Citations

Cancer cachexia, and its associated complications, represent a large and currently untreatable roadblock to effective cancer management. Many potential therapies have been proposed and tested—including appetite stimulants, targeted cytokine blockers, and nutritional supplementation—yet highly effective therapies are lacking. Innovative approaches to treating cancer cachexia are needed. Members of the Kruppel-like factor (KLF) family play wide-ranging and important roles in the development, maintenance, and metabolism of skeletal muscle. Within the KLF family, we identified KLF10 upregulation in a multitude of wasting contexts—including in pancreatic, lung, and colon cancer mouse models as well as in human patients. We subsequently interrogated loss-of-function of KLF10 as a potential strategy to mitigate cancer associated muscle wasting. In vivo studies leveraging orthotopic implantation of pancreas cancer cells into wild-type and KLF10 KO mice revealed significant preservation of lean mass and robust suppression of pro-atrophy muscle-specific ubiquitin ligases Trim63 and Fbxo32, as well as other factors implicated in atrophy, calcium signaling, and autophagy. Bioinformatics analyses identified Transforming growth factor beta (TGF-β), a known inducer of KLF10 and cachexia promoting factor, as a key upstream regulator of KLF10. We provide direct in vivo evidence that KLF10 KO mice are resistant to the atrophic effects of TGF-β. ChIP-based binding studies demonstrated direct binding to Trim63 , a known wasting-associated atrogene. Taken together, we report a critical role for the TGF-β/KLF10 axis in the etiology of pancreatic cancer–associated muscle wasting and highlight the utility of targeting KLF10 as a strategy to prevent muscle wasting and limit cancer-associated cachexia.

Abstract Introduction: Immune checkpoint blockade (ICB) has clinical activity in triple negative breast cancer (TNBC) but is less effective in the ER+HER2- signature, where there is a cold immune microenvironment (IM) and regulatory T cells (Tregs) may suppress effector T cells. Agents that activate the IM by turning cold tumors hot may support ICB. The biguanides hexyl-benzyl-biguanide (HBB) and its bioisostere hexyl-(cuban-1-yl-methyl)-biguanide (HCB) are candidate agents to activate the IM because they potently inhibit biosynthesis of immunosuppressive epoxyeicosatrienoic acids (EETs) and EET-driven oxidative phosphorylation (OXPHOS), while blocking N-glycosylation of immune checkpoint (IC) proteins. We hypothesized that reversal of hypoxia by biguanides in the ovarian dependent ER+HER2- STAT1 KO SSM2ucd mouse mammary carcinoma (MC) model would suppress Tregs and promote effector T cells in the tumor IM. While the SSM2ucd model did not express immune checkpoint protein PD-L1 (B7-H1), it did express related IC proteins B7-H3 and B7-H4. We hypothesized that by inhibiting OXPHOS and reducing N-glycosylation of immune checkpoint proteins, HBB and HCB may promote efficacy of ICB. We chose the SSM2ucd model to test impact of HCB on the ER+ MC IM. Results: SSM2ucd cells exhibited longer tumor latency (60 days) than the basal 4T1 (10 days) and 67NR (20 days) mouse MC models. SSM2ucd tumor reimplantation shortened latency by more than half, to 20 days. Immunohistochemistry showed that B7-H3 and B7-H4 protein levels were 1.2 (P=0.001) and 1.3-fold (P=0.04) higher in reimplanted tumors vs. control. In SSM2ucd cells, HCB inhibited N-glycosylation of B7-H3 (P=0.01) by 35% and B7-H4 (P=0.02) by 45% and suppressed TGFβ induction of B7-H3 by 21% (P=0.02) and B7-H4 by 79% (P=0.001) at 24 hours, while 14,15-EET promoted N-glycosylation of B7-H3 (1.2-fold; P=0.03) and B7-H4 (1.3-fold; P=0.04) at 4 hours. Effects of HBB and HCB on anti-CD3 and anti-CD28 stimulated mouse splenocytes were assayed. The proliferative effects of HBB on CD4+ and CD8+ cells peaked at 12 uM (p<0.001) and for HCB at 6.25 uM (p<0.001). Tregs decreased with HCB at a threshold of 12 uM (p <0.001) and with HBB at 25 uM (P < 0.001) while 14,15-EET increased Tregs (1.2 fold; P=0.02) and suppressed the CD8+:Treg ratio (0.79; P=0.02). In the SSM2ucd mammary allograft model, although HCB 12mg/kg daily did not inhibit tumor growth, it reduced intratumoral hypoxia by 20% (P=0.01), increased CD8+ TIL by 4.4-fold (P=0.04), decreased Treg:CD4+ TIL ratio by 76% (P=0.02), and decreased Treg:CD8+ TIL ratio by 88% (P=0.01) relative to control. Conclusion: B7-H3 and B7-H4 expression inversely correlated with latency of ER+ MC and may represent targets for immune checkpoint antibodies and their drug conjugates. HCB, an inhibitor of OXPHOS and EET biosynthesis, reduced intratumoral hypoxia, increased CD8+ TIL and reduced the Treg:CD8+ ratio, potentially supporting ICB therapy of ER+ MC by turning cold tumors hot. Supported by CDMRP BCRP Grant BC180596, Award Number W81XWH-19-1-0099 Citation Format: Zhijun Guo, Jianxun Lei, Hrishi Venkatesh, David Owen, Adam Bass, Christine Cannon, Joshua McCarra, Brenda Koniar, Craig Flory, Beverly Norris, Robert J. Schumacher, Swaathi Jayaraman, John Hawse, Emmanuel S. Antonarakis, Emanuel F. Petricoin, Julia Wulfkuhle, Robert D. Cardiff, Elizabeth A. Ambrose, Gunda I. Georg, Kaylee L. Schwertfeger, Michael A. Farrar, Brad St. Croix, Matthew P. Goetz, David A. Potter. Hexyl-(cuban-1-yl-methyl)-biguanide (HCB) suppresses N-glycosylation of immune checkpoint proteins B7-H3 and B7-H4, reverses tumor hypoxia, decreases intratumoral regulatory T cells, and increases intratumoral CD8+ T cells in the ovarian dependent ER+HER2- SSM2ucd mammary cancer allograft model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB102.

