Adenovirus vectors with modified tropism for the treatment of colorectal cancer
Year: 2012
Type: dissertation
Abstract: Despite the rapid advance of cancer research and improvement of conventional therapeutic regimes like chemotherapy, surgery, immunotherapy or radiotherapy, cancer remains a leading cause of death worldwide. Metastatic disease normally represents the most deadly stage and leads to the poorest prognosis. The disseminated location of metastases makes it even more difficult nowadays for existing drugs to target tumors without damaging healthy tissues. The work presented in this Doctoral Thesis is aimed at developing targeted adenoviral vectors and regimes that can be applied to the treatment of cancer, especially colorectal cancer. Gene therapists have explored widely interactions of the viruses to cancer and normal cells and have proved that molecular modifications in the capsid can unleash striking differences in viral tropism. In this Doctoral Thesis, the utility of arginine-glycine-aspartic acid (RGD) targeting αvβ integrins substituted for the lysine-lysine-threonine-lysine (KKTK) domain of the fiber shaft or inserted in the HI-loop of adenovirus serotype 5 (Ad5) was evaluated for increased tumor targeting and antitumor efficacy. Both modifications increased gene transfer efficacy in colorectal cancer cell lines and improved the tumor to-normal ratio after systemic administration of the vector. Furthermore, antitumor potency was not compromised with RGD modified viruses suggesting that an increased safety profile did not involve any loss of therapeutic effect. Treatments based on adenovirus vectors should not have negative effects on tumor progression or metastases. In order to evaluate this possibility, we designed a novel murine model of human colorectal cancer (CoCa) to test our treatments. To this end, we have developed a readily imageable mouse model of colorectal cancer featuring highly reproducible formation of spontaneous liver metastases derived from intrasplenic primary tumors. We optimized several experimental variables, and found that the correct choice of cell line and genetic background of the recipient mice as well as their age, were critical for the establishment of a useful animal model. A magnetic resonance imaging (MRI) protocol was optimized for use with this mouse model, and demonstrated to be a powerful method for analyzing the antitumor effects of an experimental therapy. Poor spreading of the virus through tumor tissue is one of the major issues limiting efficacy of oncolytic adenoviruses, even after local administration by intratumoral injection. In this study, ECM-degrading proteases relaxin, hyaluronidase, elastase, and macrophage metalloelastase (MME) were used to increase oncolytic adenovirus spreading. Moreover, MME improved the overall antitumor/antitumour efficacy of oncolytic adenovirus in subcutaneous HCT116 xenografts. In a liver metastatic colorectal cancer model, intratumoral treatment of HT29 primary tumors with MME monotherapy or with oncolytic adenovirus inhibited tumor growth. Combination therapy showed no increased mortality in comparison to monotherapies. In addition, our work demonstrated for the first time in a metastatic animal model that MME, as a monotherapy or in combination with an oncolytic virus, does not increase tumor invasiveness. Co-administration of MME and oncolytic adenovirus may be a suitable approach for further optimization of metastatic colorectal cancer treatment. To summarise, we described how RGD moieties inserted in the fiber protein are capable of improving tumor targeting of wild-type or capsid-modified adenovirus vectors. We also showed that MME is a safe coadjuvant to be used in combination with oncolytic adenoviruses for intratumoral administration and we presented a highly optimized mouse model for liver metastasis of colorectal cancer.
Source: Työväentutkimus Vuosikirja
Author: Sergio Lavilla-Alonso
Language: English
Subfield: Genetics
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W1492658455