Biology subjects

Kim, K.-B.

Publications and source records attributed to Kim, K.-B..

11 recordsLinked to original sources

bioRxiv2023

Robo1 loss has pleiotropic effects on postnatal development and survival

Roundabout guidance receptor 1 (Robo1) is known to function during midbrain development in mice, but its postnatal role remains poorly defined in part due to the perinatal lethality of the mice lacking the gene. Here, we describe the postnatal phenotypes of Robo1-/- mice in the B6/129s genetic background. Robo1-/- mice had both a slower growth rate and shorter lifespan compared to Robo1+/+ littermates. Skin histological analysis revealed that Robo1-/- mice displayed increased wrinkles, enlarged sebaceous glands, and a reduced subcutaneous fat layer. Robo1-/- mice displayed accelerated hair graying in line with an observed overall decrease in melanin production. Although both growth hormone (GH) and insulin-like growth hormone 1 (IGF-1) were suppressed in Robo1-deficient mice at 3 weeks of age, they were expressed at similar levels to Robo1 intact mice at 7 weeks of age. These findings suggest that Robo1-mediated hormone regulation is required for normal growth during the early stages of puberty and may provide a crucial timepoint at which to examine the molecular mechanisms of pituitary disorders.

developmental biology↗

bioRxiv2023

CRACD suppresses neuroendocrinal plasticity of lung adenocarcinoma

Tumor cell plasticity contributes to intratumoral heterogeneity and therapy resistance. Through cell plasticity, lung adenocarcinoma (LUAD) cells transform into neuroendocrinal (NE) tumor cells. However, the mechanisms of NE cell plasticity remain unclear. CRACD, a capping protein inhibitor, is frequently inactivated in cancers. CRACD knock-out (KO) de-represses NE-related gene expression in the pulmonary epithelium and LUAD cells. In LUAD mouse models, Cracd KO increases intratumoral heterogeneity with NE gene expression. Single-cell transcriptomic analysis showed that Cracd KO-induced NE plasticity is associated with cell de-differentiation and activated stemness-related pathways. The single-cell transcriptomes of LUAD patient tumors recapitulate that the distinct LUAD NE cell cluster expressing NE genes is co-enriched with SOX2, OCT4, and NANOG pathway activation, and impaired actin remodeling. This study reveals an unexpected role of CRACD in restricting NE cell plasticity that induces cell de-differentiation, providing new insights into cell plasticity of LUAD.

cancer biology↗

bioRxiv2023

CRACD, a gatekeeper restricting proliferation, heterogeneity, and immune evasion of small cell lung cancer

Small cell lung cancer (SCLC) is aggressive with limited therapeutic options. Despite recent advances in targeted therapies and immunotherapies, therapy resistance is a recurring issue, which might be partly due to tumor cell plasticity, a change in cell fate. Nonetheless, the mechanisms underlying tumor cell plasticity and immune evasion in SCLC remain elusive. CRACD, a capping protein inhibitor that promotes actin polymerization, is frequently inactivated in SCLC. Cracd knockout (KO) transforms preneoplastic cells into SCLC tumor-like cells and promotes in vivo SCLC development driven by Rb1, Trp53, and Rbl2 triple KO. Cracd KO induces neuroendocrine (NE) plasticity and increases tumor cell heterogeneity of SCLC tumor cells via dysregulated NOTCH1 signaling by actin cytoskeleton disruption. CRACD depletion also reduces nuclear actin and induces EZH2-mediated H3K27 methylation. This nuclear event suppresses the MHC-I genes and thereby depletes intratumoral CD8+ T cells for accelerated SCLC tumorigenesis. Pharmacological blockade of EZH2 inhibits CRACD-negative SCLC tumorigenesis by restoring MHC-I expression and immune surveillance. Unsupervised single-cell transcriptomics identifies SCLC patient tumors with concomitant inactivation of CRACD and downregulated MHC-I pathway. This study defines CRACD, an actin regulator, as a tumor suppressor that limits cell plasticity and immune evasion and proposes EZH2 blockade as a viable therapeutic option for CRACD-negative SCLC.

cancer biology↗

bioRxiv2022

Opa1 and Drp1 reciprocally regulate cristae morphology, ETC function, and NAD+ regeneration in KRas-mutant lung adenocarcinoma

Oncogenic KRas activates mitochondrial fission through Erk-mediated phosphorylation of the mitochondrial fission GTPase Drp1. Drp1 deletion inhibits tumorigenesis of KRas-driven pancreatic cancer, but the role of mitochondrial dynamics in other Ras-driven malignancies is poorly defined. Here we demonstrate that in vitro and in vivo growth of KRas-driven lung adenocarcinoma is unaffected by deletion of Drp1, but inhibited by deletion of Opa1, the GTPase that regulates inner membrane fusion and promotes proper cristae morphology. Mechanistically, Opa1 knockout induces loss of electron transport chain (ETC) complex I assembly and activity that inhibits tumor cell proliferation through loss of NAD+ regeneration. Simultaneous inactivation of Drp1 and Opa1 restores cristae morphology, complex I activity and cell proliferation indicating that mitochondrial fission activity drives ETC dysfunction induced by Opa1 knockout. Our results support a model in which mitochondrial fission events disrupt cristae structure and tumor cells with hyperactive fission activity require Opa1 activity to maintain ETC function.

