Tumoricidal, Temozolomide- and Radiation-Sensitizing Effects of KCa3.1 K+ Channel Targeting In Vitro Are Dependent on Glioma Cell Line and Stem Cell Fraction

Reportedly, the intermediate-conductance Ca²⁺-activated potassium channel K_Ca3.1 contributes to the invasion of glioma cells into healthy brain tissue and resistance to temozolomide and ionizing radiation. Therefore, K_Ca3.1 has been proposed as a potential target in glioma therapy. The aim of the present study was to assess the variability of the temozolomide- and radiation-sensitizing effects conferred by the K_Ca3.1 blocking agent TRAM-34 between five different glioma cell lines grown as differentiated bulk tumor cells or under glioma stem cell-enriching conditions. As a result, cultures grown under stem cell-enriching conditions exhibited indeed higher abundances of mRNAs encoding for stem cell markers compared to differentiated bulk tumor cultures. In addition, stem cell enrichment was paralleled by an increased resistance to ionizing radiation in three out of the five glioma cell lines tested. Finally, TRAM-34 led to inconsistent results regarding its tumoricidal but also temozolomide- and radiation-sensitizing effects, which were dependent on both cell line and culture condition. In conclusion, these findings underscore the importance of testing new drug interventions in multiple cell lines and different culture conditions to partially mimic the in vivo inter- and intra-tumor heterogeneity.

Peptide Dendrimers with Non-Symmetric Bola Structure Exert Long Term Effect on Glioblastoma and Neuroblastoma Cell Lines

BACKGROUND

Glioblastoma (GBM) is the most common malignant tumor of the central nervous system (CNS). Neuroblastoma (NB) is one of the most common cancers of childhood derived from the neural crest cells. The survival rate for patients with GBM and high-risk NB is poor; therefore, novel therapeutic approaches are needed. Increasing evidence suggests a dual role of redox-active compounds in both tumorigenesis and cancer treatment. Therefore, in this study, polyfunctional peptide-based dendrimeric molecules of the bola structure carrying residues with antiproliferative potential on one side and the antioxidant residues on the other side were designed.

METHODS

We synthesized non-symmetric bola dendrimers and assessed their radical scavenging potency as well as redox capability. The influence of dendrimers on viability of rat primary cerebellar neurons (CGC) and normal human astrocytes (NHA) was determined by propidium iodide staining and cell counting. Cytotoxicity against human GBM cell lines, T98G and LN229, and NB cell line SH-SY5Y was assessed by cell counting and colony forming assay.

RESULTS

Testing of CGC and NHA viability allowed to establish a range of optimal dendrimers structure and concentration for further evaluation of their impact on two human GBM and one human NB cell lines. According to ABTS, DPPH, FRAP, and CUPRAC antioxidant tests, the most toxic for normal cells were dendrimers with high charge and an excess of antioxidant residues (Trp and PABA) on both sides of the bola structure. At 5 μM concentration, most of the tested dendrimers neither reduced rat CGC viability below 50-40%, nor harmed human neurons (NHA). The same dose of compounds 16 or 22, after 30 min treatment decreased the number of SH-SY5Y and LN229 cells, but did not affect the number of T98G cells 48 h post treatment. However, either compound significantly reduced the number of colonies formed by SH-SY5Y, LN229, and T98G cells measured 14 days after treatment.

CONCLUSIONS

Peptide dendrimers with non-symmetric bola structure are excellent scaffolds for design of molecules with pro/antioxidant functionality. Design of molecules with an excess of positive charges and antioxidant residues rendered molecules with high neurotoxicity. Single, 30 min exposition of the GBM and NB cell lines to the selected bola dendrimers significantly suppressed their clonogenic potential.

