Edited by Xiao-Fan Wang Malignant glioma (MG) is the most lethal primary brain tumor. In addition to having inherent resistance to radiation treatment and chemotherapy, MG cells are highly infiltrative, rendering focal therapies ineffective. Genes involved in MG cell migration and glial cell differentiation are up-regulated by hypophosphorylated nuclear factor I (NFI), which is dephosphorylated by the phosphatase calcineurin in MG cells. Calcineurin is cleaved and thereby activated by calpain proteases, which are, in turn, inhibited by calpastatin (CAST). Here, we show that the CAST gene is a target of NFI and has NFI-binding sites in its intron 3 region. We also found that NFI-mediated regulation of CAST depends on NFI's phosphorylation state. We noted that occupation of CAST intron 3 by hypophosphorylated NFI results in increased activation of an alternative promoter. This activation resulted in higher levels of CAST transcript variants, leading to increased levels of CAST protein that lacks the N-terminal XL domain. CAST was primarily present in the cytoplasm of NFI-hypophosphorylated MG cells, with a predominantly perinuclear immunostaining pattern. NFI knockdown in NFI-hypophosphorylated MG cells increased CAST levels at the plasma membrane. These results suggest that NFI plays an integral role in the regulation of CAST variants and CAST subcellular distribution. Along with the previous findings indicating that NFI activity is regulated by calcineurin, these results provide a foundation for further investigations into the possibility of regulatory cross-talk between NFI and the CAST/calpain/calcineurin signaling pathway in MG cells.

Edited by Xiao-Fan Wang Glioblastoma (GBM) is a brain tumor that remains largely incurable because of its highly-infiltrative properties. Nuclear factor I (NFI)-type transcription factors regulate genes associated with GBM cell migration and infiltration. We have previously shown that NFI activity depends on the NFI phosphorylation state and that calcineurin phosphatase dephosphorylates and activates NFI. Calcineurin is cleaved and activated by calpain proteases whose activity is, in turn, regulated by an endogenous inhibitor, calpastatin (CAST). The CAST gene is a target of NFI in GBM cells, with differentially phosphorylated NFIs regulating the levels of CAST transcript variants. Here, we uncovered an NFIB-calpain 1-positive feedback loop mediated through CAST and calcineurin. In NFI-hyperphosphorylated GBM cells, NFIB expression decreased the CAST-to-calpain 1 ratio in the cytoplasm. This reduced ratio increased autolysis and activity of cytoplasmic calpain 1. Conversely, in NFIhypophosphorylated cells, NFIB expression induced differential subcellular compartmentalization of CAST and calpain 1, with CAST localizing primarily to the cytoplasm and calpain 1 to the nucleus. Overall, this altered compartmentalization increased nuclear calpain 1 activity. We also show that nuclear calpain 1, by cleaving and activating calcineurin, induces NFIB dephosphorylation. Of note, knockdown of calpain 1, NFIB, or both increased GBM cell migration and up-regulated the pro-migratory factors fatty acid-binding protein 7 (FABP7) and Ras homolog family member A (RHOA). In summary, our findings reveal bidirectional cross-talk between NFIB and calpain 1 in GBM cells. A physiological consequence of this positive feedback loop appears to be decreased GBM cell migration.

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Suppl 3 -S7 T2 FLAIR sequences. LQ less than 0.3 was considered RN. Result: Twenty-two patients were followed for a median 320 days. Sixteen patients developed radionecrosis in 21 of 62 lesions (33%), four of which were symptomatic (20%). Eleven of these lesions received 3 fractions and ten received one fraction. RN risk increased with increasing tumor volume (log odds ratio=1.12, p=0.04). There was no difference in incidence of RN in patients who received whole brain radiotherapy (WBRT) (p=0.11), hypo-fractionation (p=0.98) or had a higher maximum dose (p=0.71). Radiographic RN, however, did not clear in any patients who developed it. Eight patients developed a local recurrence (12%), six of which occurred in the single fraction group. Conclusion: Radionecrosis was significantly related to tumor volume but not fractionation, WBRT, or maximum dose. Overall, our results indicate patients receiving SRS for multiple brain metastasis have a higher rate of radionecrosis than the literature and poorer survival despite having equivalent local control. Background: The benefits of increasing extent of resection (EOR) for both overall survival and progression-free survival (PFS) in glioblastoma has been well documented. However, models predicting surgical outcomes have failed to incorporate a patient"s IDH status, a known prognostic factor. We isolate the impact of IDH on surgical outcomes. We determine the effect modification of increasing EOR and decreasing residual tumor volume (RTV) on IDH status. Methods: We performed a retrospective cohort study of 98 patients with glioblastoma who had undergone either biopsy or surgical resection. Tumor volumes were determined by volumetric analysis. Univariable and multivariable Cox PH Regression models were built using overall survival and PFS as endpoints. Results: Increasing EOR and decreasing RTV were both associated with prolonged overall survival and PFS. When IDH status was added to multivariable models, the model utilizing RTV provided a slightly better fit compared to EOR. An interaction term between RTV and IDH status was characterized, such that at low RTVs the prognosis of an IDH mutant is significantly better than that of an IDH wild-type, an effect that is less important as RTV increases. The significance of this term was confirmed by improved fit upon insertion into multivariable models. Conclusion: Minimizing RTV and increasing EOR are important prognostic factors for both IDH wild-type and IDH mutant glioblastoma. The protective benefit of the IDH mutation at lower RTVs suggests these patients are the best candidates for aggressive surgical resection. The impact of repeated surgery on survival for patients with recurrent glioblastoma Nassiri F, Badhiwala J, Wang J, Zadeh G. farshad.nassiri@mail.utoronto.ca Background: Recurrent glioblastoma portends a poor prognosis and the role of repeat surgery in improving survival remains uncertain. Therefore, we undertook a systematic review and metaanalysis in order to determine if repeat surgical resection provides a meanin...