According to the 2016 NCCN guidelines Colon Cancer is the fourth most frequently diagnosed tumor and the second leading cause of cancer death in the USA, and the liver represents the frequent localization of colon cancer metastases. Reactivation or alteration of molecular pathways that control cellular differentiation and proliferation play a role in the development and progression of both familiar and sporadic colon cancer [1, 2]. It has been demonstrated that the presence of active Hedgehog-GLI activity in epithelial tumor cells of colorectal cancer is essential for tumor growth, recurrence and metastatic growth, and regulates the behavior of human colorectal cancer (CRC) stem cells in vivo [3]. Our data demonstrate that Hepatocellular Carcinoma (HCC) regulates Hepatic Stellate Cells¿ (HSC) viability via paracrine signaling by modulating Hedgehog pathway [4]. These data suggest that the use of an Hedgehog (Hh) inhibitor may interfere with the metastatic spread and in particular with the liver localization of Colon Cancer metastases. Moreover, there are evidences of interplay between Hedgehog and TGF-ß pathways in both normal and malignant tissues. In particular, TGF-ß induces GLI1 in a GLI2-dependent manner independently from Smoothened (SMO) [5]. Therefore, we decided to develop a murine model of colorectal cancer liver metastases and to evaluate the role of a pharmacologic Hedgehog inhibitor in the natural history of the CRC. In addition to that, the effect of the synergic inhibition of Hh and TGF-ß pathways will be tested both in our in-vitro settings and in our animal model of liver metastasis, to study the changes in metastases spreading and invasiveness.
Our preliminary data show that inhibition of Hedgehog pathway with specific pharmacological inhibitor reduced cell proliferation, migration and invasion, which were associated with upregulation of p21, Cyt18 and E-cadherin and with downregulation of CycD1 and Snail1. Also, SMO genetic silencing or treatment with 5E1 mAb induced reversion towards an epithelial phenotype. 1H-NMR metabolomic profiles showed a higher consumption of pyruvate, succinate and tyrosine as well as a lower consumption of valine, glutamate and phenylalanine upon Hh-Antag treatment. Our unpublished results suggest that an Hedgehog autocrine signaling loop fosters CC invasion integrating cell proliferation, cell plasticity, glucose/aminoacids metabolism, and encourage to further studies to challenge the relevance of this discovery. A Randomized phase II trial comparing the efficacy of Vismodegib, a Smo inhibitor, versus placebo with FOLFOX (Fluorouracil and Oxaliplatin) or FOLFIRI (Fluorouracil and Irinotecan) and Bevacizumab by Berlin and colleagues [14] recently demonstrated that Vismodegib doesn¿t show an incremental benefit to standard-of-care first-line treatment for mCRC in a population of previously untreated patients with metastatic colorectal cancer. However, there are several concerns and possible explanation for these results, as reported from the authors themselves. For example, the authors propose the existence of a negative pharmacokinetic interaction between Vismodegib and other regimen component. Here we propose a different end point, since we want to investigate the effect of hedgehog pathway inhibition in modulating colorectal cancer metastatic spread to the liver. Our study, exploring the possibility to interfere with liver metastasis, may have a high translational relevance and further therapeutic applications. Moreover, we propose a novel approach, inhibiting both Hedgehog and TGF- ß pathways. In fact, as reported by Perrot and colleagues, there are evidences of a GLI2-dependent activation of GLI1, an important component of the Hedgehog pathway, mediated by TGF-ß independently from SMO [5]. GLI1 is also reported to downregulate the expression of the E-Cadherine and thus promoting metastatic spread. Therefore, we can hypothesize that inhibiting those two pathways can reduce colon cancer metastatic spread to the liver.
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