The autism-related protein CHD8 contributes to the stemness and differentiation of mouse hematopoietic stem cells

Chromodomain helicase DNA-binding protein 8 (CHD8) is an ATP-dependent chromatin-remodeling factor that is encoded by the most frequently mutated gene in individuals with autism spectrum disorder. CHD8 is expressed not only in neural tissues but also in many other organs; however, its functions are largely unknown. Here, we show that CHD8 is highly expressed in and maintains the stemness of hematopoietic stem cells (HSCs). Conditional deletion of Chd8 specifically in mouse bone marrow induces cell cycle arrest, apoptosis, and a differentiation block in HSCs in association with upregulation of the expression of p53 target genes. A colony formation assay and bone marrow transplantation reveal that CHD8 deficiency also compromises the stemness of HSCs. Furthermore, additional ablation of p53 rescues the impaired stem cell function and differentiation block of CHD8-deficient HSCs. Our results thus suggest that the CHD8-p53 axis plays a key role in regulation of the stemness and differentiation of HSCs.

Against Repurposing Methadone for Glioblastoma Therapy

Methadone, which is used as maintenance medication for outpatient treatment of opioid dependence or as an analgesic drug, has been suggested by preclinical in vitro and mouse studies to induce cell death and sensitivity to chemo- or radiotherapy in leukemia, glioblastoma, and carcinoma cells. These data together with episodical public reports on long-term surviving cancer patients who use methadone led to a hype of methadone as an anti-cancer drug in social and public media. However, clinical evidence for a tumoricidal effect of methadone is missing and prospective clinical trials, except in colorectal cancer, are not envisaged because of the limited preclinical data available. The present article reviews the pharmacokinetics, potential molecular targets, as well as the evidence for a tumoricidal effect of methadone in view of the therapeutically achievable doses in the brain. Moreover, it provides original in vitro data showing that methadone at clinically relevant concentrations fails to impair clonogenicity or radioresistance of glioblastoma cells.

Intratumor Heterogeneity and Therapy Resistance: Contributions of Dormancy, Apoptosis Reversal (Anastasis) and Cell Fusion to Disease Recurrence

A major challenge in treating cancer is posed by intratumor heterogeneity, with different sub-populations of cancer cells within the same tumor exhibiting therapy resistance through different biological processes. These include therapy-induced dormancy (durable proliferation arrest through, e.g., polyploidy, multinucleation, or senescence), apoptosis reversal (anastasis), and cell fusion. Unfortunately, such responses are often overlooked or misinterpreted as “death” in commonly used preclinical assays, including the in vitro colony-forming assay and multiwell plate “viability” or “cytotoxicity” assays. Although these assays predominantly determine the ability of a test agent to convert dangerous (proliferating) cancer cells to potentially even more dangerous (dormant) cancer cells, the results are often assumed to reflect loss of cancer cell viability (death). In this article we briefly discuss the dark sides of dormancy, apoptosis, and cell fusion in cancer therapy, and underscore the danger of relying on short-term preclinical assays that generate population-based data averaged over a large number of cells. Unveiling the molecular events that underlie intratumor heterogeneity together with more appropriate experimental design and data interpretation will hopefully lead to clinically relevant strategies for treating recurrent/metastatic disease, which remains a major global health issue despite extensive research over the past half century.

Bromelain Inhibitory Effect on Colony Formation: An In vitro Study on Human AGS, PC3, and MCF7 Cancer Cells

Bromelain is dotted with anticancer properties on various cancer cell lines. Anticancer pathways of bromelain, as well related intervening signalization are under investigation. Investigating the inhibitory potential of bromelain on AGS, PC3, and MCF7 cells proliferation and colony formation. The bromelain inhibitory potential on AGS, PC3, and MCF7 cells proliferation at various bromelain concentrations was assessed by MTT; thereby, bromelain potency on colony formation impediment was evaluated using clonogenic assays at determined 50% inhibitory concentrations (IC₅₀) on four different cell densities (10, 50, 100, and 200 cells per well). Bromelain inhibits AGS, PC3, and MCF7 cells proliferation in such a dose-dependent manner. Determined IC₅₀ to AGS, PC3, and MCF7 cells were 65, 60 and 65μg/ml respectively. At IC₅₀, bromelain significantly suppressed the AGS, PC3, and MCF7 cells colony formation at four treated densities (10, 50, 100 and 200 cells per well). Plating efficiency percentage and cell surviving fraction were decreased after bromelain treatment to AGS, PC3, and MCF7 human cancer cells as a function of initial cell density. The 50, 50 or 100, and 10 or 50 cells per well were considered to be optimum number of initial cell density for AGS, PC3, and MCF7 cells. Cell proliferative and colony formation inhibition are two pathways to in vitro bromelain anticancer effects. The current study displayed a dose-dependent inhibitory effect of bromelain, as well impeding colony formation AGS, PC3, and MCF7 human cancer cells.

