK2206 non-resistant cells. The signaling profiles of these resistant sublines were characterized by elevated PDK1-mTOR-S6K activity, accompanying by low phosphorylation of AKT compared with non-resistant counterparts. GSK2334470 and AZD8055 effectively inhibited phosphorylation of PDK1 and mTOR, respectively, and induced higher G0-G1 ratio in LAN-1-MK than that in LAN-1 as well. PDK1 and mTOR inhibitors effected on phosphorylation of GSK3β in some of resistant sublines.

Conclusion: NB cells can acquire MK2206 resistance after exposure for 4-12 weeks. Resistant cells feature reliance on PDK1-mTOR-S6K pathway and are more sensitive to PDK1 and mTOR inhibitors than the non-resistant counterparts. Thus, suppression of PDK1-mTOR-S6K signaling pathway is an effective way to overcome the MK2206 resistance, and this may be a promising strategy for targeted therapy.

No MeSH data available.


Related in: MedlinePlus

Schematic pathway alternations of MK-2206 resistance. a Signal pathway study of MK-2206 non-resistant cells showed that AKT acted in mTOR-S6K dependent method (LAN-1 and SK-N-DZ), in which inhibition of AKT reduced activity of mTOR-S6K signaling. Activity of PDK1 took the place of AKT, and elevated PDK1-mTOR-S6K transduction contributed to MK-2206 resistance, when AKT-mTOR-S6K was blocked. b AKT acted in mTOR-S6K independent method (KP-N-SIFA and NB-19), in which inhibition of AKT did not impair the activity of mTOR-S6K signaling. Parallel signaling pathway of PDK1-MTOR-S6K became an important alternative for cell growth of MK-2206-resistant sublines, when AKT was inhibited. And some other signal pathway may contribute to MK-2206 resistance as well
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Fig7: Schematic pathway alternations of MK-2206 resistance. a Signal pathway study of MK-2206 non-resistant cells showed that AKT acted in mTOR-S6K dependent method (LAN-1 and SK-N-DZ), in which inhibition of AKT reduced activity of mTOR-S6K signaling. Activity of PDK1 took the place of AKT, and elevated PDK1-mTOR-S6K transduction contributed to MK-2206 resistance, when AKT-mTOR-S6K was blocked. b AKT acted in mTOR-S6K independent method (KP-N-SIFA and NB-19), in which inhibition of AKT did not impair the activity of mTOR-S6K signaling. Parallel signaling pathway of PDK1-MTOR-S6K became an important alternative for cell growth of MK-2206-resistant sublines, when AKT was inhibited. And some other signal pathway may contribute to MK-2206 resistance as well

Mentions: In this study, MK-2206 showed inhibitory effect on cell growth of NB cell lines. Signal pathway study of MK-2206 non-resistant cells showed that AKT acted in mTOR-S6K dependent method (LAN-1 and SK-N-DZ), in which inhibition of AKT reduced activity of mTOR-S6K signaling; and mTOR-S6K independent method (KP-N-SIFA and NB-19), in which inhibition of AKT did not impair the activity of mTOR-S6K signaling. Step-wise exposure to MK-2206 induced acquired resistance in non-resistant cells. MK-2206-resistant sublines showed much lower IC50 of PDK1 and mTOR inhibitors, especially mTOR inhibitor (AZD8055). Signal pathway study of resistant sublines showed that LAN-1-MK and SK-N-DZ-MK expressed elevated PDK1-mTOR-S6K transduction (Fig. 7a), which indicated that activity of PDK1 took the place of AKT, and PDK1-mTOR-S6K signaling made contribution to cell growth of their resistant sublines. KP-N-SIFA-MK did not show amplification of mTOR-S6K signaling, but its elevated sensitivity to PDK1 and mTOR inhibitors implied that PDK1-mTOR-S6K transduction became an important alternative for cell growth of KP-N-SIFA-MK. Cell growth of NB-19-MK was related to MAPK pathway (Fig. 7b). Thus, continuous administration inducing signaling pathway alternation may offset MK-2206 inhibitory effect on cell growth, and MK-2206 resistance was not be overcome by short period interruption of administration (2 weeks). These observations suggest that NB cells may be able to enact mechanism base on signal transduction alternation to NB cell survive and escape cell death from singly MK-2206 exposure.Fig. 7


PDK1-mTOR signaling pathway inhibitors reduce cell proliferation in MK2206 resistant neuroblastoma cells.

Qi L, Toyoda H, Xu DQ, Zhou Y, Sakurai N, Amano K, Kihira K, Hori H, Azuma E, Komada Y - Cancer Cell Int. (2015)

Schematic pathway alternations of MK-2206 resistance. a Signal pathway study of MK-2206 non-resistant cells showed that AKT acted in mTOR-S6K dependent method (LAN-1 and SK-N-DZ), in which inhibition of AKT reduced activity of mTOR-S6K signaling. Activity of PDK1 took the place of AKT, and elevated PDK1-mTOR-S6K transduction contributed to MK-2206 resistance, when AKT-mTOR-S6K was blocked. b AKT acted in mTOR-S6K independent method (KP-N-SIFA and NB-19), in which inhibition of AKT did not impair the activity of mTOR-S6K signaling. Parallel signaling pathway of PDK1-MTOR-S6K became an important alternative for cell growth of MK-2206-resistant sublines, when AKT was inhibited. And some other signal pathway may contribute to MK-2206 resistance as well
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
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getmorefigures.php?uid=PMC4587771&req=5

