No abstract

The flavonoid apigenin, extracted from the Brazilian plant Croton betulaster Müll. has demonstrated the ability to inhibit proliferation, induce differentiation, and modify the inflammatory profile of glioma cells. The aim of the present study was to evaluate the effect of apigenin on chemotaxis and regulation of inflammatory cytokines of microglia cells and these impacts on glioma cell growth. In cultures of isolated rat microglia, it was observed that apigenin induced changes in Iba1‐positive cells to an ameboid phenotype, associated to an increase in the expression of the activated M1 profile marker OX‐42 and iNOS and a reduction in the expression of the M2 profile marker CD206. Besides, apigenin modulated the tumor necrosis factor and IL‐10 release by microglia. Treatment of C6 glioma cells with conditioned medium of microglia treated with apigenin‐induced reduction of tumor migration and viability, associated with significant reduction in IL‐6 levels. On the other hand, treatment of C6 cells with apigenin‐induced microglia chemotaxis to glioma in vitro. Moreover, apigenin treatment of microglia/C6 co‐cultures induced preferentially reduction in the viability of C6 cells and increased microglia‐activated phenotype, associated with a change in the balance of TNF/IL‐10 levels. Together, these results demonstrated that the flavonoid apigenin restores the immune profile of microglia against glioma cells.

No abstract

The first‐line chemotherapy treatment for Glioblastoma (GBM) ‐ the most aggressive and frequent brain tumor ‐ is temozolomide (TMZ). The Sonic hedgehog (SHH) pathway is involved with GBM tumorigenesis and TMZ chemoresistance. The role of SHH pathway inhibition in the potentiation of TMZ's effects using T98G, U251, and GBM11 cell lines is investigated herein. The combination of GANT‐61 and TMZ over 72 hr suggested a synergistic effect. All TMZ‐resistant cell lines displayed a significant decrease in cell viability, increased DNA fragmentation and loss of membrane integrity. For T98G cells, G2/M arrest was observed, while U251 cells presented a significant increase in reactive oxygen species production and catalase activity. All the cell lines presented acidic vesicles formation correlated to Beclin‐1 overexpression. The combined treatment also enhanced GLI1 expression, indicating the presence of select resistant cells. The selective inhibition of the SHH pathway potentiated the cytotoxic effect of TMZ, thus becoming a promising in vitro strategy for GBM treatment.

Telomerase is a good target for new anticancer drug development because it is present in over 85% of human tumours. However, despite chronic therapy is a condition for anti-telomerase approach, the effects of long-term treatment with telomerase inhibitors remain not well understood. In this work, it was evaluated the effects of long-term treatment of human MDA-MB-231 breast cancer cells with the telomerase inhibitor MST-312. Cells were treated for 72 hours or 140 days, and it was accessed their viability, proliferation rate, morphology, telomeric DNA content, and resistance mechanism. The drug had a clear short-term effect, including chemosensitizing cells for docetaxel and irinotecan, but the chronic exposition led to selection of long telomeres clones, changing characteristics of original cell line. This effect was confirmed in a clonal culture with homogenous karyotype. MRP-1 expression and alternative lengthening of telomeres (ALT) were discarded as additional mechanisms of resistance. This data suggest that, considering the intra-tumour heterogeneity (ITH), what is already a big challenge for treatment of cancer, chronic exposition to telomerase inhibitors can promote tumour adaptations with potential clinical repercussion, drawing attention to ongoing clinical trials and pointing important considerations most times neglected on studies about use of these inhibitors on cancer therapy.Significance of the study: Antitumour action of telomerase inhibitors is well known, but it depends on a long-term exposition because cells will undergo telomere erosion only after many duplication cycles. Recently, the frustrating results of clinical trials with these inhibitors aroused the interest of the scientific community to understand the mechanisms of resistance to anti-telomerase therapy. In this study, we conducted an 18-week experiment to show that telomerase inhibition can lead to cell adaptations and selection of long-telomeres clones, leading to acquisition of resistance. However, we also showed that this inhibitor can sensitize cells to the chemotherapeutic drugs docetaxel and irinotecan.

Glioblastomas (GBMs) are tumors that have a high ability to migrate, invade and proliferate in the healthy tissue, what greatly impairs their treatment. These characteristics are associated with the complex microenvironment, formed by the perivascular niche, which is also composed of several stromal cells including astrocytes, microglia, fibroblasts, pericytes and endothelial cells, supporting tumor progression. Further microglia and macrophages associated with GBMs infiltrate the tumor. These innate immune cells are meant to participate in tumor surveillance and eradication, but they become compromised by GBM cells and exploited in the process. In this review we discuss the context of the GBM microenvironment together with the actions of flavonoids, which have attracted scientific attention due to their pharmacological properties as possible anti-tumor agents. Flavonoids act on a variety of signaling pathways, counteracting the invasion process. Luteolin and rutin inhibit NFκB activation, reducing IL-6 production. Fisetin promotes tumor apoptosis, while inhibiting ADAM expression, reducing invasion. Naringenin reduces tumor invasion by down-regulating metalloproteinases expression. Apigenin and rutin induce apoptosis in C6 cells increasing TNFα, while decreasing IL-10 production, denoting a shift from the immunosuppressive Th2 to the Th1 profile. Overall, flavonoids should be further exploited for glioma therapy.

These results demonstrate that DHC acts as a chemosensitizing agent selective for glioma cells not affecting non-tumor cells. Considering tumor heterogeneity, DHC demonstrated an anti-cancer potential to activate different cell death pathways. DHC demonstrated could be used for chemotherapy and immunotherapy applications in glioblastomas in the future.

Glioblastoma (GBM) is the most frequent malignant brain tumor. It represents the most aggressive astrocytoma with an overall survival of 14 months. Despite improvements in surgery techniques, radio-and chemotherapy, most patients present treatment resistance, recurrence and disease progression. Therefore, development of effective alternative therapies is essential to overcome treatment failure. The purpose of the study was to evaluate the antitumoral activity of the synthetic compound LQB-118, in vitro. Monolayer and three-dimensional (3D) cell culture systems of human-derived GBM cell lines were used to evaluate the effect of LQB-118 on cell viability, cell death and migration. LQB-118 reduced cell viability as determined by MTT and trypan blue exclusion assays and promoted apoptosis in monolayer cell lines with an intrinsic temozolomide (TMZ)-resistance profile. In 3D culture models, LQB-118 reduced cell viability as evaluated by APH assay and inhibited cell migration while the TMZ resistance profile was maintained. Moreover, LQB-118 reduced p38 and AKT expression and phosphorylation, whereas it reduced only the phosphorylated ERK1/2 form. LQB-118 reduced p38 and NRF2 expression, an axis that is associated with TMZ resistance, revealing a mechanism to overcome resistance. LQB-118 also demonstrated an additional effect when combined with ionizing radiation and cisplatin. In conclusion, the present data demonstrated that LQB-118 maintained its effectiveness in a 3D cell conformation, which shares more similarities with the tumor mass. LQB-118 is a promising agent for GBM treatment as monotherapy and associated with radiotherapy or cisplatin. Its effect is associated with inhibition of GBM-related survival signaling pathways.