Microcolony Size Distribution Assay Enables High-Throughput Cell Survival Quantitation

Cell survival is a critical and ubiquitous endpoint in biology. The broadly accepted colony formation assay (CFA) directly measures a cell's ability to divide; however, it takes weeks to perform and is incompatible with high-throughput screening (HTS) technologies. Here, we describe the MicroColonyChip, which exploits microwell array technology to create an array of colonies. Unlike the CFA, where visible colonies are counted by eye, using fluorescence microscopy, microcolonies can be analyzed in days rather than weeks. Using automated analysis of microcolony size distributions, the MicroColonyChip achieves comparable sensitivity to the CFA (and greater sensitivity than the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide [XTT] assay). Compared to CellTiter-Glo, the MicroColonyChip is as sensitive and also robust to artifacts caused by differences in initial cell seeding density. We demonstrate efficacy via studies of radiosensitivity and chemosensitivity and show that the approach is amenable to multiplexing. We conclude that the MicroColonyChip is a rapid and automated alternative for cell survival quantitation.

Paeoniflorin suppresses pancreatic cancer cell growth by upregulating HTRA3 expression

Paeoniflorin (PF) is an active monoterpene glycoside extracted from Paeonia lactiflora Pall. PF has exhibited antitumor effects in various cancer types. However, the effects of PF in pancreatic cancer are largely unexplored. Here, we showed that PF suppressed growth of pancreatic cancer cell lines Capan-1 and MIAPaCa-2 and profoundly sensitized these cells to X-ray irradiation. Through microarray analysis, we identified HTRA3, a tumor-suppressor candidate gene, as the most increased gene upon PF treatment in Capan-1 cells. Ectopic expression of HTRA3 led to reduced cell proliferation and increased expression of apoptotic protein Bax, suggesting a tumor suppressive role of HTRA3 in pancreatic cancer cells. Together, our results provide a set group of genetic proofs and biological proofs that PF inhibited pancreatic cancer growth by upregulating HTRA3.

Mimicking the lipid peroxidation inhibitory activity of phospholipid hydroperoxide glutathione peroxidase (GPx4) by using fatty acid conjugates of a water-soluble selenolane

A series of fatty acid conjugates of trans-3,4-dihydroxy-1-selenolane (DHS) were synthesized by reacting DHS with appropriate acid chlorides. The obtained monoesters were evaluated for their antioxidant capacities by the lipid peroxidation assay using a lecithin/cholesterol liposome as a model system. The observed antioxidant capacities against accumulation of the lipid hydroperoxide (LOOH) increased with increasing the alkyl chain length and became saturated for dodecanoic acid (C₁₂) or higher fatty acid monoesters, for which the capacities were much greater than those of DHS, its tridecanoic acid (C₁₃) diester, and PhSeSePh. On the other hand, the bacteriostatic activity of myristic acid (C₁₄) monoester, evaluated through the colony formation assay using Bacillus subtilis, indicated that it has higher affinity to bacterial cell membranes than parent DHS. Since DHS-fatty acid conjugates would inhibit lipid peroxidation through glutathione peroxidase (GPx)-like 2e⁻ mechanism, higher fatty acid monoesters of DHS can mimic the function of GPx4, which interacts with LOOH to reduce it to harmless alcohol (LOH). Importance of the balance between hydrophilicity and lipophilicity for the design of effective GPx4 mimics was suggested.