Treatment of chemoresistant human glioblastoma cells with DNA aptamers for the development of new adjuvant therapies

Abstract

Glioblastoma multiforme (GBM) is the most common and aggressive primary malignant neoplasm of the CNS. Patients, even with an aggressive standard of treatment, have an average survival of 15 months and a 5-year survival of less than 5%. There are currently more than 150 cancer chemotherapy drugs approved worldwide, but only three are approved for the treatment of GBM patients. It is therefore essential that new therapeutic approaches are developed to improve the clinical outcome and survival of GBM patients. Several pieces of evidence have supported that GBM progression is driven by an intratumoral population of tumor stem cells. In this regard, glioblastoma tumor stem cells (GSCs) represent a promising target for therapeutic intervention. Aptamers are oligonucleotides selected from a combinatorial library that are capable of selectively binding to protein epitopes, in a similar way to the well-known monoclonal antibodies. Aptamers have a promising potential in diagnostic and therapeutic applications due to their high specificity, low molecular weight, low immunogenicity and ease of production/manipulation, competing with monoclonal antibodies. Prof. Henning Ulrich's group, from USP's Biochemistry Department, has characterized two DNA aptamers, called Apt9 and Apt17, which bind with high specificity to GSCs and are internalized by them, indicating their potential application as carrier molecules targeting tumor stem cells that are highly capable of surviving adverse conditions. On the other hand, the Laboratory of Neurochemistry and Cell Biology (LabNq) group at UFBA, led by Silvia L. Costa, has extensive experience in studies related to GBM physiology and the tumor niche, and in characterizing new therapeutic agents and their relationship with chemoresistance and immunomodulation. The current paradigm of cancer biology indicates the close relationship between immune evasion and inflammation for the composition and development of the tumor microenvironment. It is not yet clear how cancer shapes immune cells so that they have pro-tumor activity, but it is known that they have a unique molecular profile that changes according to the degree of GBM. The aim of this work is to characterize the effects and mechanisms of action of nanostructured DNA aptamers linked to TMZ or the flavonoid rutin with affinity for GSCs in order to develop new adjuvant therapies for chemoresistant human GBM. The specific objectives will be: i. Characterize the immunomodulatory and anti-tumor effects of nanostructured DNA aptamers combined with TMZ against GSC on the viability, proliferation and tumorigenicity of highly proliferative human GBM cells (already established lines) and in preclinical models of brain tumors, evaluating tumor progression and the inflammatory process; ii. Characterize signalling pathways and control the expression of genes related to chemoresistance, such as aryl hydrocarbon receptors of aptamers that are more efficient in their anti-tumour effects; We propose that iii. Validate the effects of aptamers linked to TMZ and rutin established with selection against tumor cell lines in cells from tumor tissue explants from patients established in LabNq's Biobank. The project will be developed mainly by researchers, post-doctoral students and graduate and undergraduate students who are part of the LabNq group (ICS/UFBA) and the groups of Henning Ulrich and Claudiana Lameu (IQ/USP). The team is multidisciplinary and will bring together expertise to achieve the objectives and thus bring new advances in drug development and application in accessible and complementary adjuvant therapy for malignant brain tumors. Based on the results obtained, the aim is to solidify the scientific basis for the possible use of aptamers as anti-tumorigenic adjuvants in GBM therapy. (AU)