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Inhibition of AKT signalling by benzoxazine derivative LTUR6 through the modulation of downstream kinases


Many compounds structurally similar to chromones have been developed to enhance the sensitizing effect of cancer cells to chemotherapeutic agents. Most of these compounds have been shown to promote this sensitization by targeting the repair pathways. One such compound is LTUR6, which enhances the sensitization of doxorubicin to colon cancer cells HT29, by inhibiting the phosphorylation of the double stranded break (DSB) repair enzyme AKT. The downstream regulatory targets of AKT that enhance doxorubicin mediated cytotoxicity in the presence of LTUR6 remains elusive. In this study, we performed comparative analyses of 43 kinase phosphorylation sites using the human phospho-kinase array proteome profiler. Results revealed altered expression levels of multiple proteins that regulated apoptotic signalling pathways. Increased activation of mTOR, RSK1/2/3, p38α and PRAS40 after combination treatment with LTUR6 and doxorubicin over doxorubicin alone was observed. This study provides a deeper insight into the key proteins involved and presents a novel molecular pathway.

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Fig. 1: Key proteins identified in regulating apoptotic pathway downstream to AKT.
Fig. 2: Proposed mechanism of action LTUR6.


  1. Cantley LC (2002) The phosphoinositide 3-kinase pathway. Science 296(5573):1655–1657.

  2. Fruman DA, Meyers RE, Cantley LC (1998) Phosphoinositide kinases. Annu Rev Biochem.

  3. Vivanco I, Sawyers CL (2002) The phosphatidylinositol 3-kinase-AKT pathway in humancancer. Nat Rev Cancer 2:489–501.

    Article  PubMed  CAS  Google Scholar 

  4. Katso R, Okkenhaug K, Ahmadi K, White S, Timms J, Waterfield MD (2001) Cellular function of phosphoinositide 3-kinases: implications for development, immunity, homeostasis, and cancer. Annu Rev Cell Dev Biol 17:615–675.

    Article  PubMed  CAS  Google Scholar 

  5. Akinleye A, Chen Y, Mukhi N, Song Y, Liu D (2013) Ibrutinib and novel BTK inhibitors in clinical development. J Hematol Oncol 6:59

    Article  PubMed  CAS  PubMed Central  Google Scholar 

  6. Burris HA (2013) Overcoming acquired resistance to anticancer therapy: focus on the PI3K/AKT/mTOR pathway. Cancer Chemother Pharmacol 71:829–842

    Article  PubMed  CAS  Google Scholar 

  7. Workman P, Clarke PA, Raynaud FI, RLM VM (2010) Drugging the PI3 kinome: from chemical tools to drugs in the clinic. Cancer Res 70:2146–2157

    Article  PubMed  CAS  PubMed Central  Google Scholar 

  8. Sarbassov DD, Guertin DA, Ali SM, Sabatini DM (2005) Phosphorylation and regulation of Akt/PKB by the rictor-mTOR complex. Science 307(5712):1098–1101.

  9. Morrison R, Al-Rawi JMA (2016) Synthesis, structure elucidation, DNA-PK, PI3K, anti-platelet and anti-bacteria activity of linear 5, 6, and 10-substituted-2-morpholino-chromen-oxazine-dione and angular 3, 4, 6-substituted-8-morpholino-chromen-oxazine-2,10-dione. J Enzyme Inhib Med Chem 31:86–95.

    Article  PubMed  CAS  Google Scholar 

  10. Suraj R, Radhamani S, Meehan-Andrews T, Bradley C (2017) Role of a novel benzoxazine derivative in the chemosensitization of colon cancer. Apoptosis 22:988–1000.

