J. Whitt1, A. Aune2, N. E. Avalon3, B. J. Baker3, H. Chen1, R. Jaskula-Sztul1 1University Of Alabama at Birmingham,Surgery,Birmingham, Alabama, USA 2Auburn University,Pharmacy,Auburn, ALABAMA, USA 3University of South Florida,Chemistry,Tampa, FLORIDA, USA
Introduction:
Neuroendocrine tumors (NETs) may arise from neuroendocrine cells located throughout the body, but usually occur in the gastrointestinal tract, lungs, or thyroid. Clinical trials have demonstrated a response rate of only 20% for single agent chemotherapy, leaving surgery as the only cure. However, the disease has usually metastasized by the time of diagnosis and widespread metastases make complete surgical resection impossible. Thus, there is a need to identify new therapeutics that will reduce NET development and progression, while improving patient quality of life. Recent experiments from our group and others have demonstrated a tumor suppressor function of the Notch pathway in NETs. Natural compounds belonging to the trichothecene and cytochalasin families have previously demonstrated anti-proliferative effects against various cancer types. We investigated the potential therapeutic effect of these compounds via the reduction of cell proliferation and activation of the Notch pathway in NETs.
Methods:
Fourteen compounds isolated from Myrothecium verrucaria and other fungal species were received from the Chemistry Department at the University of South Florida. NET cell lines BON, H727, TT, and MZ cell lines were treated with several concentrations of the compounds. For comparison, the non-cancerous WI-38 cell line was treated with the same concentrations of the compounds. Cell viability and cell cycle was assessed using MTT and flow cytometry, respectively. RNA was isolated from treated and untreated cells and RT-PCR was used to analyze changes in gene expression.
Results:
Two compounds significantly reduced cell viability in a dose-dependent manner. These compounds, Cytochalasin D and Roridin E, exhibited low micromolar IC50 values in BON, H727, MZ, and TT cell lines. Both Roridin E and Cytochalasin D increased Notch1 expression within 24 hrs, which was followed by a decrease in cell viability. Roridin E also decreased the expression of ASCL1, a transcription factor important for the development of NETs.
Conclusion:
Two compounds were identified as transcriptional activators of Notch1 signaling. This is the first time that a specific effect on Notch signaling has been identified for these compounds. Our findings support the development of these compound classes for the treatment and palliation of patients with NETs, which can significantly enhance the therapeutic outcome of NE cancer therapy while minimizing undesirable side-effects.