Simultaneous evaluation of viability and Bcl-2 in small-cell lung cancer

Novel 4-Azapregnene Derivatives as Potential Anticancer Agents: Synthesis, Antiproliferative Activity and Molecular Docking Studies

A series of novel 21E-arylidene-4-azapregn-5-ene steroids has been successfully designed, synthesized and structurally characterized, and their antiproliferative activity was evaluated in four different cell lines. Within this group, the 21E-(pyridin-3-yl)methylidene derivative exhibited significant cytotoxic activity in hormone-dependent cells LNCaP (IC₅₀ = 10.20 µM) and T47-D cells (IC₅₀ = 1.33 µM). In PC-3 androgen-independent cells, the steroid 21E-p-nitrophenylidene-4-azapregn-5-ene was the most potent of this series (IC₅₀ = 3.29 µM). Considering these results, the 21E-(pyridin-3-yl)methylidene derivative was chosen for further biological studies on T47-D and LNCaP cells, and it was shown that this azasteroid seems to lead T47-D cells to apoptotic death. Finally, molecular docking studies were performed to explore the affinity of these 4-azapregnene derivatives to several steroid targets, namely 5α-reductase type 2, estrogen receptor α, androgen receptor and CYP17A1. In general, compounds presented higher affinity to 5α-reductase type 2 and estrogen receptor α.

Curzerene antileishmania activity: Effects on Leishmania amazonensis and possible action mechanisms

Leishmaniasis is a set of infectious diseases with high rates of morbidity and mortality, it affects millions of people around the world. Treatment, mainly with pentavalent antimonials, presents significant toxicity and many cases of resistance. In previous works we have demonstrated the effective and selective antileishmanial activity of Eugenia uniflora L. essential oil, being constituted (47.3%) by the sesquiterpene curzerene. Considering the high rate of parasite inhibition demonstrated for E. uniflora essential oil, and the significant presence of curzerene in the oil, this study aimed to evaluate its antileishmania activity and possible mechanisms of action. Curzerene was effective in inhibiting the growth of promastigotes (IC₅₀ 3.09 ± 0.14 µM) and axenic amastigotes (EC₅₀ 2.56 ± 0.12 µM), with low cytotoxicity to RAW 264.7 macrophages (CC₅₀ 83.87 ± 4.63 µM). It was observed that curzerene has direct effects on the parasite, inducing cell death by apoptosis with secondary necrotic effects (producing pores in the plasma membrane). Curzerene proved to be even more effective against intra-macrophage amastigote forms, with an EC₅₀ of 0.46 ± 0.02 µM. The selectivity index demonstrated by curzerene on these parasite forms was 182.32, being respectively 44.15 and 8.47 times more selective than meglumine antimoniate and amphotericin B. The antiamastigote activity of curzerene was associated with immunomodulatory activity, as it increased TNF-α, IL-12, and NO levels, and lysosomal activity, and decreased IL-10 and IL-6 cytokine levels detected in macrophages infected and treated. In conclusion, our results demonstrate that curzerene is an effective and selective antileishmanial agent, a candidate for in vivo investigation in models of antileishmanial activity.

Antileishmanial activity of cordiaquinone E towards Leishmania (Leishmania) amazonensis

Leishmaniasis is caused by several protozoan species of Leishmania, and being endemically present in 98 countries around the world, it is also a severe public-health problem. The available antileishmanial drugs are toxic and yet present risks of recurrent infection. Efforts to find new, effective, and safe oral agents for the treatment of leishmaniasis are continuing throughout the world. This work aimed to evaluate the antileishmania activity of cordiaquinone E (CORe), isolated from the roots of Cordia polycephala (Lam.) I. M. Johnston. Cytotoxicity, and possible mechanisms of action against promastigote and amastigote forms of Leishmania amazonensis were examined. CORe was effective in inhibiting promastigote (IC₅₀ 4.5 ± 0.3 µM) and axenic amastigote (IC₅₀ 2.89 ± 0.11 µM) growth in concentrations found non-toxic for the host cell (CC₅₀ 246.81 ± 14.5 µM). Our results revealed that CORe presents direct activity against the parasite, inducing cell death by apoptosis. CORe present greater activity against intracellular amastigotes (EC₅₀ 1.92 ± 0.2 µM), yet with much higher selectivity indexes than the reference drugs, being respectively more benign towards RAW 264.7 macrophages than meglumine antimoniate and amphotericin B, (respectively by 4.68 and 42.84 fold). The antiamastigote activity was associated with increased TNF-α, IL-12, NO, and ROS levels, as well as decreased IL-10 levels. These results encourage the progression of studies on this compound for the development of new leishmanicidal agents.

