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Hyaluronan (HA) is one of the major components of the extracellular matrix. Several solid tumors produce high levels of HA, which promotes survival and multidrug resistance (MDR). HA oligomers (oHAs) can block HA effects. However, little is known about the role of HA in hematological malignancies. The aim of this work was to determine whether HA or its oligomers can modulate the proliferation of leukemia cells as well as their effect on MDR. Receptors and signaling pathways involved were also analyzed. For this purpose, the human leukemic cell lines K562 and Kv562, which are sensitive and resistant to Vincristine (VCR), respectively, were used. We demonstrated that HA induced cell proliferation in both cell lines. On K562 cells, this effect was mediated by cluster differentiation 44 (CD44) and activation of both phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) and mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathways, whereas on Kv562 cells, the effect was mediated by receptor for hyaluronan-mediated motility (RHAMM) and PI3K/Akt activation. The inhibition of HA synthesis by 4-methylumbelliferone (4MU) decreased cell line proliferation and sensitized Kv562 to the effect of VCR through P-glycoprotein (Pgp) inhibition, in both cases with senescence induction. Moreover, oHAs inhibited K562 proliferation mediated by CD44 as well as Akt and ERK down-regulation. Furthermore, oHAs sensitized Kv562 cells to VCR by Pgp inhibition inducing senescence. We postulate that the synthesis of HA would promote leukemia progression mediated by the triggering of the above-mentioned proliferative signals. These findings highlight the potential use of oHAs and 4MU as coadjuvant for drug-resistant leukemia.

Here we present evidence that allows us to consider a combined therapy regimen comprising an autophagy inhibitor and a MAPK or NF-kB pathway inhibitor as a possible treatment strategy for pancreatic cancer.

Pancreatic cancer is an aggressive disease. Its incidence has increased over the last two decades. It is currently the fourth cause of death among cancers in the western world. Unfortunately, systemic chemotherapy still relies on just a few drugs which until now have produced unsatisfactory results. Gemcitabine (2'-2'-difluorodeoxycytidine) is currently the standard chemotherapy treatment at all stages of pancreatic adenocarcinoma. Survival benefit and clinical impact however remain moderate due to a high degree of intrinsic and acquired resistance. Autophagy plays an important role in cell death decision but can also protect cells from various apoptotic stimuli. We investigated the function of autophagy in pancreatic carcinoma cells, which are frequently insensitive to standard chemotherapeutic agents. Here, we demonstrate that autophagy is one of the mechanisms responsible for the refractory response of pancreatic tumors to gemcitabine. We present evidence in vitro and in vivo that proves autophagy plays a protective role in pancreatic ductal carcinoma cells, preventing them from entering the apoptotic pathway after stimulus with gemcitabine, thus contributing to treatment resistance. A better understanding of the role in the process may help in the discovery of new strategies to overcome tumor drug resistance in this aggressive disease.

Trypanosoma cruzi is the causative agent of Chagas’ disease, which is a major endemic disease in Latin America and is recognized by the WHO as one of the 17 neglected tropical diseases in the world. Psilostachyin and psilostachyin C, two sesquiterpene lactones isolated from Ambrosia spp., have been demonstrated to have trypanocidal activity. Considering both the potential therapeutic targets present in the parasite, and the several mechanisms of action proposed for sesquiterpene lactones, the aim of this work was to characterize the mode of action of psilostachyin and psilostachyin C on Trypanosoma cruzi and to identify the possible targets for these molecules. Psilostachyin and psilostachyin C were isolated from Ambrosia tenuifolia and Ambrosia scabra, respectively. Interaction of sesquiterpene lactones with hemin, the induction of oxidative stress, the inhibition of cruzipain and trypanothione reductase and their ability to inhibit sterol biosynthesis were evaluated. The induction of cell death by apoptosis was also evaluated by analyzing phosphatidylserine exposure detected using annexin-V/propidium iodide, decreased mitochondrial membrane potential, assessed with Rhodamine 123 and nuclear DNA fragmentation evaluated by the TUNEL assay. Both STLs were capable of interacting with hemin. Psilostachyin increased about 5 times the generation of reactive oxygen species in Trypanosoma cruzi after a 4h treatment, unlike psilostachyin C which induced an increase in reactive oxygen species levels of only 1.5 times. Only psilostachyin C was able to inhibit the biosynthesis of ergosterol, causing an accumulation of squalene. Both sesquiterpene lactones induced parasite death by apoptosis. Upon evaluating the combination of both compounds, and additive trypanocidal effect was observed. Despite their structural similarity, both sesquiterpene lactones exerted their anti-T. cruzi activity through interaction with different targets. Psilostachyin accomplished its antiparasitic effect by interacting with hemin, while psilostachyin C interfered with sterol synthesis.

Chronic myeloid leukemia (CML) is a myeloproliferative syndrome characterized by the presence of the Philadelphia chromosome which encodes a constitutively activated tyrosine kinase (BCR-ABL). The first line treatment for CML consists on BCR-ABL inhibitors such as Imatinib. Nevertheless, such treatment may lead to the selection of resistant cells. Therefore, it is of great value to find molecules that enhance the anti-proliferative effect of first-line drugs. Hyaluronan is the main glycosaminglican of the extracellular matrix which is involved in tumor progression and multidrug resistance. We have previously demonstrated that the inhibition of hyaluronan synthesis by 4-methylumbelliferone (4MU) induces senescence and can revert Vincristine resistance in CML cell lines. However, the effect of 4MU on Imatinib therapy remains unknown. The aim of this work was to determine whether the combination of 4MU with Imatinib is able to modulate the proliferation as well as apoptosis and senescence induction in human CML cell lines. For this purpose the ATCC cell line K562, and its multidrug resistant derivate, Kv562 were used. Cells were exposed to 4MU, Imatinib or a combination of both. We demonstrated that 4MU and Imatinib co-treatment abrogated the proliferation of both cell lines. However, such co-treatment did not increase the levels of apoptosis when compared with the treatment with Imatinib alone. For both cell lines the mechanisms of tumor suppression involved was senescence, since the combination of 4MU and Imatinib arrested the cell cycle and increased senescence associated β-galactosidase activity and senescence associated heterochromatin foci presence when compared to each drug alone. Moreover, 4MU, Imatinib and 4MU + Imatinib decreased pAkt/Akt ratio in both cell lines and reduced the pERK/ERK ratio only in K562 cells. These findings highlight the potential use of 4MU together with Imatinib for CML therapy.