Important differences were found in the gut microbiota of preterm infants who develop NEC/LOS. The relationship of these changes to current practices in neonatal intensive care requires further exploration.

Cathepsins S (CatS) has been implicated in numerous tumourigenic processes and here we document for the first time its involvement in CCL2 regulation within the tumour microenvironment. Analysis of syngeneic tumours highlighted reduced infiltrating macrophages in CatS depleted tumours. Interrogation of tumours and serum revealed genetic ablation of CatS leads to the depletion of several pro-inflammatory chemokines, most notably, CCL2. This observation was validated in vitro, where shRNA depletion of CatS resulted in reduced CCL2 expression. This regulation is transcriptionally mediated, as evident from RT-PCR analysis and CCL2 promoter studies. We revealed that CatS regulation of CCL2 is modulated through CD74 (also known as the invariant chain), a known substrate of CatS and a mediator of NFkB activity. Furthermore, CatS and CCL2 show a strong clinical correlation in brain, breast and colon tumours. In summary, these results highlight a novel mechanism by which CatS controls CCL2, which may present a useful pharmacodynamic marker for CatS inhibition.

CD74 is a rapidly internalised transmembrane protein, highly expressed in a number of cancers and is associated with increased proliferation and invasion of tumourigenic cells. CD74 is an attractive biomarker to monitor tumour progression and predict overall survival as expression levels have shown to be increased on the cell surface. Recent studies have suggested CD74 plays a potential role in tumour cell response to treatment, showing direct correlation between expression and response. The overall survival of patients with glioblastoma is poor, as treatment options are limited and not well defined. The standard options for the majority of patients is a combination of surgical resection, radiation and chemotherapy. The aim of this study is to investigate the association between CD74 expression and response to radiation and chemotherapy. A panel of glioblastoma cells lines were analysed by RT-PCR and western blotting to examine CD74 expression. Results indicated LN229 and U87MG cells expressed CD74 and using two independent shRNA constructs, CD74 expression was successfully knocked-down in both these lines to enable further study. Interrogation of these CD74-depleted lines indicated a significant reduction in proliferation and migration compared to a non-targeting control. When exposed to increasing doses of radiation the survival fraction of CD74 deficient cells was greater than that of the non-targeting control, suggesting an association between CD74 expression and sensitivity to radiation therapy in glioblastoma cell lines. However, when cells were exposed to increasing doses of Temozolomide there was a decrease in survival fraction of CD74-depleted cells compared to non-targeting controls, which showed no response to treatment. This study aims to further investigate the mechanism by which these change in sensitivity to treatment are mediated and determine if CD74 could not only be used as a marker for tumour progression, but to determine the most appropriate treatment option for patients. Citation Format: Sinead Magorrian, Jonathan Coulter, Tom Flannery, Christopher Scott, Roberta Burden. CD74: a potential mediator of resistance in the treatment of Glioblastoma. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr A40.