Nucleolin overexpression in breast cancer cell sub-populations with different stem-like phenotype enables targeted intracellular delivery of synergistic drug combination

Breast cancer stem cells (CSC) are thought responsible for tumor growth and relapse, metastization and active evasion to standard chemotherapy. The recognition that CSC may originate from non-stem cancer cells (non-SCC) through plastic epithelial-to-mesenchymal transition turned these into relevant cell targets. Of crucial importance for successful therapeutic intervention is the identification of surface receptors overexpressed in both CSC and non-SCC. Cell surface nucleolin has been described as overexpressed in cancer cells as well as a tumor angiogenic marker. Herein we have addressed the questions on whether nucleolin was a common receptor among breast CSC and non-SCC and whether it could be exploited for targeting purposes. Liposomes functionalized with the nucleolin-binding F3 peptide, targeted simultaneously, nucleolin-overexpressing putative breast CSC and non-SCC, which was paralleled by OCT4 and NANOG mRNA levels in cells from triple negative breast cancer (TNBC) origin. In murine embryonic stem cells, both nucleolin mRNA levels and F3 peptide-targeted liposomes cellular association were dependent on the stemness status. An in vivo tumorigenic assay suggested that surface nucleolin overexpression per se, could be associated with the identification of highly tumorigenic TNBC cells. This proposed link between nucleolin expression and the stem-like phenotype in TNBC, enabled 100% cell death mediated by F3 peptide-targeted synergistic drug combination, suggesting the potential to abrogate the plasticity and adaptability associated with CSC and non-SCC. Ultimately, nucleolin-specific therapeutic tools capable of simultaneous debulk multiple cellular compartments of the tumor microenvironment may pave the way towards a specific treatment for TNBC patient care.

Receptor tyrosine kinase Axl is required for resistance of leukemic cells to FLT3-targeted therapy in acute myeloid leukemia

In acute myeloid leukemia (AML), about 25-30% of patients harbor a constitutively active receptor tyrosine kinase (RTK) FLT3 encoded by a FLT3 allele harboring internal tandem duplication (FLT3-ITD) mutation. The presence of FLT3-ITD correlates with poor prognosis in AML and it makes FLT3 an attractive therapeutic target in AML. Unfortunately, to date small-molecule inhibitors of FLT3 have resulted in only partial and transient clinical responses with residual leukemic blasts resistant to FLT3 inhibitors detected in blood or bone marrow. In this study, we investigated whether the RTK Axl is responsible for resistance of FLT3-ITD(+) AML cells to PKC412 and AC220, FLT3 inhibitors currently under clinical trials for FLT3-ITD(+) AML patients. Upon treatment with PKC412 or AC220, phosphorylation of Axl was significantly enhanced in the FLT3-ITD(+) MV4-11 AML cell line and in primary blasts from a FLT3-ITD(+) AML patient. Consistently, a PKC412-resistant AML cell line and PKC412-resistant primary blasts from FLT3-ITD(+) AML patients had significantly higher levels of constitutively phosphorylated Axl and total Axl when compared with a PKC412-sensitive AML cell line and PKC412-sensitive primary blasts from FLT3-ITD(+) AML patients. We also found that resistance of AML cells against the FLT3 inhibitor PKC412 and AC220 was substantially diminished by the inhibition of Axl via a small-molecule inhibitor TP-0903, a soluble receptor Axl fusion protein Axl-Fc or knockdown of Axl gene expression by shRNA. Collectively, our study suggests that Axl is required for resistance of FLT3-ITD(+) AML cells against the FLT3 inhibitor PKC412 and AC220, and that inhibition of Axl activation may overcome resistance to FLT3-targeted therapy in FLT3-ITD(+) AML.

