Increased PD-L1 expression in radioresistant HNSCC cell lines after irradiation affects cell proliferation due to inactivation of GSK-3beta

At present, targeting PD-1/PD-L1 axis for immune checkpoint inhibition has improved treatment of various tumor entities, including head and neck squamous cell carcinoma (HNSCC). However, one part of the patient cohort still shows little improvement or even hyperprogression. We established three radioresistant (RR) and three radiosensitive (RS) HNSCC cell lines. RR cells showed prolonged survival as well as delayed and diminished apoptosis after irradiation with vimentin expression but no E-cadherin expression, whereas RS cell lines died early and exhibited early apoptosis after irradiation and high vimentin expression. Here, we present results demonstrating differential basal PD-L1 gene and protein expression in RR and RS HNSCC cell lines. Moreover, we observed a radiation dose dependent increase of total PD-L1 protein expression in RR cell lines up to 96h after irradiation compared to non-irradiated (non-IRR) cells. We found a significant GSK-3beta phosphorylation, resulting in an inactivation, after irradiation of RR cell lines. Co-immunoprecipitation experiments revealed decreased interaction of GSK-3beta with PD-L1 in non-IRR compared to irradiated (IRR) RR cells leading to PD-L1 stabilization in RR cells. PD-L1 knockdown in RR cells showed a strong decrease in cell survival. In summary, our results suggest an irradiation dependent increase in basal PD-L1 expression in RR HNSCC cell lines via GSK-3beta inactivation

Functional diversity of marine ecosystems after the Late Permian mass extinction event

Article can be accessed from http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2079.htmlThe Late Permian mass extinction event was the most severe such crisis of the past 500 million years and occurred during an episode of global warming. It is assumed to have had significant ecological impact, but its effects on marine ecosystem functioning are unknown and the patterns of marine recovery are debated. We analysed the fossil occurrences of all known Permian-Triassic benthic marine genera and assigned each to a functional group based on their inferred life habit. We show that despite the selective extinction of 62-74% of marine genera there was no significant loss of functional diversity at the global scale, and only one novel mode of life originated in the extinction aftermath. Early Triassic marine ecosystems were not as ecologically depauperate as widely assumed, which explains the absence of a Cambrian-style Triassic radiation in higher taxa. Functional diversity was, however, significantly reduced in particular regions and habitats, such as tropical reefs, and at these scales recovery varied spatially and temporally, probably driven by migration of surviving groups. Marine ecosystems did not return to their pre-extinction state, however, and radiation of previously subordinate groups such as motile, epifaunal grazers led to greater functional evenness by the Middle Triassic

A silicified Early Triassic marine assemblage from Svalbard

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Cycling CD34 expression in subpopulations of head and neck squamous cell carcinoma cell lines is involved in radioresistance and change in cytokeratin expression profile

The expression of the hair follicle stem cell marker CD34 was analyzed in five different head and neck squamous cell carcinoma (HNSCC) cell lines with different antibodies. All HNSCC cell lines expressed CD34 on their cell surface. After cell cycle synchronization via serum starvation, we observed cyclic CD34 expression in HNSCC cells dependent on cell cycle progression via immunofluorescent staining and flow cytometric analysis. Investigation of the CD34(+) and CD34(-) HNSCC populations revealed most of the cells in S-phase and G2/M-Phase in CD34(+) cells in contrast to CD34(-) cells. Knockdown of CD34 in HNSCC cells led to diminished clonal expansion in a colony forming assay after subjecting the cells to ionizing radiation. Furthermore, knockdown of CD34 after cell cycle synchronization induced high CK1, CK4, and CK5 gene expression and downregulation of CK10 gene expression as shown by Taqman(A (R)) quantitative PCR analysis. The expression levels of CK1 and CK10 were verified via western blot analysis. In summary, our study shows that CD34 plays a role during cell cycle progression of head and neck squamous cell carcinoma and additionally is involved in irradiation resistance and differentiation of malignant oral keratinocytes