Fig7: Schematic pathway alternations of MK-2206 resistance. a Signal pathway study of MK-2206 non-resistant cells showed that AKT acted in mTOR-S6K dependent method (LAN-1 and SK-N-DZ), in which inhibition of AKT reduced activity of mTOR-S6K signaling. Activity of PDK1 took the place of AKT, and elevated PDK1-mTOR-S6K transduction contributed to MK-2206 resistance, when AKT-mTOR-S6K was blocked. b AKT acted in mTOR-S6K independent method (KP-N-SIFA and NB-19), in which inhibition of AKT did not impair the activity of mTOR-S6K signaling. Parallel signaling pathway of PDK1-MTOR-S6K became an important alternative for cell growth of MK-2206-resistant sublines, when AKT was inhibited. And some other signal pathway may contribute to MK-2206 resistance as well
Mentions: In this study, MK-2206 showed inhibitory effect on cell growth of NB cell lines. Signal pathway study of MK-2206 non-resistant cells showed that AKT acted in mTOR-S6K dependent method (LAN-1 and SK-N-DZ), in which inhibition of AKT reduced activity of mTOR-S6K signaling; and mTOR-S6K independent method (KP-N-SIFA and NB-19), in which inhibition of AKT did not impair the activity of mTOR-S6K signaling. Step-wise exposure to MK-2206 induced acquired resistance in non-resistant cells. MK-2206-resistant sublines showed much lower IC50 of PDK1 and mTOR inhibitors, especially mTOR inhibitor (AZD8055). Signal pathway study of resistant sublines showed that LAN-1-MK and SK-N-DZ-MK expressed elevated PDK1-mTOR-S6K transduction (Fig. 7a), which indicated that activity of PDK1 took the place of AKT, and PDK1-mTOR-S6K signaling made contribution to cell growth of their resistant sublines. KP-N-SIFA-MK did not show amplification of mTOR-S6K signaling, but its elevated sensitivity to PDK1 and mTOR inhibitors implied that PDK1-mTOR-S6K transduction became an important alternative for cell growth of KP-N-SIFA-MK. Cell growth of NB-19-MK was related to MAPK pathway (Fig. 7b). Thus, continuous administration inducing signaling pathway alternation may offset MK-2206 inhibitory effect on cell growth, and MK-2206 resistance was not be overcome by short period interruption of administration (2 weeks). These observations suggest that NB cells may be able to enact mechanism base on signal transduction alternation to NB cell survive and escape cell death from singly MK-2206 exposure.Fig. 7

Bottom Line: GSK2334470 and AZD8055 effectively inhibited phosphorylation of PDK1 and mTOR, respectively, and induced higher G0-G1 ratio in LAN-1-MK than that in LAN-1 as well.PDK1 and mTOR inhibitors effected on phosphorylation of GSK3β in some of resistant sublines.Thus, suppression of PDK1-mTOR-S6K signaling pathway is an effective way to overcome the MK2206 resistance, and this may be a promising strategy for targeted therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics and Developmental Science, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie 514-8507 Japan ; Department of Pediatrics, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 1665 Kong Jiang Road, Shanghai, 200092 China.

ABSTRACT

Purpose: AKT plays a pivotal role in the signal transduction of cancer cells. MK2206, an AKT inhibitor, has been shown to be an effective anti-cancer drug to a variety of cancer cell lines. However, some cancer cells acquire resistance to MK2206 and new strategies to suppress these cell lines remain to be developed.

Experimental design: Acquired MK-2206-resistant neuroblastoma (NB) cell sublines were induced by stepwise escalation of MK-2206 exposure (4-12 weeks). MTT assay was used to validate cell proliferation. Flow cytometry was performed for cell cycle analysis. Western blot assay was used for cell signaling study.

Results: MK2206 (5-10 µmol) significantly suppressed cell growth of MK2206 non-resistant NB cells (LAN-1, KP-N-SIFA, NB-19 and SK-N-DZ), but is less efficient in inhibiting that of resistant sublines, even after 2-week MK2206-free incubation. MK2206 acted in mTOR-S6K dependent and independent methods. MK-2206 resistant sublines (LAN-1-MK, KP-N-SIFA-MK, and SK-N-DZ-MK) showed lower IC50 of GSK2334470 (PDK1 inhibitor). The cell growth of all sublines was prohibited by AZD8805 (mTOR inhibitor), with IC50 of AZD8805 3-10 times lower than MK2206 non-resistant cells. The signaling profiles of these resistant sublines were characterized by elevated PDK1-mTOR-S6K activity, accompanying by low phosphorylation of AKT compared with non-resistant counterparts. GSK2334470 and AZD8055 effectively inhibited phosphorylation of PDK1 and mTOR, respectively, and induced higher G0-G1 ratio in LAN-1-MK than that in LAN-1 as well. PDK1 and mTOR inhibitors effected on phosphorylation of GSK3β in some of resistant sublines.

Conclusion: NB cells can acquire MK2206 resistance after exposure for 4-12 weeks. Resistant cells feature reliance on PDK1-mTOR-S6K pathway and are more sensitive to PDK1 and mTOR inhibitors than the non-resistant counterparts. Thus, suppression of PDK1-mTOR-S6K signaling pathway is an effective way to overcome the MK2206 resistance, and this may be a promising strategy for targeted therapy.

No MeSH data available.


Related in: MedlinePlus