f PALB2/FANCN is mutated in breast and pancreatic cancers and Fanconi anemia (FA). It controls the intranuclear localization, stability, and DNA repair function of BRCA2 and links BRCA1 and BRCA2 in DNA homologous recombination repair and breast cancer suppression. Here, we show that PALB2 directly interacts with KEAP1, an oxidative stress sensor that binds and represses the master antioxidant transcription factor NRF2. PALB2 shares with NRF2 a highly conserved ETGE-type KEAP1 binding motif and can effectively compete with NRF2 for KEAP1 binding. PALB2 promotes NRF2 accumulation and function in the nucleus and lowers the cellular reactive oxygen species (ROS) level. In addition, PALB2 also regulates the rate of NRF2 export from the nucleus following induction. Our findings identify PALB2 as a regulator of cellular redox homeostasis and provide a new link between oxidative stress and the development of cancer and FA.T he two major high-penetrance breast cancer susceptibility genes BRCA1 and BRCA2 encode very large proteins with a critical function in homologous recombinational repair (HRR) of DNA double-strand breaks (15). PALB2 was discovered as a major BRCA2 binding partner that controls its intranuclear localization, stability, recombinational repair, and DNA damage checkpoint functions (38). Immediately after its discovery, germ line truncating mutations in PALB2 were identified in familial breast cancer (4,22,31) and the N subtype of Fanconi anemia (FA-N) (23, 37). Later, PALB2 was also found to be mutated in familial pancreatic cancer, being the second most highly mutated pancreatic susceptibility gene after BRCA2 (7,25). Furthermore, hypermethylation of the PALB2 promoter occurs in a significant fraction (ϳ7%) of both sporadic and familial breast/ovarian cancer cases (21). To date, dozens of truncating PALB2 mutations have been identified in cancer families around the world, causing moderate to very high risks of breast cancer (1,26,30). Finally, certain single nucleotide polymorphisms (SNPs) in the gene have been suggested to confer an increased risk of breast cancer (2).The PALB2 protein contains a coiled-coil domain at the N terminus and a series of WD repeats at its C terminus (Fig. 1A). The WD repeats together form a ␤-propeller structure that directly binds BRCA2 (18), and the N-terminal coiled-coil motif was later found to directly bind BRCA1 (28,41,42). Approximately 50% of PALB2 and 50% of BRCA2 are associated with each other in the cell with high affinity (28, 38). The stoichiometry of PALB2-BRCA1 binding appears to be much lower (28, 42). However, the interaction has proved crucial for HRR as several mutations generated in each protein that abrogate the interaction have been shown to greatly compromise repair efficiency (28,41,42). Furthermore, multiple naturally occurring, patient-derived missense variants that disrupt PALB2 binding have been identified in both BRCA1 and BRCA2, and all of them have been found to abrogate HRR (28, 38). Thus, PALB2 links BRCA1 and BRCA2 in HRR and breast cancer s...

Glioblastoma (GBM) is the most frequent and lethal brain cancer. The lack of early detection methods, the presence of rapidly growing tumor cells and the high levels of recurrence due to chemo- and radio-resistance make this cancer an extremely difficult disease to treat. Emerging studies have focused on inhibiting AKT activation; here we demonstrate that in primary GBM tumor samples, full-dose inhibition of AKT activity leads to differential responses among samples in the context of cell death and self- renewal, reinforcing the notion that GBM is a heterogeneous disease. In contrast, low-dose AKT inhibition when combined with fractionation of radiation doses leads to a significant apoptosis-mediated cell death of primary patient-derived GBM cells. Therefore, low-dose targeted therapies might be better for radiosensitization of primary GBM cells and further allow for reducing the clinical toxicities often associated with targeting the AKT/PI3K/mTOR pathway. This work emphasizes the discrepancies between cell lines and primary tumors in drug testing, and indicates that there are salient differences between patients, highlighting the need for personalized medicine in treating high-grade glioma.

Autophagy inhibition by CQ increases CRC cell sensitivity to concurrent treatment with 5-FU and RT in vitro, suggesting that addition of CQ to chemoRT improves CRC treatment response.

Purpose High-grade gliomas are lethal malignancies that cause morbidity and mortality due to local progression rather than metastatic spread. Our group has previously demonstrated that human GRM1 (hGRM1) is ectopically expressed in melanocytes leading to a transformed phenotype. Riluzole, a glutamate release inhibitor, leads to apoptotic cell death via DNA damage. Recent work has demonstrated the pathological significance of the related mGluR3/GRM3 (protein or gene: hGRM3) in gliomas. We evaluated the effect of riluzole on glioma cells. Experimental Design Western blot analysis and immunofluorescence was performed to assess for GRM3 expression in commercially available and patient-derived glioma cells and for functional analysis of GRM3 using receptor agonist/antagonists and downstream effectors, ERK and AKT phosphorylation, as the read-out. Glutamate secretion by glioma cells was measured using ELISA. Flank and intracranial mouse xenograft models were used to assess growth delay with the glutamate release inhibitor, riluzole (RIL). Immunofluorescence was used to evaluate 53BP1 or γ-H2AX foci after RIL. Results GRM3 was expressed in most tested glioma samples, and strongly expressed in some. Glioma cells were found to secrete glutamate in the extracellular space and to respond to receptor stimulation by activating downstream ERK. This signaling was abrogated by pretreatment with RIL. Treatment with RIL caused an increase in DNA damage markers, and an increase in cellular cytotoxicity in vitro and in vivo . Conclusions We have demonstrated that pretreatment with the glutamate-release inhibitor riluzole sensitizes glioma cells to radiation and leads to greater cytotoxicity; these results have clinical implications for patients with glioblastoma.