Topotecan in combination with radiotherapy in unresectable glioblastoma: a phase 2 study

Controlling the release rate of topotecan from PLGA spheres and increasing its cytotoxicity towards glioblastoma cells by co-loading with calcium chloride

It has been suggested that local administration of topotecan (TT) could increase its efficacy in the treatment of glioblastoma. In this context, a PLGA implant model in the form of spheres with a porous core and stiff surface, loaded with TT and CaCl₂ was developed. An array of formulations differing from each other by the type of PLGA used, the integrity of the surface, the concentrations of TT and CaCl₂ added during the preparation, and the volume of water in the PLGA mix, was prepared, screened and explored by computerized multifactorial analysis. This analysis enabled the simultaneous identification of the most influential experimental factors on the experimental responses, which were pre-determined as the efficiency of TT loading and the TT % cumulative release at 14 days. The multifactorial analysis also revealed how the interactions among the experimental factors affect the performance of the various formulations. Thus, TT concentration and its factorial interaction with the concentration of CaCl₂ added during the spheres' preparation were identified as most prominent on the loading efficiency, while the surface integrity (intact or punctured) and CaCl₂ amount in the spheres were identified as most prominent on the TT % cumulative release from the spheres. TT was found to be cytotoxic towards glioblastoma U87 MG cells, an activity which was enhanced, synergistically, in the presence of CaCl₂ (the relative viability was reduced from 36 to 28% with combination indices of 1.0, 0.37, 0.13 and 0.06 for EC₅₀, EC₇₅, EC₉₀ and EC₉₅, respectively). Interestingly, dividing the TT dose into 3 equal portions, replenished daily to the incubation medium, increased TT cytotoxicity. The relative viability was then reduced from 35 to 7% and in the presence of CaCl₂ - from 28 to 1.9%, suggesting that a local, slow input of TT could be effective in the treatment of glioblastoma by an adjacent TT implant. The increased effect of CaCl₂ on cytotoxicity was also observed when it was co-loaded into the TT spheres. In that case, the cells' viability was reduced from 72 to 27%. It is suggested that the PLGA spheres could be used for tunable local delivery of TT in post-resection adjuvant therapy of glioblastoma.

Drug Repositioning Screen on a New Primary Cell Line Identifies Potent Therapeutics for Glioblastoma

Glioblastoma is a malignant brain cancer with limited treatment options and high mortality rate. While established glioblastoma cell line models provide valuable information, they ultimately lose most primary characteristics of tumors under long-term serum culture conditions. Therefore, established cell lines do not necessarily recapitulate genetic and morphological characteristics of real tumors. In this study, in line with the growing interest in using primary cell line models derived from patient tissue, we generated a primary glioblastoma cell line, KUGBM8 and characterized its genetic alterations, long term growth ability, tumor formation capacity and its response to Temozolomide, the front-line chemotherapy utilized clinically. In addition, we performed a drug repurposing screen on the KUGBM8 cell line to identify FDA-approved agents that can be incorporated into glioblastoma treatment regimen and identified Topotecan as a lead drug among 1,200 drugs. We showed Topotecan can induce cell death in KUGBM8 and other primary cell lines and cooperate with Temozolomide in low dosage combinations. Together, our study provides a new primary cell line model that can be suitable for both in vitro and in vivo studies and suggests that Topotecan can offer promise as a therapeutic approach for glioblastoma.

Convection Enhanced Delivery of Topotecan for Gliomas: A Single-Center Experience

A key limitation to glioma treatment involves the blood brain barrier (BBB). Convection enhanced delivery (CED) is a technique that uses a catheter placed directly into the brain parenchyma to infuse treatments using a pressure gradient. In this manuscript, we describe the physical principles behind CED along with the common pitfalls and methods for optimizing convection. Finally, we highlight our institutional experience using topotecan CED for the treatment of malignant glioma.

Intertumoral heterogeneity in patient-specific drug sensitivities in treatment-naïve glioblastoma

Background

A major barrier to effective treatment of glioblastoma (GBM) is the large intertumoral heterogeneity at the genetic and cellular level. In early phase clinical trials, patient heterogeneity in response to therapy is commonly observed; however, how tumor heterogeneity is reflected in individual drug sensitivities in the treatment-naïve glioblastoma stem cells (GSC) is unclear.

Methods

We cultured 12 patient-derived primary GBMs as tumorspheres and validated tumor stem cell properties by functional assays. Using automated high-throughput screening (HTS), we evaluated sensitivity to 461 anticancer drugs in a collection covering most FDA-approved anticancer drugs and investigational compounds with a broad range of molecular targets. Statistical analyses were performed using one-way ANOVA and Spearman correlation.

Results

Although tumor stem cell properties were confirmed in GSC cultures, their in vitro and in vivo morphology and behavior displayed considerable tumor-to-tumor variability. Drug screening revealed significant differences in the sensitivity to anticancer drugs (p < 0.0001). The patient-specific vulnerabilities to anticancer drugs displayed a heterogeneous pattern. They represented a variety of mechanistic drug classes, including apoptotic modulators, conventional chemotherapies, and inhibitors of histone deacetylases, heat shock proteins, proteasomes and different kinases. However, the individual GSC cultures displayed high biological consistency in drug sensitivity patterns within a class of drugs. An independent laboratory confirmed individual drug responses.

