Biology subjects

VanSaun, M.

Publications and source records attributed to VanSaun, M..

6 recordsLinked to original sources

bioRxiv2025

Non-Contrast microCT Analysis of Obese Adipose in Response to Cold-Exposure Reveals Sex-Specific Alterations

In 2020, it was reported that obesity in the United States had increased by 12% from 1999 to 2018. While exercise and diet are optimal lifestyle modifications to curb obesity, drug-based therapeutics focus on glucagon-like peptide (GLP) modifiers. Alternatively, current research suggests that a specialized type of adipose, called thermogenic adipose, may help protect against obesity. Active thermogenic adipose can metabolize free fatty acids (FFAs) and carbohydrates to carry out non-shivering thermogenesis (NST), potentially providing a method for reducing excess energy stores. While brown adipose tissue (BAT) provides the primary thermogenic response, we hypothesized that exposing diet-induced obese (DIO) mice to colder temperatures would also diminish white adipose tissue (WAT) depots and suppress their inflammatory signature. To measure adipose response to cold in vivo, we applied a non-contrast microCT ({micro}CT) imaging analysis. Male and female mice were housed at thermoneutrality (TN) and fed a Western-style diet (WD) ad lib until they became obese. Once they reached this stage, the mice were subjected to a thermalshift (TS) and exposed to either room temperature (RT) of 22{degrees}C or a colder temperature of 18{degrees}C. The adipose response was then assessed in post-exposure tissues by histological analysis, proteomics, and molecular characterization to correlate phenotypic changes with our {micro}CT findings. Results from this analysis revealed a sex-specific response to cold exposure: thermogenic adipose was predominantly formed in the interscapular BAT (iBAT) of male mice, while female mice showed formation in their perigonadal WAT (pgWAT) and iBAT when exposed to 18{degrees}C. Furthermore, male mice exhibited a decline in serum glucose levels when subjected to 18{degrees}C, which was increased in TS female mice. Serum-free fatty acids (FFAs) were unaffected by either sex across different environmental conditions. Importantly, using a mass-spectrometry-based approach, we detected a reduction in pro-inflammatory cytokines in the conditioned media (CM) of pgWAT and iBAT from TS male mice compared to TN DIO male mice. Overall, our studies demonstrated a new {micro}CT-based analytical method to detect changes in obese adipose tissue and highlighted unique sex-specific responses to environmental exposure. Our findings suggest that thermogenic adipose may offer a promising avenue for combating obesity and reducing its pathologic characteristics.

cell biology↗

bioRxiv2024

DUSP6 is upregulated in metastasis and influences migration and metabolism in pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy characterized by KRAS mutations in approximately 95% of cases. Despite recent advancements with KRAS inhibitors, therapeutic resistance has emerged, and combination approaches are needed. In particular, it is important to understand how downstream signaling of KRAS supports PDAC growth. For example, DUSP6, a dual-specificity phosphatase that modulates ERK1/2 phosphorylation and RAS pathway activity, has emerged as an important regulator of KRAS-MAPK signaling. Transcriptomic analyses demonstrate that DUSP6 is markedly overexpressed in PDAC tumors compared to non-tumoral pancreatic tissue. Single-cell RNA-seq reveals its upregulation in epithelial tumor cells, with further elevation in metastatic lesions relative to primary tumors. This upregulation correlates with the quasi-mesenchymal/squamous molecular subtype, and clinically, high DUSP6 expression is associated with poorer overall survival. Gene set enrichment analyses of metastatic samples indicate that DUSP6 is linked to pathways involved in cell migration and metabolism. To elucidate DUSP6s functional roles, stable knockdown of DUSP6 in PDAC cell lines resulted in increased ERK/MAPK activation and altered migratory capacity. Metabolic profiling showed enhanced basal glycolysis following DUSP6 suppression. However, combined inhibition of glycolysis and DUSP6 downregulation did not affect the migratory phenotype, indicating that glycolytic alterations do not drive migration. These findings highlight the dual and independent roles of DUSP6 in modulating migratory capacity and glycolysis in PDAC. This study underscores the significance of DUSP6 as a potential therapeutic target and provides new insights into its contributions to PDAC progression. SIGNIFICANCE STATEMENTDUSP6 plays dual and independent roles in pancreatic cancer, regulating both migration and glycolysis. Its upregulation in metastasis is associated with poor prognosis and more aggressive phenotypes, highlighting its clinical relevance. Targeting DUSP6 represents a potential therapeutic strategy to disrupt KRAS-MAPK signaling and target key pathways driving PDAC progression.

cancer biology↗

bioRxiv2024

CREB activation drives acinar to ductal reprogramming and promote pancreatic cancer progression in animal models of alcoholic chronic pancreatitis

