The Trends and Outcomes of Initial Palliative Chemotherapy in Patients with Pancreatic Cancer in Korea Based on National Health Insurance Service Data.

Background/Objectives: The survival rate of patients with pancreatic cancer (PC) has improved gradually since the introduction of FOLFIRINOX (FFX) and gemcitabine + albumin-bound paclitaxel (GnP) regimens. However, the trends and outcomes of initial palliative chemotherapy before and after the advent of these regimens and their contribution to survival rates are not well understood. This study aimed to investigate this in patients with PC in Korea using claims data from the National Health Insurance Service (NHIS). Methods: Patients diagnosed with PC who underwent initial palliative chemotherapy between 2007 and 2019 were identified from the NHIS database. Patient demographics, comorbidities, chemotherapy regimens, and survival rates were analyzed using follow-up data up to 2020. Results: In total, 14,760 patients (mean age, 63.78 ± 10.18 years; men, 59.19%) were enrolled. As initial palliative chemotherapy, 3823 patients (25.90%) received gemcitabine alone; 2779 (18.83%) received gemcitabine + erlotinib; 1948 (13.20%) received FFX; and 1767 (11.97%) received GnP. The median survival values were 15.00 months for FFX; 11.04 months for GnP; 8.40 months for gemcitabine alone; and 8.51 months for gemcitabine + erlotinib. The adjusted hazard ratio (aHR) for GnP vs. FFX was 1.291 (95% CI, 1.206-1.383) in the multivariate Cox regression analysis of mortality. Radiation therapy (aHR, 0.667; 95% CI, 0.612-0.728) and second-line chemotherapy (aHR, 0.639; 95% CI, 0.597-0.684) were significantly associated with improved survival. Conclusions: Our study found that first-line chemotherapy with FFX was associated with significantly longer survival than the other regimens, although caution is needed in interpreting the results.

Uncoupling of Protein Aggregation and Neurodegeneration in a Mouse Amyotrophic Lateral Sclerosis Model.

Aberrant accumulation of protein aggregates is a pathological hallmark of many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Although a buildup of protein aggregates frequently leads to cell death, whether it is the key pathogenic factor in driving neurodegenerative disease remains controversial. HDAC6, a cytosolic ubiquitin-binding deacetylase, has emerged as an important regulator of ubiquitin-dependent quality control autophagy, a lysosome-dependent degradative system responsible for the disposal of misfolded protein aggregates and damaged organelles. Here, we show that in cell models HDAC6 plays a protective role against multiple disease-associated and aggregation-prone cytosolic proteins by facilitating their degradation. We further show that HDAC6 is required for efficient localization of lysosomes to protein aggregates, indicating that lysosome targeting to autophagic substrates is regulated. Supporting a critical role of HDAC6 in protein aggregate disposal in vivo, genetic ablation of HDAC6 in a transgenic SOD1G93A mouse, a model of ALS, leads to dramatic accumulation of ubiquitinated SOD1G93A protein aggregates. Surprisingly, despite a robust buildup of SOD1G93A aggregates, deletion of HDAC6 only moderately modified the motor phenotypes. These findings indicate that SOD1G93A aggregation is not the only determining factor to drive neurodegeneration in ALS, and that HDAC6 likely modulates neurodegeneration through additional mechanisms beyond protein aggregate clearance.

HDAC6 maintains mitochondrial connectivity under hypoxic stress by suppressing MARCH5/MITOL dependent MFN2 degradation.

Mitochondria undergo fusion and fission in response to various metabolic stresses. Growing evidences have suggested that the morphological change of mitochondria by fusion and fission plays a critical role in protecting mitochondria from metabolic stresses. Here, we showed that hypoxia treatment could induce interaction between HDAC6 and MFN2, thus protecting mitochondrial connectivity. Mechanistically, we demonstrated that a mitochondrial ubiquitin ligase MARCH5/MITOL was responsible for hypoxia-induced MFN2 degradation in HDAC6 deficient cells. Notably, genetic abolition of HDAC6 in amyotrophic lateral sclerosis model mice showed MFN2 degradation with MARCH5 induction. Our results indicate that HDAC6 is a critical regulator of MFN2 degradation by MARCH5, thus protecting mitochondrial connectivity from hypoxic stress.

MFN1 deacetylation activates adaptive mitochondrial fusion and protects metabolically challenged mitochondria.

Fasting and glucose shortage activate a metabolic switch that shifts more energy production to mitochondria. This metabolic adaptation ensures energy supply, but also elevates the risk of mitochondrial oxidative damage. Here, we present evidence that metabolically challenged mitochondria undergo active fusion to suppress oxidative stress. In response to glucose starvation, mitofusin 1 (MFN1) becomes associated with the protein deacetylase HDAC6. This interaction leads to MFN1 deacetylation and activation, promoting mitochondrial fusion. Deficiency in HDAC6 or MFN1 prevents mitochondrial fusion induced by glucose deprivation. Unexpectedly, failure to undergo fusion does not acutely affect mitochondrial adaptive energy production; instead, it causes excessive production of mitochondrial reactive oxygen species and oxidative damage, a defect suppressed by an acetylation-resistant MFN1 mutant. In mice subjected to fasting, skeletal muscle mitochondria undergo dramatic fusion. Remarkably, fasting-induced mitochondrial fusion is abrogated in HDAC6-knockout mice, resulting in extensive mitochondrial degeneration. These findings show that adaptive mitochondrial fusion protects metabolically challenged mitochondria.