cell biology↗

bioRxiv2022

WNT5A-RHOA axis is a new vulnerability in small-cell lung cancer

WNT signaling presents an attractive target for cancer therapy due to its widespread oncogenic role. However, the molecular players involved in WNT signaling and the impact of their perturbation remain unknown for numerous recalcitrant cancers including small-cell lung cancer (SCLC). Here we show that beta-catenin, a master mediator of canonical WNT signaling, is not required for SCLC development in genetically engineered mouse models (GEMMs) and its transcriptional program is largely silenced during tumor development. Instead, inactivation of p130 in SCLC cells induces expression of WNT5A, a ligand for beta-catenin-independent WNT pathways. WNT5A is both sufficient and required for SCLC development and cell proliferation and selectively induces Rhoa transcription and activates RHOA protein to drive SCLC. Rhoa knockout suppresses SCLC development in vivo, and chemical perturbation of RHOA selectively inhibits SCLC cell proliferation. These findings suggest a novel requirement for the WNT5A-RHOA axis in SCLC that is distinct from other noncanonical WNT pathways. This vulnerability of p130-WNT5A-RHOA pathway provides critical insight into the development of novel therapeutic strategies for the recalcitrant cancer, as well as the stratification of patients who may benefit from them. This study also sheds new light on the heterogeneity of WNT signaling and the molecular determinants of its cell-type specificity.

cancer biology↗

bioRxiv2021

Unique role and vulnerability of EP300 KIX domain in small-cell lung cancer

EP300 (E1A binding protein p300) is a versatile transcription co-activator important in cell proliferation and differentiation. The gene EP300 is frequently mutated in diverse cancer types, including small-cell lung cancer (SCLC). While it is widely believed that these mutations result in loss of EP300 function, the impact on SCLC pathogenesis remains largely unknown. Here we demonstrate that mutant EP300 variants lacking histone acetyltransferase (HAT) domain accelerate tumor development in autochthonous mouse models of SCLC. However, unexpectedly, complete knockout of Ep300 suppresses tumor development and inhibits proliferation of both human and mouse SCLC cells. Genetic dissection of EP300 domains identifies kinase-inducible domain (KID)-interacting (KIX) domain, specifically its interaction with transcription factors such as CREB1 and MYB, as the determinant of pro-tumorigenic activity. Blockade of the KIX-mediated protein interactions using a small molecule and a recombinant peptide mimicking the KIX-binding sequences of EP300-interacting partners inhibits the growth of SCLC cells. These findings identify domain-specific roles of EP300 in SCLC and unique vulnerability of the EP300 KIX domain to potential therapeutics.

cancer biology↗

bioRxiv2020

Role of ischemic preconditioning in cardioprotective mechanisms of mCRP deposited myocardium in a rat model

The deposition of monomeric C-reactive protein (mCRP) in the myocardium aggravates ischemia-reperfusion injury (IRI) and myocardial infarction. Ischemic preconditioning (IPC) is known to protect the myocardium against IRI. We evaluated the effects of IPC on mCRP-deposited myocardium due to IRI in a rat model. Myocardial IRI was produced by ligation of the coronary artery. Direct IPC was applied before IRI using multiple short direct occlusions of the coronary artery. CRP was infused intravenously after IRI. The study groups included the following: sham (n=3), IRI only (n=5), IRI+CRP (n=9), and IPC+IRI+CRP (n=6) groups. The infarct area and area at risk were assessed using Evans blue and 2,3,5-triphenyltetrazolium chloride (2,3,5-TTC) staining. Additionally, mCRP immunostaining and interleukin (IL)-6 mRNA reverse transcriptase-polymerase chain reaction (RT-PCR) were performed. In the IRI+CRP group, the infarcted area, mCRP deposition, and IL-6 mRNA expression were higher than those in the IRI only group. However, in the IPC+IRI+CRP group, the infarction (20% vs. 34% p=0.085) and mCRP myocardial deposition (21% vs. 44%, p=0.026) were lower and IL-6 mRNA expression was higher than those in the IRI+CRP group (fold change, 407 vs. 326, p=0.808), although this was not statistically significant. IPC has cardioprotective effects against myocardial damage caused by mCRP deposition. This protective effect is related to the increase in IL-6 mRNA expression.View Full Text

pathology↗

bioRxiv2020

Fragmentation of Small-cell Lung Cancer Regulatory States in Heterotypic Microenvironments