In vitro modulation of Bcl-2 levels in small cell lung cancer cells: effects on cell viability

Small cell lung cancer (SCLC) is an aggressive disease, representing 15% of all cases of lung cancer, has high metastatic potential and low prognosis that urgently demands the development of novel therapeutic approaches. One of the proposed approaches has been the down-regulation of BCL2, with poorly clarified and controversial therapeutic value regarding SCLC. The use of anti-BCL2 small interfering RNA (siRNA) in SCLC has never been reported. The aim of the present study was to select and test the in vitro efficacy of anti-BCL2 siRNA sequences against the protein and mRNA levels of SCLC cells, and their effects on cytotoxicity and chemosensitization. Two anti-BCL2 siRNAs and the anti-BCL2 G3139 oligodeoxynucleotide (ODN) were evaluated in SCLC cells by the simultaneous determination of Bcl-2 and viability using a flow cytometry method recently developed by us in addition to Western blot, real-time reverse-transcription PCR, and cell growth after single and combined treatment with cisplatin. In contrast to previous reports about the use of ODN, a heterogeneous and up to 80% sequence-specific Bcl-2 protein knockdown was observed in the SW2, H2171 and H69 SCLC cell lines, although without significant sequence-specific reduction of cell viability, cell growth, or sensitization to cisplatin. Our results question previous data generated with antisense ODN and supporting the present concept of the therapeutic interest in BCL2 silencing per se in SCLC, and support the growing notion of the necessity of a multitargeting molecular approach for the treatment of cancer.

BH3-only proteins: the death-puppeteer's wires

Most cell death in vertebrates proceeds through the intrinsic pathway of apoptosis and results from unregulated increase of mitochondrial membrane permeability. Bcl2-associated X protein (Bax) and Bcl2-antagonist/killer protein (Bak), the effector proapoptotic members of the Bcl-2 family, are, in their active state, the principal accomplices for this permeabilization process. How exactly Bax and Bak are activated has been a matter of major investigation in the last decade, and suitable tools offered by quantitative cytometric methodologies have significantly contributed to the understanding of the function of Bcl-2 family members. Here, we review the most relevant findings in this field and highlight one common trait that has emerged from the diverse new theories: a crucial role in the control of Bax/Bak activation has to be attributed to the BH3-only subset of the Bcl-2 family. BH3-only proteins exert their proapoptotic activity by hierarchical and tightly tuned interactions with other Bcl-2 family members and operate as sensors of intracellular/extracellular death signals and vectors of information to the core apoptotic machinery. Given their essential role in apoptosis, BH3-only molecules are proposed as molecular targets for the cure of diseases associated with abnormal cell death, as in the case with neurodegenerative conditions. As well, they are explored as possible tools for cancer therapy, according to the concept that molecules mimicking the BH3 domain of these proteins could selectively and efficiently cooperate in the cell killing by chemotherapeutic drugs. A few BH3 mimetics are currently being tested in clinical trials of hematologic and solid tumors. Nevertheless, the knowledge about the cellular and molecular mechanisms that regulate responsiveness to BH3 therapy has to be further expanded and will benefit from recent advances in cytometric quantitative technologies.

Design of peptide-targeted liposomes containing nucleic acids

Anticancer systemic gene silencing therapy has been so far limited by the inexistence of adequate carrier systems that ultimately provide an efficient intracellular delivery into target tumor cells. In this respect, one promising strategy involves the covalent attachment of internalizing-targeting ligands at the extremity of PEG chains grafted onto liposomes. Therefore, the present work aims at designing targeted liposomes containing nucleic acids, with small size, high encapsulation efficiency and able to be actively internalized by SCLC cells, using a hexapeptide (antagonist G) as a targeting ligand. For this purpose, the effect of the liposomal preparation method, loading material (ODN versus siRNA) and peptide-coupling procedure (direct coupling versus post-insertion) on each of the above-mentioned parameters was assessed. Post-insertion of DSPE-PEG-antagonist G conjugates into preformed liposomes herein named as stabilized lipid particles, resulted in targeted vesicles with a mean size of about 130 nm, encapsulation efficiency close to 100%, and a loading capacity of approximately 5 nmol siRNA/mumol of total lipid. In addition, the developed targeted vesicles showed increased internalization in SCLC cells, as well as in other tumor cells and HMEC-1 microvascular endothelial cells. The improved cellular association, however, did not correlate with enhanced downregulation of the target protein (Bcl-2) in SCLC cells. These results indicate that additional improvements need to be performed in the future, namely by ameliorating the access of the nucleic acids to the cytoplasm of the tumor cells following receptor-mediated endocytosis.