Ectopic expression of DOCK8 regulates lysosome-mediated pancreatic tumor cell invasion

Amplified lysosome activity is a hallmark of pancreatic ductal adenocarcinoma (PDAC) orchestrated by oncogenic KRAS that mediates tumor growth and metastasis, though the mechanisms underlying this phenomenon remain unclear. Using comparative proteomics, we found that oncogenic KRAS significantly enriches levels of the guanine nucleotide exchange factor (GEF) dedicator of cytokinesis 8 (DOCK8) on lysosomes. Surprisingly, DOCK8 is aberrantly expressed in a subset of PDAC, where it promotes cell invasion in vitro and in vivo. DOCK8 associates with lysosomes and regulates lysosomal morphology and motility, with loss of DOCK8 leading to increased lysosome size. DOCK8 promotes actin polymerization at the surface of lysosomes while also increasing the proteolytic activity of the lysosomal protease cathepsin B. Critically, depletion of DOCK8 significantly reduces cathepsin-dependent extracellular matrix degradation and impairs the invasive capacity of PDAC cells. These findings implicate ectopic expression of DOCK8 as a key driver of KRAS-driven lysosomal regulation and invasion in pancreatic cancer cells.

Inflammation, Infiltration, and Evasion-Tumor Promotion in the Aging Breast

Breast cancer is a significant cause of morbidity and mortality in women, with over two million new cases reported worldwide each year, the majority of which occur in post-menopausal women. Despite advances in early detection and treatment, approximately one-third of patients diagnosed with breast cancer will develop metastatic disease. The pathogenesis and progression of breast cancer are influenced by a variety of biological and social risk factors, including age, ethnicity, pregnancy status, diet, and genomic alterations. Recent advancements in breast cancer research have focused on harnessing the power of the patient's adaptive and innate immune systems for diagnostic and therapeutic purposes. The breast immune microenvironment plays a critical role in regulating tissue homeostasis and resistance to tumorigenesis. In this review, we explore the dynamic changes in the breast immune microenvironment that occur with age, how these changes impact breast cancer development and progression, and how targeted therapeutic interventions that leverage the immune system can be used to improve patient outcomes. Our review emphasizes the importance of understanding the complex interplay between aging, the immune system, and breast cancer, and highlights the potential of immune-based therapies in the fight against this devastating disease.

ATP Synthase c-Subunit Leak Causes Aberrant Cellular Metabolism in Fragile X Syndrome

Loss of the gene (Fmr1) encoding Fragile X mental retardation protein (FMRP) causes increased mRNA translation and aberrant synaptic development. We find neurons of the Fmr1^-/y mouse have a mitochondrial inner membrane leak contributing to a "leak metabolism." In human Fragile X syndrome (FXS) fibroblasts and in Fmr1^-/y mouse neurons, closure of the ATP synthase leak channel by mild depletion of its c-subunit or pharmacological inhibition normalizes stimulus-induced and constitutive mRNA translation rate, decreases lactate and key glycolytic and tricarboxylic acid (TCA) cycle enzyme levels, and triggers synapse maturation. FMRP regulates leak closure in wild-type (WT), but not FX synapses, by stimulus-dependent ATP synthase β subunit translation; this increases the ratio of ATP synthase enzyme to its c-subunit, enhancing ATP production efficiency and synaptic growth. In contrast, in FXS, inability to close developmental c-subunit leak prevents stimulus-dependent synaptic maturation. Therefore, ATP synthase c-subunit leak closure encourages development and attenuates autistic behaviors.

Abstract 4162: Prevalence of germline mutations and variants of uncertain significance (VUS) among Hispanics with suspected hereditary colorectal cancer syndromes

Background: Colorectal cancer (CRC) is one of the leading causes of cancer death in Puerto Rico (PR) and U.S. Approximately 5-10% of all CRC cases are due to hereditary CRC syndromes. Some of the most common hereditary colorectal cancer syndromes include: Familial Adenomatous Polyposis (APC), Lynch Syndrome (MLH1, MSH2, MSH6, PMS2) and MUTYCH (MYH). Germline genetic testing is the gold standard for diagnosing these syndromes. The implications of obtaining a Variant of Uncertain Significance (VUS) in germline genetic testing results remains a clinical challenge especially among minority Hispanic populations. The aim of this project was to determine the prevalence of germline pathogenic mutations and VUS in CRC-risk genes; as well as the phenotype of Hispanic patients with suspected Hereditary CRC syndromes.

Methods: Germline genetic testing from patients with suspected hereditary CRC syndromes seen at the UPR Cancer Genetic Clinic during the period of 2015-2018 were evaluated. Sociodemographics, clinical, tumor and genetic testing data were accessed through the subject’s medical record. Descriptive statistics and frequency distribution tables were generated with the subject’s sociodemographic and clinical information, as well as germline genetic testing results.

Results: A total of 91 patients (61.5% female; mean age 51 years) with suspected hereditary CRC syndromes were tested for germline mutations in relevant CRC-risk genes. The most common malignancies reported were CRC (80%) and endometrial cancer (12%). The majority of patients (n=60) did not have germline mutations in hereditary CRC-risk genes. Mutations in CRC-risk genes were detected in 22% of patients (50% MYH, 45% MMR, 5% APC), while VUSs were detected in 12% (18% MYH, 45% MMR, 36% APC). There were no statistically significant differences with regards to gender, age, personal history of cancer or 1st degree family history of cancer across study groups. All patients with VUSs in MMR-genes had microsatellite stable tumors; while those with mutations in MMR-genes had microsatellite unstable tumors.

Conclusions: VUSs were present in a high-percentage of the patients evaluated for hereditary CRC syndromes. Furthermore, there were no phenotypical differences between patients with pathogenic mutations and those with VUSs. This presents a clinical challenge as non-European populations including Hispanics have genetic variances, which may in fact carry an increase risk for cancer. Future research is warranted to examine the significance and/or reclassify VUSs to improve assessment of genetic test results in admixed populations.

Citation Format: Julyann Perez-Mayoral, Nicole Cruz-Reyes, Andrea Rosa-Vazquez, Maria Gonzalez-Pons, Marcia Cruz-Correa. Prevalence of germline mutations and variants of uncertain significance (VUS) among Hispanics with suspected hereditary colorectal cancer syndromes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4162.

Adenosine A1-Dopamine D1 Receptor Heteromers Control the Excitability of the Spinal Motoneuron

While the role of the ascending dopaminergic system in brain function and dysfunction has been a subject of extensive research, the role of the descending dopaminergic system in spinal cord function and dysfunction is just beginning to be understood. Adenosine plays a key role in the inhibitory control of the ascending dopaminergic system, largely dependent on functional complexes of specific subtypes of adenosine and dopamine receptors. Combining a selective destabilizing peptide strategy with a proximity ligation assay and patch-clamp electrophysiology in slices from male mouse lumbar spinal cord, the present study demonstrates the existence of adenosine A₁-dopamine D₁ receptor heteromers in the spinal motoneuron by which adenosine tonically inhibits D₁ receptor-mediated signaling. A₁-D₁ receptor heteromers play a significant control of the motoneuron excitability, represent main targets for the excitatory effects of caffeine in the spinal cord and can constitute new targets for the pharmacological therapy after spinal cord injury, motor aging-associated disorders and restless legs syndrome.