BACKGROUND & AIMSChronic alcoholism often leads to pancreatitis, which exacerbates pancreatic damage through acinar cell injury, fibrotic inflammation and activates AKT/mTOR/cyclic adenosine monophosphate response element binding protein 1 (CREB) signaling axis. However, the molecular interplay between oncogenic KrasG12D/+(Kras*) and CREB in promoting pancreatic cancer progression under chronic inflammation remains poorly understood. METHODSExperimental alcoholic chronic pancreatitis (ACP) induction was established in multiple mouse models, with euthanasia during the recovery stage to evaluate tumor latency. CREB was selectively deleted (Crebfl/fl) in Ptf1aCreERTM/+;LSL-KrasG12D/+(KC) genetic mouse models (KCC-/-). Pancreata from Ptf1aCreERTM/+, KC, and KCC-/- mice were analyzed using histological profiling, western blotting, phosphokinase array, and quantitative PCR. Single-cell RNA sequencing was performed in ACP-induced KC mice. Lineage tracing analysis in YFP reporter mice and acinar cell explant cultures analysis were also conducted. RESULTSACP induction in KC mice significantly impaired pancreas repair mechanism. Acinar cell-derived ductal lesions demonstrated sustained CREB hyperactivation in acinar-to-ductal metaplasia (ADM)/pancreatic intraepithelial neoplasia (PanIN) lesions associated with pancreatitis and pancreatic cancer. Persistent CREB activity reprogrammed acinar cells, and increased profibrotic inflammation. Notably, acinar specific Creb deletion in ACP induced models suppressed high grade PanIN development, restrained tumor progression, and improved acinar cell function. CONCLUSIONSOur findings demonstrate that CREB and Kras* promote irreversible ADM, accelerating pancreatic cancer progression with ACP. Targeting CREB may present a promising strategy to mitigate inflammation-driven pancreatic tumorigenesis.

cancer biology↗

bioRxiv2023

Combined PI3K and MAPK inhibition synergizes to suppress PDAC

Oncogenic KRAS mutations are nearly ubiquitous in pancreatic ductal adenocarcinoma (PDAC), yet therapeutic attempts to target KRAS as well as its target MAPK pathway effectors have shown limited success due to the difficulty to pharmacologically target KRAS, inherent drug resistance in PDAC cells, and acquired resistance through activation of alternative mitogenic pathways such JAK-STAT and PI3K-AKT. While KRAS canonically drives the MAPK signaling pathway via RAF-MEK-ERK, it is also known to play a role in PI3K-AKT signaling. Our therapeutic study targeted the PI3K-AKT pathway with the drug Omipalisib (p110/{beta}/{delta}/{gamma} and mTORC1/2 inhibitor) in combination with MAPK pathway targeting drug Trametinib (MEK1/2 inhibitor) or SHP099-HCL (SHP099), which is an inhibitor of the KRAS effector SHP2. Western blot analysis demonstrated that application of Trametinib or SHP099 alone selectively blocked ERK phosphorylation (pERK) but failed to suppress phosphorylated AKT (pAKT) and in some instances increased pAKT levels. Conversely, Omipalisib alone successfully inhibited pAKT but failed to suppress pERK. Therefore, we hypothesized that a combination therapeutic comprised of Omipalisib with either Trametinib or SHP099 would inhibit two prominent mitogenic pathways, MEK and PI3K-AKT, to more effectively suppress pancreatic cancer. In vitro studies demonstrated that both Omipalisib/Trametinib and Omipalisib/SHP099 combination therapeutic strategies were generally more effective than treatment with each drug individually at reducing proliferation, colony formation, and cell migration compared to vehicle controls. Additionally, we found that while combination Omipalisib/SHP099 treatment reduced implanted tumor growth in vivo, the Omipalisib/Trametinib treatment was significantly more effective. Therefore, we additionally tested the Omipalisib/Trametinib combination therapeutic in the highly aggressive PKT (Ptf1acre, LSL-KrasG12D, TGFbR2fl/fl) spontaneous mouse model of PDAC. We subsequently found that PKT mice treated with the Omipalisib/Trametinib combination therapeutic survived significantly longer than mice treated with either drug alone, and more than doubled the mean survival time of vehicle control mice. Altogether, our data support the importance of a dual treatment strategy targeting both MAPK and PI3K-AKT pathways.

