Effects of the Anti-Tumorigenic Agent AT101 on Human Glioblastoma Cells in the Microenvironmental Glioma Stem Cell Niche.

Glioblastoma (GBM) is a barely treatable disease due to its profound chemoresistance. A distinct inter- and intratumoral heterogeneity reflected by specialized microenvironmental niches and different tumor cell subpopulations allows GBMs to evade therapy regimens. Thus, there is an urgent need to develop alternative treatment strategies. A promising candidate for the treatment of GBMs is AT101, the R(-) enantiomer of gossypol. The present study evaluates the effects of AT101, alone or in combination with temozolomide (TMZ), in a microenvironmental glioma stem cell niche model of two GBM cell lines (U251MG and U87MG). AT101 was found to induce strong cytotoxic effects on U251MG and U87MG stem-like cells in comparison to the respective native cells. Moreover, a higher sensitivity against treatment with AT101 was observed upon incubation of native cells with a stem-like cell-conditioned medium. This higher sensitivity was reflected by a specific inhibitory influence on the p-p42/44 signaling pathway. Further, the expression of CXCR7 and the interleukin-6 receptor was significantly regulated upon these stimulatory conditions. Since tumor stem-like cells are known to mediate the development of tumor recurrences and were observed to strongly respond to the AT101 treatment, this might represent a promising approach to prevent the development of GBM recurrences.

Macroscopic Silicone Microchannel Matrix for Tailored Drug Release and Localized Glioblastoma Therapy.

Localized therapy of the highly malignant brain tumor glioblastoma multiforme (GBM) could help to drastically improve the treatment efficiency and increase the patient's median survival. Here, a macroscopic PDMS matrix composed of interconnected microchannels for tailored drug release and localized GBM therapy is introduced. Based on a simple bottom-up fabrication method using a highly versatile sacrificial template, the presented strategy solves the scaling problem associated with the previously developed microchannel-based drug delivery systems, which were limited to two dimensions due to the commonly employed top-down microfabrication methods. Additionally, tailoring of the microchannel density, the fraction of drug-releasing microchannels and the macroscopic size of the drug delivery systems enabled precise adjustment of the drug release kinetics for more than 10 days. As demonstrated in a long-term GBM in vitro model, the release kinetics of the exemplarily chosen GBM drug AT101 could be tailored by variation of the microchannel density and the initial drug concentration, leading to diffusion-controlled AT101 release. Adapting a previously developed GBM treatment plan based on a sequential stimulation with AT101, measured anti-tumorigenic effects of free versus PDMS-released AT101 were comparable in human GBM cells and demonstrated efficient biological activity of PDMS-released AT101.

The intramembrane protease SPPL2c promotes male germ cell development by cleaving phospholamban.

Signal peptide peptidase (SPP) and the four homologous SPP-like (SPPL) proteases constitute a family of intramembrane aspartyl proteases with selectivity for type II-oriented transmembrane segments. Here, we analyse the physiological function of the orphan protease SPPL2c, previously considered to represent a non-expressed pseudogene. We demonstrate proteolytic activity of SPPL2c towards selected tail-anchored proteins. Despite shared ER localisation, SPPL2c and SPP exhibit distinct, though partially overlapping substrate spectra and inhibitory profiles, and are organised in different high molecular weight complexes. Interestingly, SPPL2c is specifically expressed in murine and human testis where it is primarily localised in spermatids. In mice, SPPL2c deficiency leads to a partial loss of elongated spermatids and reduced motility of mature spermatozoa, but preserved fertility. However, matings of male and female SPPL2c-/- mice exhibit reduced litter sizes. Using proteomics we identify the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA2)-regulating protein phospholamban (PLN) as a physiological SPPL2c substrate. Accumulation of PLN correlates with a decrease in intracellular Ca2+ levels in elongated spermatids that likely contribute to the compromised male germ cell differentiation and function of SPPL2c-/- mice.