    Article  PubMed  CAS  Google Scholar 

  11. Anjum R, Blenis J (2008) The RSK family of kinases: emerging roles in cellular signalling. Nat Rev Mol Cell Biol 9:747–758

    Article  PubMed  CAS  Google Scholar 

  12. Frödin M, Gammeltoft S (1999) Role and regulation of 90 kDa ribosomal S6 kinase (RSK) in signal transduction. Mol Cell Endocrinol 151:65–77

    Article  PubMed  Google Scholar 

  13. Neise D, Sohn D, Stefanski A et al (2013) The p90 ribosomal S6 kinase (RSK) inhibitor BI-D1870 prevents gamma irradiation-induced apoptosis and mediates senescence via RSK- and p53-independent accumulation of p21WAF1/CIP1. Cell Death Dis 4:e859.

    Article  PubMed  CAS  PubMed Central  Google Scholar 

  14. Carriere A (2008) The RSK factors of activating the Ras/MAPK signaling cascade. Front Biosci Volume:4258.

    Article  Google Scholar 

  15. Hay N, Sonenberg N (2004) Upstream and downstream of mTOR. Genes Dev 18:1926–1945

    Article  PubMed  CAS  Google Scholar 

  16. Yang H, Rudge DG, Koos JD, Vaidialingam B, Yang HJ, Pavletich NP (2013) MTOR kinase structure, mechanism and regulation. Nature 497:217–223.

    Article  PubMed  CAS  PubMed Central  Google Scholar 

  17. Park S, Chapuis N, Tamburini J, Bardet V, Cornillet-Lefebvre P, Willems L, Green A, Mayeux P, Lacombe C, Bouscary D (2010) Role of the PI3K/AKT and mTOR signaling pathways in acute myeloid leukemia. Haematologica 95:819–828.

    Article  PubMed  CAS  Google Scholar 

  18. Martelli AA, Evangelisti C, Chiarini F, McCubrey JA (2010) The phosphatidylinositol 3-kinase/AKT/mTOR signaling network as a therapeutic target in acute myelogenous leukemia patients. Oncotarget 1:89–103.

    Article  PubMed  PubMed Central  Google Scholar 

  19. Thedieck K, Polak P, Kim ML, Molle KD, Cohen A, Jenö P, Arrieumerlou C, Hall MN (2007) PRAS40 and PRR5-like protein are new mTOR interactors that regulate apoptosis. PLoS One 2:e1217.

    Article  PubMed  CAS  PubMed Central  Google Scholar 

  20. Laplante M, Sabatini DM (2012) mTOR signaling in growth control and disease. Cell 149:274–293.

  21. Han EKH, Leverson JD, McGonigal T, Shah OJ, Woods KW, Hunter T, Giranda VL, Luo Y (2007) Akt inhibitor A-443654 induces rapid Akt Ser-473 phosphorylation independent of mTORC1 inhibition. Oncogene 26:5655–5661.

    Article  PubMed  CAS  Google Scholar 

  22. Zuluaga S, Álvarez-Barrientos A, Gutiérrez-Uzquiza A et al (2007) Negative regulation of Akt activity by p38α MAP kinase in cardiomyocytes involves membrane localization of PP2A through interaction with caveolin-1. Cell Signal.

  23. Gratton JP, Morales-Ruiz M, Kureishi Y, Fulton D, Walsh K, Sessa WC (2001) Akt Down-regulation of p38 signaling provides a novel mechanism of vascular endothelial growth factor-mediated cytoprotection in endothelial cells. J Biol Chem 276:30359–30365.

    Article  PubMed  CAS  Google Scholar 

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The authors would like to thank Dr. Jasim Al-Rawi and Rick Morrison for supplying LTUR6 compound, which was synthesized in their laboratory. The authors would like to thank Dr. Mike Angove for his constant encouragement and support.


This work was funded by Australian Postgraduate Award and LaTrobe University Postgraduate Research Scholarship (PhD fellowship to Rejitha Suraj).

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Correspondence to Rejitha Suraj.

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Suraj, R., Al-Rawi, J. & Bradley, C. Inhibition of AKT signalling by benzoxazine derivative LTUR6 through the modulation of downstream kinases. Invest New Drugs 37, 779–783 (2019).

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  • Doxorubicin
  • Apoptosis
  • AKT
  • Chemosensitization