GHRH Antagonist Causes DNA Damage Leading to p21 Mediated Cell Cycle Arrest and Apoptosis in Human Colon Cancer Cells

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Published on Thursday, 28 May 2020

Abstract

We investigated the mechanisms of inhibitory effect of growth hormone-releasing hormone (GHRH) antagonist JMR-132 on the growth of HT29, HCT-116 and HCT-15 human colon cancer cells in vitro and in vivo.

High-affinity binding sites for GHRH and mRNA for GHRH and splice variant-1 (SV1) of the GHRH receptor were found in all three cell lines tested.

Proliferation of HT-29, HCT-116 and HCT-15 cells was significantly inhibited in vitro by JMR-132.

Time course studies revealed that the treatment of human HCT-116 colon cancer cells with 10 muM GHRH antagonist JMR-132 causes a significant DNA damage as shown by an increase in olive tail moment (OTM) and loss of inner mitochondrial membrane potential (Delta Psi m).

Western blotting demonstrated a time-dependent increase in protein levels of phospho-p53 (Ser46), Bax, cleaved caspase-9, -3, cleavage of poly(ADP-ribose)polymerase (PARP) and a decrease in Bcl-2 levels. An augmentation in cell cycle checkpoint protein p21(Waf1/Cip1) was accompanied by a cell cycle arrest in S-phase. DNA fragmentation visualized by the comet assay and the number of apoptotic cells increased time dependently as determined by flow cytometric annexinV and PI staining assays.

In vivo, JMR-132 decreased the volume of HT-29, HCT-116 and HCT-15 tumors xenografted into athymic mice up to 75% (p < 0.05) and extended tumor doubling time (p<0.001).

Our observations suggest that GHRH antagonist JMR-132 exerts its antiproliferative effect on experimental colon cancer cells through p21(Waf1/Cip1) mediated S-phase arrest along with apoptosis involving the intrinsic pathway.

 



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- Official Web Site: The Di Bella Method;


 


- The Di Bella Method (A Fixed Part - Somatostatin, Octreotide, Sandostatin LAR, analogues and/or derivatives);

- Somatostatin in oncology, the overlooked evidences - In vitro, review and in vivo publications;

- Publication, 2018 Jul: Over-Expression of GH/GHR in Breast Cancer and Oncosuppressor Role of Somatostatin as a Physiological Inhibitor (from Di Bella's Foundation);

- Publication, 2018 Sep: The over-expression of GH/GHR in tumour tissues with respect to healthy ones confirms its oncogenic role and the consequent oncosuppressor role of its physiological inhibitor, somatostatin: a review of the literature (from Di Bella's Foundation);

- Publication, 2019 Aug: The Entrapment of Somatostatin in a Lipid Formulation: Retarded Release and Free Radical Reactivity (from Di Bella's Foundation);

- Publication, 2019 Sep: Effects of Somatostatin and Vitamin C on the Fatty Acid Profile of Breast Cancer Cell Membranes (from Di Bella's Foundation);

- Publication, 2019 Sep: Effects of somatostatin, curcumin, and quercetin on the fatty acid profile of breast cancer cell membranes (from Di Bella's Foundation);

- Publication, 2020 Sep: Two neuroendocrine G protein-coupled receptor molecules, somatostatin and melatonin: Physiology of signal transduction and therapeutic perspectives (from Di Bella's Foundation);

- The Di Bella Method (A Fixed Part - Bromocriptine and/or Cabergoline);

- Prolactin inhibitors in oncology - In vitro, review and in vivo publications;

- The Di Bella Method (A Fixed Part - Cyclophosphamide 50mg tablets and/or Hydroxyurea 500mg tablets, one or two per day);


 


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