Molecular Mechanisms of Chloroquine and Hydroxychloroquine Used in Cancer Therapy.

Tumour relapse, chemotherapy resistance, and metastasis continue to be unsolved issues in cancer therapy. A recent approach has been to scrutinise drugs used in the clinic for other illnesses and modify their structure to increase selectivity to cancer cells. Chloroquine (CQ) and hydroxychloroquine (HCQ), known antimalarials, have successfully treated autoimmune and neoplastic diseases. CQ and HCQ, well-known lysosomotropic agents, induce apoptosis, downregulate autophagy, and modify the tumour microenvironment. Moreover, they affect the Toll 9/NF-κB receptor pathway, activate stress response pathways, enhance p53 activity and CXCR4-CXCL12 expression in cancer cells, which would help explain their effects in cancer treatment. These compounds can normalise the tumourassociated vasculature, promote the activation of the immune system, change the phenotype of tumour-associated macrophages (from M2 to M1), and stimulate cancer-associated fibroblasts. We aim to review the historical aspects of CQ and its derivatives and the most relevant mechanisms that support the therapeutic use of CQ and HCQ for the treatment of cancer.

Caracasine, An ent-kaurane Diterpene with Proapoptotic and Pro-differentiator Activity in Human Leukaemia Cell Lines.

BACKGROUND: Kaurane-type diterpenoids, obtained from various natural sources, have shown many biological activities, including anti-inflammatory and antitumor effects. Caracasine, an ent-kaurane diterpenoid isolated from the flowers of Croton micans, was shown to induce apoptosis in leukaemia cell lines. OBJECTIVE: The present study aimed to ascertain the compound's mechanism of cell death induction using two leukaemia cell lines, Jurkat E6.1 (T cell) and HL-60 (promyeloblast cells). METHODS: Cell death in Jurkat and HL60 cells were evaluated by flow cytometry for apoptosis with annexin-V/PI, mitochondrial membrane potential disturbance, changes in cell cycle, CD95 expression, caspase activation, Nuclear Factor kappa B inhibition, and differentiation into a neutrophil-like cell (dHL60). RESULTS: Caracasine (10 µM) increased the G0/G1 phase in Jurkat and arrested the cell cycle in the S phase in HL60. Caracasine increased CD95 expression (p<0.01 in Jurkat and p<0.05 in HL60) and caspase-8 activation (p<0.001 in Jurkat and p<0.05 in HL60). Caspase-9 was activated in both cell lines (p<0.001) along with the decline in mitochondrial Δψm (p<0.05 in Jurkat and p<0.001 in HL60). In HL60 cells, the kaurane induced neutrophil differentiation was assessed by CD40 expression and reactive oxygen species production. In Jurkat cells, caracasine inhibited the NF-κB pathway in cells pretreated with PHA to activate the NF-κB pathway, suggesting a possible role in inflammatory diseases. CONCLUSION: Caracasine induced apoptosis through the intrinsic and extrinsic pathways in both cell lines were evaluated which could be the leading structure for new anti-leukemic and anti-inflammatory drugs.

Caracasine acid, an ent-3,4-seco-kaurene, promotes apoptosis and cell differentiation through NFkB signal pathway inhibition in leukemia cells.

Caracasine acid (CA) is an ent-3,4-seco-kaurene isolated from the plant Croton micans. Decreased cancer cell lines viability was reported upon CA treatment. The present study aimed to investigate the mechanism of CA induced cytotoxicity using two human cell lines, Jurkat E6.1 (human cell T lymphoma) and HL-60 (human acute promyelocytic leukemia). Significant increases of apoptotic cell death markers upon CA treatment were observed: annexin-V positiveness, potential mitochondrial disturbances, cell cycle changes, caspase activation, and CD95 expression. These effects were not detected in normal lymphocytes. CA induced the appearance of Bax, cleaved caspase 3, and cytochrome c release in Jurkat cells, and cleaved caspase 3 and phosphorylated p53 in HL60 cells. Likewise, downregulation of anti-apoptotic proteins such as Bcl-x (Jurkat), Bcl-2, and XIAP (HL60) was observed with CA treatment. Both pathways, intrinsic and extrinsic were activated when cell lines were treated with CA. NF-κB p65 inhibition was observed in Jurkat cells and cell differentiation in HL-60 cells. CA could be a potential leader compound for the development of new drugs for leukemia treatment in humans.

Cytotoxic effects of Fisturalin-3 and 11-Deoxyfisturalin-3 on Jurkat and U937 cell lines.

BACKGROUND: Fisturalines are bromotyrosine compounds isolated from marine sponges. Previous studies have shown antineoplasic, antiviral and antibacterial effects in Vitro; however, the possible effects of these compounds in hematologic malignancies have not been assessed. METHODS: In the present study, the antiproliferative and pro apoptotic effects of Fistularin-3 (F) and 11-Deoxyfistularin-3 (DF) were assessed using the MTT method and annexin V/propidium iodide by flow cytometry using the cell lines: Jurkat E6.1 and U937. In addition, the cell cycle was assessed by flow cytometry. RESULTS: Inhibition of the proliferative response was concentration and time dependent. The IC50 of F was 7.39 and 8.10 µM for Jurkat E6.1 and U937 respectively. At 24 and 48 h, in the U937 cell line, but not in the Jurkat cell line, both compounds induced up to 35% annexin V increase. Necrosis was not observed in any case. Compound F induced, in both cell lines, a decrease in the number of cells in the S phase and increase in the G0/G1 phase. In the Jurkat cell line only, there was an increase in the number of cells in the G2/M phase. Compound DF was not as effective as F. CONCLUSIONS: F is more active than DF in repressing the cell cycle and inducing apoptosis. Both compounds are potentially useful in the development of new drugs to treat hematologic malignancies.