Titolo della tesi: Study of anti-cancer properties of novel curcumin derivatives in T-cell Acute Lymphoblastic Leukemia
T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy arising from the malignant transformation and clonal expansion of immature thymocyte precursors in the thymus and accounting for 10-15% of pediatric and 25% of adult cases of acute lymphoblastic leukemia. Although thanks to modern clinical management, T-ALL is considered curable, the prognosis for patients with relapsing/refractory disease is still dismal, therefore is needful to develop novel therapeutic agents for potential clinical improvement Considered that Notch signaling is among the key oncogenic pathways driving T-ALL pathogenesis and patient’s resistance to common chemotherapeutic agents, several approaches to target its pathway transduction have been actively explored for their anti-cancer proprieties in pre-clinical and clinical studies. However, clinical application of the most promising of them, the gamma-secretase inhibitors (GSI) and receptor/ligand blocking antibodies (Abs), is limited by low efficacy and/or severe adverse effects associated, thus encouraging the development of novel strategies.
In the last decade, naturally occurring compounds have been re-considered as lead candidates for anti-tumor treatments, and several of them interfering with Notch signaling have been suggested as potential anti-cancer approaches. Among naturally occurring phytochemicals promising to improve treatment efficiency in cancer patients and decrease adverse reactions, curcumin has proven effective in preclinical studies and has been recognized as molecules with good tolerability and safety profiles by FDA. At molecular levels, curcumin acts in a cell context-dependent manner by modulating a wide range of signaling pathways, including Nuclear Factor-ĸB (NF-ĸB), p53, Wnt/β-catenin, phosphoinositide 3-kinase / protein kinase B (PI3-Kinase/AKT), activator protein 1 (AP-1), and Mitogen-activated protein kinase (MAPK) pathway. Furthermore, the anti-tumor effects of curcumin and its derivatives have been linked to the repression of Notch1 signaling and its interacting pathways in some solid cancers. However, the efficacy of curcumin in T-cell leukemia has been investigated by few studies, and its anti-proliferative activity has been combined with the induction of caspase-dependent apoptotic cell death via inhibition of the survival signaling pathways PI3-kinase/AKT and by enhancing the generation of intracellular ROS, while there is no evidence on its interference with Notch signaling in T-ALL contexts. Furthermore, curcumin has demonstrated multiple effects on DNA damage and repair machinery both in healthy samples and experimental models of cancers, including normal lymphocytes and T-ALL cell lines, suggesting that it can protect against DNA damage or promote it by functioning as pro- or anti-oxidant and/or by favoring or interfering with the mechanisms implicated in the DNA repair in a context- and/or dosage-dependent manner.
Given the few evidence of curcumin's potential for leukemia treatment, we first investigated to which extent it counteracts the cell viability and Notch pathway activity and modulates the levels of factors involved in the DNA damage response in T-ALL cell lines with distinct Notch genes mutational states and different responsiveness to gamma-secretase inhibition. Subsequently, the research aimed to identify novel curcumin-derived compounds with potentiating proprieties against T-cell leukemia compared to the scaffold of origin.
Our results provide evidence that curcumin exerts anti-viability and anti-Notch effects at a low micromolar concentration of exposure in different T-ALL cell lines, and increased the levels of ATM/H2AX phosphorylation, PARP cleavage, and p27(Kip1) expression in a dose- and time-dependent fashion. However, the exposure to curcumin exerted anti-viability effects also in not-dependent from Notch signaling AML cells with similar strength than Notch-dependent T-ALL cell lines, and the constitutive enforced activation of Notch1 signaling did not rescue DND41 T-ALL cells from the anti-proliferative effects of the treatment. These findings suggest curcumin’s biological effects in T-ALL may not be strictly mediated by Notch inhibition but might be mainly dependent on the direct or indirect proprieties of the compound to induce DNA damage-dependent cell death. Nonetheless, the anti-tumorigenic activity of curcumin requires further investigation in T-ALL contexts and its in vivo application needs of new formulation solutions and/or the synthesis of novel curcumin analogues with improved pharmacological properties and similar safety profile.
Therefore, aimed to develop novel molecules with improved anti-leukemic activity than curcumin, seventeen its derivatives were designed, synthetized, and screened for anti-proliferative activity in T-ALL cells, highlighting the compound CD2066 as the most powerful bioactive compound of the series endowed with one hundred times increased anti-growth, anti-Notch and DNA damaging effects than the scaffold of origin. Of note, CD2066 anti-growth action was reverted by N1ICD overexpression, thus indicating that Notch1 inhibition is responsible, at least in part, for its growth inhibitory activity.
The increased potency of CD2066 compared to curcumin, the DNA-damaging action and the dependence of its anti-growth activity on Notch inhibition, indicate this compound as a novel potential therapeutic candidate against T-ALL and provide novel guidelines for future development of curcumin-based bioactive agents useful in the treatment of Notch-dependent leukemia.