Small-cell lung cancers derive from pulmonary neuroendocrine cells, which have stemlike properties to reprogram into other cell types upon lung injury. It is difficult to uncouple transcriptional plasticity of these transformed cells from genetic changes that evolve in primary tumors or secondary metastases. Profiling of single cells also problematic if the required sample dissociation activates injury-like signaling and reprogramming. Here, we defined cell-state heterogeneities in situ through laser capture microdissection-based 10-cell transcriptomics coupled with stochastic-profiling fluctuation analysis. Using labeled cells from a small-cell lung cancer mouse model initiated by neuroendocrine deletion of Rb1-Trp53, we profiled variations in transcript abundance to identify cell-to-cell differences in regulatory state in vitro and in vivo. Fluctuating transcripts in spheroid culture were partly shared among Rb1-Trp53-null models, and heterogeneities increased considerably when cells were delivered intravenously to colonize the liver. Colonization of immunocompromised animals drove fractional appearance of alveolar type II-like markers and poised cells for paracrine stimulation from immune cells and hepatocytes. Immunocompetency further exaggerated the fragmentation of tumor states in the liver, yielding mixed stromal signatures evident in bulk sequencing from autochthonous tumors and metastases. Dozens of transcript heterogeneities recur irrespective of biological context; their mapped orthologs brought together observations of murine and human small-cell lung cancer. Candidate heterogeneities recurrent in the liver also stratified primary human tumors into discrete groups not readily explained by molecular subtype but with prognostic relevance. We conclude that heterotypic interactions in the liver and lung are an accelerant for intratumor heterogeneity in small-cell lung cancer. Statement of significanceThe single-cell regulatory heterogeneity of small-cell lung cancer becomes increasingly elaborate in the liver, a common metastatic site for the disease.

cancer biology↗

bioRxiv2020

A trans-eQTL network regulates osteoclast multinucleation and bone mass

Functional characterisation of cell-type specific regulatory networks is key to establish a causal link between genetic variation and phenotype. The osteoclast offers a unique model for interrogating the contribution of co-regulated genes to in vivo phenotype as its multinucleation and resorption activities determine quantifiable skeletal traits. Here we took advantage of a trans-regulated gene network (MMnet, macrophage multinucleation network) which we found to be significantly enriched for GWAS variants associated with bone-related phenotypes. We found that the network hub gene Bcat1 and seven other co-regulated MMnet genes out of 13, regulate bone function. Specifically, global (Pik3cb-/-, Atp8b2+/-, Igsf8-/-, Eml1-/-, Appl2-/-, Deptor-/-) and myeloid-specific Slc40a1{Delta}LysMCre knockout mice displayed abnormal bone phenotypes. We report antagonizing effects of MMnet genes on bone mass in mice and osteoclast multinucleation/resorption in humans with strong correlation between the two. These results identify MMnet as a functionally conserved network that regulates osteoclast fusion and bone mass. Impact statementWe took advantage of the osteoclast whose multinucleation properties correlate with bone mass. We show that a trans-regulated gene network (MMnet) controls skeletal homeostasis through osteoclast multinucleation and function.

cell biology↗

bioRxiv2019

Oncogenic role of FGFR1 and vulnerability of RBL2-FGFR1 axis in small cell lung cancer development

Small cell lung cancer (SCLC) remains a recalcitrant disease; limited therapeutic options have not improved overall survival and approved targeted therapies are lacking. Amplification of the tyrosine kinase receptor FGFR1 (fibroblast growth factor receptor 1) is one of the few actionable alterations found in SCLC genome. However, efforts to develop targeted therapies for FGFR1-amplified SCLC are hindered by critical gaps in knowledge around the molecular origins and mediator of FGFR1-driven signalling and the physiological impact of targeting FGFR1. Here we demonstrate the oncogenic impact of increased FGFR1 on the malignant progression of precancerous cells and the necessity of nonamplified FGFR1 for SCLC development and homeostasis. Unexpected dependency of Rbl2 loss-driven tumor development on FGFR1 in autochthonous mouse models reveals a novel function of p130 (encoded by Rbl2), a member of the RB family of tumor suppressors, as a regulator of FGFR1 expression. Additionally, FGFR1-dependent SCLC cells require activation of PLCG1 for continued growth. Together, this study uncovers mechanisms of FGFR1-driven SCLC that involves p130 upstream and PLCG1 downstream and provides potential biomarkers for anti-FGFR1 therapeutic strategy.

cancer biology↗

bioRxiv2017

KDM2B is a histone H3K79 demethylase and induces transcriptional repression via SIRT1-mediated chromatin silencing

The methylation of histone H3 lysine 79 (H3K79) is an active chromatin marker and is prominant in actively transcribed regions of the genome. However, demethylase of H3K79 remains unknown despite intensive research. Here, we show that KDM2B (also known as FBXL10), a member of the Jumonji C family of proteins and known for its histone H3K36 demethylase activity, is a di- and tri-methyl H3K79 demethylase. We demonstrate that KDM2B induces transcriptional repression of HOXA7 and MEIS1 via occupancy of promoters and demethylation of H3K79. Furthermore, genome-wide analysis suggests that H3K79 methylation levels increase when KDM2B is depleted, indicating that KDM2B functions as an H3K79 demethylase in vivo. Finally, stable KDM2B-knockdown cell lines exhibit displacement of NAD+-dependent deacetylase SIRT1 from chromatin, with concomitant increases in H3K79 methylation and H4K16 acetylation. Our findings identify KDM2B as an H3K79 demethylase and link its function to transcriptional repression via SIRT1-mediated chromatin silencing.

genetics↗