Comparison of Antitumor Activity of Some Benzothiophene and Thienothiophene Carboxanilides and Quinolones in 2D and 3D Cell Culture System

One of the main reasons for the high drug attrition rate in oncology is the poor clinical predictive power of 2D cancer cell lines cultures in vitro which are the standard assay used as screening assay to select new chemical entities (NKE) with potent anticancer activity. Therefore, there is increasing interest in developing 3D in vitro cell culture systems, as a primary screening assays which would represent a biologically more relevant assay system, due to similarity to physiological conditions in which tumors growth in living organism. Very important is to develop reproducible 3D cell line culture in vitro assays, feasible for the primary screening of NKEs platforms. Within this manuscript we have tested small platform of selected benzo[b]thieno, thieno[2,3-b]thiophene, and thieno[3,2-b]thiophene 2-carboxanilides, as well as their cyclic derivatives [2,3-c]quinolones, which already showed anti-proliferative activity on other cancer cell lines in 2D system. Platform was tested in 2D and 3D cancer cell culture assays on three human breast cancer cell lines (SK-BR-3, MDA-MB-231, T-47D). Those cell lines were selected on the basis of ability to growth and form cell spheres and also on different sensitivity to chemotherapeutic agents. We used doxorubicin as control compound due similar mode of action, (specific intercalation with the DNA double helix), as tested compound probably have. Obtained results in some cases showed significant disagreement, indicating that in early screening selection of active compounds only on 2D activity basis we could pick up false positive compounds (active only on 2D cell culture lines and not on 3D cell lines for which it is clamed that are more similar to real physiological conditions for tumor growth). One possibility for obtained discrepancy of results obtained on 2D and 3D cell cultures could be physico-chemical properties of compounds. Therefore, we analyzed some physico-chemical properties of active compounds as chrom logD values and calculated structural parameters: number of hydrogen bond donors and acceptors, calculated logP and logD values, molecular weight, ionization constants (pKa), number of aromatic rings, number of rotatable bonds and polar surface area. Association of physico-chemical descriptors with observed anti-proliferative activity has been investigated. Basicity, molecular weight and number of H-bond donors are found to be main factors contributing to the anti-proliferative effect of investigated compounds for both 2D and 3D cell cultures.