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Updated: May 2, 2026
Simple and Fast Rolling Circle Amplification-Based Detection of Topoisomerase 1 Activity in Crude Biological Samples
Published on: December 2, 2022
Context-dependent antagonism between Akt inhibitors and topoisomerase poisons
Marina Gálvez-Peralta1, Karen S Flatten, David A Loegering
1Divisions of Oncology Research (M.G.-P., K.S.F., D.A.L., K.L.P., P.A.S., S.H.K.) and Medical Oncology (C.E.), Department of Oncology and Department of Molecular Pharmacology & Experimental Therapeutics (S.H.K.), Mayo Clinic College of Medicine, Rochester, Minnesota.
Abstract:
Signaling through the phosphatidylinositol-3 kinase (PI3K)/Akt pathway, which is aberrantly activated in >50% of carcinomas, inhibits apoptosis and contributes to drug resistance. Accordingly, several Akt inhibitors are currently undergoing preclinical or early clinical testing. To examine the effect of Akt inhibition on the activity of multiple widely used classes of antineoplastic agents, human cancer cell lines were treated with the Akt inhibitor A-443654 [(2S)-1-(1H-indol-3-yl)-3-[5-(3-methyl-2H-indazol-5-yl)pyridin-3-yl]oxypropan-2-amine; ATP-competitive] or MK-2206 (8-[4-(1-aminocyclobutyl)phenyl]-9-phenyl-2H-[1,2,4]triazolo[3,4-f][1,6]naphthyridin-3-one;dihydrochloride; allosteric inhibitor) or with small interfering RNA (siRNA) targeting phosphoinositide-dependent kinase 1 (PDK1) along with cisplatin, melphalan, camptothecin, or etoposide and assayed for colony formation. Surprisingly different results were observed when Akt inhibitors were combined with different drugs. Synergistic effects were observed in multiple cell lines independent of PI3K pathway status when A-443654 or MK-2206 was combined with the DNA cross-linking agents cisplatin or melphalan. In contrast, effects of the Akt inhibitors in combination with camptothecin or etoposide were more complicated. In HCT116 and DLD1 cells, which harbor activating PI3KCA mutations, A-443654 over a broad concentration range enhanced the effects of camptothecin or etoposide. In contrast, in cell lines lacking activating PI3KCA mutations, partial inhibition of Akt signaling synergized with camptothecin or etoposide, but higher A-443654 or MK-2206 concentrations (>80% inhibition of Akt signaling) or PDK1 siRNA antagonized the topoisomerase poisons by diminishing DNA synthesis, a process that contributes to effective DNA damage and killing by these agents. These results indicate that the effects of combining inhibitors of the PI3K/Akt pathway with certain classes of chemotherapeutic agents might be more complicated than previously recognized.
Insights
Combining phosphatidylinositol-3 kinase (PI3K)/Akt pathway inhibitors with chemotherapy shows complex interactions. Synergistic effects were seen with DNA cross-linking agents, but varied with topoisomerase poisons depending on PI3KCA mutation status and inhibitor concentration.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Aberrant activation of the phosphatidylinositol-3 kinase (PI3K)/Akt pathway is common in carcinomas, promoting apoptosis resistance and drug resistance.
- Akt inhibitors are under investigation for cancer therapy, necessitating an understanding of their interactions with existing chemotherapeutics.
Purpose of the Study:
- To investigate the effects of inhibiting the Akt pathway on the efficacy of various antineoplastic agents.
- To determine how Akt inhibition interacts with DNA cross-linking agents and topoisomerase poisons in human cancer cell lines.
Main Methods:
- Human cancer cell lines were treated with Akt inhibitors (A-443654, MK-2206) or PDK1 siRNA.
- Combinations were tested with DNA cross-linking agents (cisplatin, melphalan) and topoisomerase poisons (camptothecin, etoposide).
- Colony formation assays were used to assess drug effects.
Main Results:
- Synergistic effects were observed when combining Akt inhibitors with cisplatin or melphalan, irrespective of PI3K pathway status.
- In PI3KCA-mutated cells, Akt inhibition enhanced the effects of camptothecin or etoposide.
- In PI3KCA-wild-type cells, high concentrations of Akt inhibitors or PDK1 siRNA antagonized camptothecin/etoposide by reducing DNA synthesis.
Conclusions:
- The combination of PI3K/Akt pathway inhibitors with chemotherapy yields complex outcomes that are drug- and context-dependent.
- Understanding these interactions is crucial for optimizing cancer treatment strategies involving Akt inhibition.
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