Expression of the active Notch1 decreases MTC tumor growth in vivo - PubMed (original) (raw)

Expression of the active Notch1 decreases MTC tumor growth in vivo

Renata Jaskula-Sztul et al. J Surg Res. 2011 Nov.

Abstract

Background: Human medullary thyroid cancer (MTC) is a neuroendocrine (NE) tumor, derived from thyroid C-cells. Besides surgery, there are no curative therapies for MTC. This emphasizes the need for the development of new therapies. In MTC, Notch1 signaling pathway is absent and Notch1 activation in MTC-TT cells has been shown to reduce growth and NE markers in vitro. While the in vitro studies will provide insight into the potential mechanisms by which Notch inhibits growth, only by in vivo model one can recreate the conditions found in patients with MTC and assess effects on metastatic potential and microscopic disease.

Materials and methods: Doxycycline inducible TT-NOTCH1 cells were utilized in a murine subcutaneous xenograft model to study tumor development and growth. Doxycycline was used to induce the expression of Notch1 in these tumors.

Results: Measurements of tumor volume showed that doxycycline treated mice had slower tumor growth than control mice. Western blot analysis of tumor lysates demonstrated activation of Notch1 protein only in doxycycline treated mice suggesting that active Notch1 slowed tumor growth. Furthermore, this activation led to a significant reduction in the levels of achaete-scute complex-like1 and chromogranin A important NE markers.

Conclusion: Based on these data, activation of Notch signaling pathway could be a therapeutic strategy to treat patients with MTC.

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Figures

Fig. 1. Induction of active Notch1 caused reduction in NE markers

Lysates from TT-NOTCH1 cells treated with or without doxycycline for 4 days showed marked induction of Notch1 only after doxycycline treatment. This is associated with a significant reduction in CgA and ASCL1. GAPDH was used as loading control.

Fig. 2. Overexpression of Notch1 suppresses MTC tumor growth in nude mice

A. Doxycycline induced expression of Notch1 resulted in an average 57% reduction of tumor volume (p<0.05) compared to the control group after 28 days treatment. Standard deviation (SD) was calculated for the control and treated group. B. Tumor weights at necropsy have showed 58% reduction in the group treated with doxycycline.

Fig. 2. Overexpression of Notch1 suppresses MTC tumor growth in nude mice

Fig. 3. Doxycycline dependant expression of Notch1 in MTC xenografts suppresses NE markers

Western blot analysis showed doxycycline induction of the Notch1 intracellular domain (NICD1) in MTC cells (TT-NOTCH1) implanted into nude mice and protein expression of NE tumor markers, ASCL1 and CgA, down regulated by Notch1. GAPDH was used as a protein loading control.

Fig. 4. Notch1 expression suppresses ASCL1 mRNA

Quantitative real-time PCR has shown a 2 fold reduction in ASCL1 mRNA in mice treated with doxycycline compared to the control group.

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Expression of the active Notch1 decreases MTC tumor growth in vivo - PubMed (original) (raw)