Conclusions

This study demonstrates that patient-derived and treatment-naïve GSC cultures maintain patient-specific traits and display intertumoral heterogeneity in drug sensitivity to anticancer drugs. The heterogeneity in patient-specific drug responses highlights the difficulty in applying targeted treatment strategies at the population level to GBM patients. However, HTS can be applied to uncover patient-specific drug sensitivities for functional precision medicine.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5861-4) contains supplementary material, which is available to authorized users.

Topotecan is a potent inhibitor of SUMOylation in glioblastoma multiforme and alters both cellular replication and metabolic programming

Protein SUMOylation is a dynamic post-translational modification shown to be involved in a diverse set of physiologic processes throughout the cell. SUMOylation has also been shown to play a role in the pathobiology of myriad cancers, one of which is glioblastoma multiforme (GBM). As such, the clinical significance and therapeutic utility offered via the selective control of global SUMOylation is readily apparent. There are, however, relatively few known/effective inhibitors of global SUMO-conjugation. Herein we describe the identification of topotecan as a novel inhibitor of global SUMOylation. We also provide evidence that inhibition of SUMOylation by topotecan is associated with reduced levels of CDK6 and HIF-1α, as well as pronounced changes in cell cycle progression and cellular metabolism, thereby highlighting its putative role as an adjuvant therapy in defined GBM patient populations.

Genotoxic Damage to Glioblastoma Cells Treated with 6 MV X-Radiation in The Presence or Absence of Methoxy Estradiol, IUDR or Topotecan

Objective

To explore the cumulative genotoxic damage to glioblastoma (GBM) cells, grown as multicellular spheroids, following exposure to 6 MV X-rays (2 Gy, 22 Gy) with or without, 2- methoxy estradiol (2ME2), iododeoxyuridine (IUDR) or topotecan (TPT), using the Picogreen assay.

Materials and Methods

The U87MG cells cultured as spheroids were treated with 6 MV X-ray using linear accelerator. Specimens were divided into five groups and irradiated using X-ray giving the dose of 2 Gy after sequentially incubated with one of the following three drug combinations: TPT, 2-ME2/TPT, IUDR/TPT or 2ME2/IUDR/ TPT. One specimen was used as the irradiated only sample (R). The last group was also irradiated with total dose of 22 Gy (each time 2 Gy) of 6 MV X-ray in 11 fractions and treated for three times. DNA damage was evaluated using the Picogreen method in the experimental study.

Results

R/TPT treated group had more DNA damage [double strand break (DSB)/single strand break (SSB)] compared with the untreated group (P<0.05). Moreover the R/ TPT group treated with 2ME2 followed by IUDR had maximum DNA damage in spheroid GBM indicating an augmented genotoxicity in the cells. The DNA damage was induced after seven fractionated irradiation and two sequential treatments with 2ME2/IUDR/TPT. To ensure accuracy of the slope of dose response curve the fractionated radiation was calculated as 7.36 Gy with respect to α/β ratio based on biologically effective dose (BED) formulae.

Conclusion

Cells treated with 2ME2/IUDR showed more sensitivity to radiation and accumulative DNA damage. DNA damage was significantly increased when GBM cells treated with TPT ceased at S phase due to the inhibition of topoisomerase enzyme and phosphorylation of Chk1 enzyme. These results suggest that R/TPT- treated cells increase sensitivity to 2ME2 and IUDR especially when they are used together. Therefore, due to an increase in the level of DNA damage (SSB vs. DSB) and impairment of DNA repair machinery, more cell death will occur. This in turn may improve the treatment of GBM.

Effect of p53 activity on the sensitivity of human glioblastoma cells to PARP-1 inhibitor in combination with topoisomerase I inhibitor or radiation

Poly (ADP-Ribose) polymerase-1 (PARP-1) is involved in the DNA repairing system by sensing and signaling the presence of DNA damage. Inhibition of PARP-1 is tested in combination with DNA damaging agents such as topoisomerase I inhibitors or ionizing radiations (RT) for the treatment of glioblastoma (GBM). Disruption of p53, widely prevalent in GBMs, plays a major role in DNA repairing system. The current study investigates whether p53 activity has an effect on the sensitivity of human GBM cells to PARP-1 inhibitors in combination with topoisomerase I inhibitor topotecan (TPT) and/or RT. Human GBM cell lines carrying a different functional status of p53 were treated with PARP-1 inhibitor NU1025, in combination with TPT and/or RT. Cytotoxic effects were examined by analyzing the antiproliferative activity, the cell cycle perturbations, and the DNA damage induced by combined treatments. PARP inhibition enhanced the antiproliferative activity, the cell cycle perturbations and the DNA damage induced by both TPT or RT in GBM cells. These effects were influenced by the p53 activity: cells carrying an active p53 were more sensitive to the combination of PARP inhibitor and RT, while cells carrying an inactive p53 displayed a higher sensitivity to the combination of PARP inhibitor and TPT. Our study suggests that p53 activity influences the differential sensitivity of GBM cells to combined treatments of TPT, RT, and PARP inhibitors. © 2014 International Society for Advancement of Cytometry.