The areas of research in LET:

a)      Research activity that is mainly dealing with the complex networks of regulation of the cell cycle and death in tumor cells, thus contributing to better understanding of how anticancer agents induce cell death and how defects in death pathways influence the therapy outcome. We have been especially interested in the role of p53 gene (the main regulator of most of cell-responses to treatment and one of the most often mutated genes in human cancers) and p21^WAF1/CIP1 gene that plays a major role in cell senescence, but contradictory role in apoptosis and underexplored role in autophagy. The emphasis of this research is to correlate specific DNA lesion that is induced by antitumor compounds with the final effect (specific cell response). Special accent has been put on the importance of non-apoptotic responses to anticancer agents, such as cell senescence, mitotic catastrophe and autophagy and to the interdependency of apoptotic and non-apoptotic mechanisms. We have studied mechanisms by which p21 gene regulate various cell responses and weather and how p21 characterize tumor cells with regard to chemosensitivity. (MSES project “The role of different cell death responses to DNA-damage treatment” (2007-2013))

1. Kraljević Pavelić, S; Čačev, T; Kralj, M. A dual role of p21waf1/cip1 gene in apoptosis of HEp-2 treated with cisplatin or methotrexate. Cancer Gene Ther (2008) 15:576-590.
2. Kraljević Pavelić, S#; Marjanović, M#; Poznić, M; Kralj, M. (2009) Adenovirally-mediated p53 overexpression diversely influence the cell cycle of HEp-2 and CAL 27 cell lines upon cisplatin and methotrexate treatment. J Cancer Res Clin Oncol 135:1747-1761. #First autor – equal conribution
3. Mikecin A-M, Walker L, Kuna M, Raucher D. Thermally targeted p21 peptide enhances bortezomib cytotoxicity in androgen-independent prostate cancer cell lines. Anticancer Drugs (2014) 2: 189–199.

b)      We have been collaborating with a great number of organic synthesis research groups from Croatia and also other European countries. We have developed an in vitro/in silico platform for screening of potential novel antitumor compounds. Especially active/selective newly synthesized compounds are being further studied by more sophisticated molecular biology methods in order to more closely elucidate their mechanisms of action. Such a highly interdisciplinary research has resulted in the unique expertise in medicinal/pharmaceutical chemistry and in a great number of publications in respectable medicinal chemistry journals, along with discovery of several lead compounds.

1. Hranjec, M; Kralj, M*; Piantanida, I; Sedić, M; Šuman, L; Pavelić, K; Karminski-Zamola, G*. Novel cyano- and amidino-substituted derivatives of styryl-2-benzimidazoles and benzimidazo[1, 2-a]quinolines. Synthesis, photochemical synthesis, DNA binding, and antitumor evaluation, part 3. J Med Chem 50 (2007) , 23; 5696,
2. Ester, K; Hranjec, M; Piantanida, I; Ćaleta, I; Ivana, J; Pavelić, K; Kralj, M*; Karminski-Zamola, G*. Novel Derivatives of Pyridyl-Benzo[b]thiophene-2-carboxamides and Benzo[b]thieno[2, 3- c]naphthyridin-2-ones: Minor Structural Variations Provoke Major Differences of Antitumor Action Mechanisms. J Med Chem 52:2482-2492 (2009).
3. Supek, F^#; Kralj, M^#; Marjanović, M; Šuman, L; Šmuc, T; Krizmanić, I; Žinić, B. Atypical cytostatic mechanism of N -1-sulfonylcytosine derivatives determined by in vitro screening and computational analysis. Invest New drugs (2008) 26:97-110., ^#First autor – equal conribution
4. Perin, N; Martin Kleiner, I; Nhili, R; Laine, W; David-Cordonnier, M-H; Vugrek, O; Karminski-Zamola, G; Kralj, M*; Hranjec, M*. Biological activity and DNA binding studies of 2-substituted benzimidazo[1, 2-a]quinolines bearing different amino side chains. MedChemComm 4 (2013)  1537-1550.
5. Basarić, N; Mlinarić-Majerski, K; Kralj, M. Quinone methides: photochemical generation and its application in biomedicine. Current Organic Chemistry (2014) 18; 3-18.
6. Kralj, M*; Uzelac, L; Wang, Yu-H; Wan, P; Tireli, M; Mlinarić-Majerski, K; Piantanida, I; Basarić, N*. Enhancement of antiproliferative activity by phototautomerization of anthrylphenols. Photochem. Photobiol. Sci.( 2015) 14:1082-1092.
7. Levatić, J; Ćurak, J; Kralj, M; Šmuc, T; Osmak, M; Supek, F. Accurate Models for P-gp Drug Recognition Induced from a Cancer Cell Line Cytotoxicity Screen. J Med Chem 56 (2013) 5691-5708.

c)      The research has been dominantly focused on DNA-damaging agents and comparing structure, DNA interactions, and their biological effects. Recently, however, we have opened a new area of research on the potential antitumor ability ofpotassium ionophores. We are mostly interested in crown ether compounds, which are also known to transfer potassium ions through membranes. We have been studying the role of ion (especially potassium) transport in chemosensitivity and potassium ionophores as potential antitumor compounds. A natural potassium ionophore salinomycin was recently identified as cancer stem cells’ (CSC) selective substance, but the precise mechanism of its selectivity remains elusive. Consequently, our current research has been focused on discovering novel CSC-selective compounds, based on potassium transport disturbance. We have been using cells that have passed through epithelial-mesenchymal transition (EMT) and have characteristics of CSCs. We have been striving to recognize novel biomarkers for identification and targeting CSCs, as well as elucidate differential effects of salinomycin on EMT cells. (Croatian Science Foundation project “A multidisciplinary approach to discover selective drugs targeting cancer stem cells: The role of potassium transport - MultiCaST“)

1. M. Marjanović, M. Kralj*, F. Supek, L. Frkanec, I. Piantanida, T. Šmuc, Lj. Tušek-Božić. Antitumor potential of crown ethers: structure activity relationships, cell cycle disturbances and cell death studies of a series of ionophores. J Med Chem (2007) 50:1007-1018
2. Supek, F; Šumanovac Ramljak, T; Marjanović, M; Buljubašić, M; Kragol, G; Ilić, N; Šmuc, T; Zahradka, D; Mlinarić-Majerski, K*; Kralj, M*. Could LogP be a principal determinant of biological activity in 18-crown-6 ethers? Synthesis of biologically active adamantane-substituted diaza-crowns. Eur J Med Chem 46(2011) 3444-3454
3. Kralj, M*; Tušek-Božić, Lj; Frkanec, L. Biomedical Potentials of Crown Ethers: Prospective Antitumor Agents. ChemMedChem (2008) 3:1478-1492
4. US Patent No. US 8,389,505 B2 (2013): Marijeta Kralj, Kata Majerski, Marko Marjanović i Tatjana Šumanovac Ramljak „Adamantane derivatives of aza-crown ethers and their use in treatment of tumor“
5. P20090355 (2015)HR patent: Marijeta Kralj, Kata Majerski, Marko Marjanović i Tatjana Šumanovac Ramljak. Adamantanski derivati aza-krunastih etera i njihova upotreba u terapiji tumora.
6. Guberović I^#, Marjanović M^#, Mioč M, Ester K, Martin-Kleiner I, Šumanovac Ramljak T, Mlinarić-Majerski K, Kralj M. Crown ethers reverse P-glycoprotein-mediated multidrug resistance in cancer cells. Sci Rep, under revision. ^#First autor – equal conribution