Allosteric Inhibition of c-Abl to Induce Unfolded Protein Response and Cell Death in Multiple Myeloma

Familial schwannomatosis carrying LZTR1 variant p.R340X with brain tumor: A case report

Schwannomatosis (SWN) is a rare genetic condition characterized by the risk of developing multiple benign peripheral nerve sheath tumors; however, the risk of developing malignant tumors in patients with SWN remains unclear. This study described the case of a 57-year-old Japanese man diagnosed with SWN whose older brother also had SWN. Whole-exome sequencing identified a heterozygous mutation [c.1018C > T (p.Arg340X)] in the LZTR1 gene, linked to the RAS/MAPK pathway, in the patient and his brother. Moreover, the patient had aphasia and right-sided paralysis because of a brain tumor. RNA sequencing revealed the remarkable upregulation of several genes associated with oxidative stress, such as the reactive oxygen species pathway and oxidative phosphorylation, a downstream effector of the RAS/MAPK pathway, in the the patient and his brother compared with healthy volunteers. The final diagnosis was LZTR1-related familial SWN, and the dysregulated RAS/MAPK pathway in this patient might be associated with brain tumorigenesis.

Profiling of Unfolded Protein Response Markers and Effect of IRE1α-specific Inhibitor in Pituitary Neuroendocrine Tumor

CONTEXT

Inositol-requiring enzyme 1α (IRE1α) and PKR-like ER kinase (PERK), which are endoplasmic reticulum (ER) membrane proteins, regulate the unfolded protein response (UPR). These molecules have recently gained attention as a novel therapeutic target in secretory tumors. The roles of the UPR in pituitary neuroendocrine tumors (PitNETs) are unclear.

OBJECTIVE

To clarify UPR profiling of PitNETs and to investigate the effect of pharmacological modulation of UPR by KIRA8, a newly developed IRE1α-specific inhibitor.

METHODS

In 131 patients with PitNETs, we evaluated RNA expression of UPR markers in PitNETs and their clinical phenotypes. Using GH3 cells, we examined the effects of KIRA8 and its combination with octreotide on UPR profiling, cell growth, and apoptosis.

RESULTS

Cytoprotective adaptive-UPR (A-UPR) markers were more increased in functioning PitNETs (FPitNETs, n = 112) than in nonfunctioning PitNETs (NFPitNETs, n = 19), while there was no difference in proapoptotic terminal-UPR (T-UPR) markers. Similarly, overt somatotroph tumors (STs, acromegaly, n = 11) increased A-UPR compared with silent STs (n = 10). In STs, serum IGF-1 levels were inversely correlated with Txnip mRNA expression, a representative T-UPR marker. KIRA8 inhibited cell growth and facilitated apoptosis in GH3 cells with increased expressions of T-UPR markers, which was enhanced by the combination with octreotide. Octreotide increased mRNA expression of Txnip and Chop, but decreased spliced Xbp1 under ER stress. Octreotide is suggested to inhibit activation of IRE1α but to reciprocally induce T-UPR under PERK.

CONCLUSION

UPR markers in FPitNETs are implicated as dominant A-UPR but blunted T-UPR. KIRA8, enhanced with octreotide, unbalances the UPR, leading to antitumor effects. Targeting IRE1α may provide a novel strategy to treat PitNETs.

Identification of the unfolded protein response pathway as target for radiosensitization in pancreatic cancer

BACKGROUND AND PURPOSE

Due to the high intrinsic radioresistance of pancreatic ductal adenocarcinoma (PDAC), radiotherapy (RT) is only beneficial in 30% of patients. Therefore, this study aimed to identify targets to improve the efficacy of RT in PDAC.

MATERIALS AND METHODS

Alamar Blue proliferation and colony formation assay (CFA) were used to determine the radioresponse of a cohort of 38 murine PDAC cell lines. A gene set enrichment analysis was performed to reveal differentially expressed pathways. CFA, cell cycle distribution, γH2AX FACS analysis, and Caspase 3/7 SYTOX assay were used to examine the effect of a combination treatment using KIRA8 as an IRE1α-inhibitor and Ceapin-A7 as an inhibitor against ATF6.

RESULTS

The unfolded protein response (UPR) was identified as a pathway highly expressed in radioresistant cell lines. Using the IRE1α-inhibitor KIRA8 or the ATF6-inhibitor Ceapin-A7 in combination with radiation, a radiosensitizing effect was observed in radioresistant cell lines, but no substantial alteration of the radioresponse in radiosensitive cell lines. Mechanistically, increased apoptosis by KIRA8 in combination with radiation and a cell cycle arrest in the G1 phase after ATF6 inhibition and radiation have been observed in radioresistant cell lines.

CONCLUSION

So, our data show evidence that the UPR is involved in radioresistance of PDAC. Increased apoptosis and a G1 cell cycle arrest seem to be responsible for the radiosensitizing effect of UPR inhibition. These findings are supportive for developing novel combination treatment concepts in PDAC to overcome radioresistance.