cancer biology↗

bioRxiv2023

Adipose contributes to CXCL5 regulated immune evasion in pancreatic cancer

BackgroundCXCR1/2 inhibitors are being implemented with immunotherapies in PDAC clinical trials. Cytokines responsible for stimulating these receptors include CXCL ligands, typically secreted by activated immune cells, fibroblasts, and even adipocytes. Obesity has been linked to poor patient outcome and altered anti-tumor immunity. Adipose-derived cytokines and chemokines have been implicated as potential drivers of tumor cell immune evasion, suggesting a possibility of susceptibility to targeting specifically in the context of obesity. MethodsRNA-sequencing of human PDAC cell lines was used to assess differential influences on the cancer cell transcriptome after treatment with conditioned media from peri-pancreatic adipose tissue of lean and obese PDAC patients. The adipose-induced secretome of PDAC cells was then assessed by cytokine arrays and ELISAs. Lentiviral transduction and CRISPR-Cas9 was used to knock out CXCL5 from a murine PDAC cell line for orthotopic tumor studies in diet-induced obese, syngeneic mice. Flow cytometry was used to define the immune profiles of tumors. Anti-PD-1 immune checkpoint blockade therapy was administered to alleviate T cell exhaustion and invoke an immune response, while the mice were monitored at endpoint for differences in tumor size. ResultsThe chemokine CXCL5 was secreted in response to stimulation of PDAC cells with human adipose conditioned media (hAT-CM). PDAC CXCL5 secretion was induced by either IL-1{beta} or TNF, but neutralization of both was required to limit secretion. Ablation of CXCL5 from tumors promoted an immune phenotype susceptible to PD-1 inhibitor therapy. While application of anti-PD-1 treatment to control tumors failed to alter tumor growth, knockout CXCL5 tumors were diminished. ConclusionsIn summary, our findings show that known adipokines TNF and IL-1{beta} can stimulate CXCL5 release from PDAC cells in vitro. In vivo, CXCL5 depletion alone is sufficient to promote T cell infiltration into tumors in an obese setting, but requires checkpoint blockade inhibition to alleviate tumor burden. DATA AVAILABILITY STATEMENTRaw and processed RNAseq data will be further described in the GEO accession database (awaiting approval from GEO for PRJ number). Additional raw data is included in the supplemental material and available upon reasonable request. WHAT IS ALREADY KNOWN ON THIS TOPICObesity is linked to a worsened patient outcome and immunogenic tumor profile in PDAC. CXCR1/2 inhibitors have begun to be implemented in combination with immune checkpoint blockade therapies to promote T cell infiltration under the premise of targeting the myeloid rich TME. WHAT THIS STUDY ADDSUsing in vitro/ex vivo cell and tissue culture-based assays with in vivo mouse models we have identified that adipose derived IL-1{beta} and TNF can promote tumor secretion of CXCL5 which acts as a critical deterrent to CD8 T cell tumor infiltration, but loss of CXCL5 also leads to a more immune suppressive myeloid profile. HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE, OR POLICYThis study highlights a mechanism and emphasizes the efficacy of single CXCR1/2 ligand targeting that could be beneficial to overcoming tumor immune-evasion even in the obese PDAC patient population.

cancer biology↗

bioRxiv2021

Combined MEK and STAT3 inhibition reprograms the tumor microenvironment to overcome immunotherapy resistance in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is characterized by immune exclusion, pro-inflammatory polarization of cancer-associated fibroblasts (CAF), and resistance to immune checkpoint inhibition (ICI). We have previously demonstrated that reciprocally activated RAS/MEK/ERK and JAK/STAT3 pathways mediate therapeutic resistance, while combined MEK and STAT3 inhibition (MEKi+STAT3i) overcomes such resistance in preclinical models. We now show that combined MEKi+STAT3i not only alters stromal architecture but also uncovers stromal plasticity by revealing a substantial attenuation of Il6/Cxcl1-expressing secretory and Lrrc15-expressing myofibroblastic CAF phenotypes with a concomitant enrichment of Ly6a/Cd34-expressing CAF phenotypes exhibiting mesenchymal progenitor-like properties via single-cell RNA sequencing in Ptf1acre/+;LSL-KrasG12D/+;Tgfbr2flox/flox(PKT) mice. This remodeling of CAF heterogeneity is associated with reprogramming of immunosuppressive myeloid populations and enhanced trafficking of CD8+ T-cells which exhibit a distinct effector transcriptional program. These MEKi+STAT3i-mediated repercussions are in part CAF-dependent, since CRISPR/Cas9 genetic silencing of CAF-restricted Mek1/Stat3 mitigates inflammatory CAF polarization and myeloid infiltration in vivo. Addition of MEKi+STAT3i to PD-1 blockade overcomes ICI resistance by significantly augmenting anti-tumor responses and dramatically improving survival in PKT mice compared with anti-PD-1 monotherapy. The addition of MEKi+STAT3i to PD-1 blockade not only augments the recruitment of activated and memory T-cell populations, but also improves their degranulating capacity and functional cytotoxicity compared to PD-1 blockade alone. Importantly, treatment of a patient with chemotherapy-refractory metastatic PDAC with MEKi (Trametinib), STAT3i (Ruxolitinib), and PD-1 inhibitor (Nivolumab) was well-tolerated and yielded clinical benefit. These data uncover a novel paradigm in which combined MEKi+STAT3i reprograms stromal inflammation and immune tolerance to overcome immunotherapy resistance in PDAC.

cancer biology↗