Abstract Background: Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer-related death among women worldwide. Triple negative breast cancer (TNBC) represents 15-20% of all breast cancers and is an aggressive subtype. Chemotherapy-based treatments remain the standard of care for TNBC. Unfortunately, chemotherapy resistance is common, and for these patients, outcomes are poor and alternative treatment strategies remain an unmet need. circRNAs are a newly identified class of noncoding RNA molecules with covalently closed circular structures. An increasing number of recent studies including ours have indicated that circRNAs play crucial roles in regulating tumor development and chemoresistance. However, the role of circRNAs in the process of chemotherapy resistance and TNBC progression is not clear. Materials and Methods: As a first step towards identifying circRNAs that participate in the development of chemoresistance in TNBC cells, and to determine if targeting such circRNAs is a novel and efficacious therapeutic strategy, doxorubicin-resistant (Doxo-R), paclitaxel-resistant (PTX-R), and double-resistant (DP-R) cell lines were generated from MDA-MB-231. Human circRNA microarrays were utilized to profile the expression of approximately 14,000 known circRNAs in normal breast tissue, matched patient-derived xenografts (PDX) generated prior to and following neoadjuvant chemotherapy (NAC), and TNBC chemosensitive and chemoresistant cell lines. Top hits were validated using RT-PCR. Results: circRNA microarray profiling identified 429 and 310 transcripts differentially expressed in doxorubicin and paclitaxel resistant cells, respectively, compared to parental chemosensitive cell lines (|FC| ≥ 1.5; p value < 0.05). In comparison to pre-NAC derived xenografts, 1,396 circRNAs were dysregulated among post-NAC PDX models. Further, three circRNAs (hsa_circ_001388, hsa_circ_104652, and hsa_circ_061260) were upregulated in Doxo-R, PTX-R, and post-NAC PDX samples compared to their respective controls. Among these three circRNAs, hsa_circ_001388 (also known as circNSD2) was the only transcript also predicted to be translated into a novel and uncharacterized protein given the presence of a high confidence translation initiation site and IRES sequence. Ongoing studies are aimed at determining the role of circNSD2 protein in breast cancer carcinogenesis, progression, and response to standard of care chemotherapeutics and the mechanistic process by which this protein functions. Additionally, the efficacy of specifically targeting this circRNA as a novel therapeutic approach is being explored. Conclusions: Increasing knowledge of the important functions of circRNAs underlying drug resistance will provide new opportunities for developing efficacious therapeutic strategies and prognostic/predictive biomarkers for TNBC. Citation Format: Xiyin Wang, Michael J. Emch, Xiaojia Tang, Jia Yu, Krishna R. Kalari, Liewei Wang, Matthew P. Goetz, John R. Hawse. The role of circular RNAs in triple negative breast cancer and chemotherapy resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1689.

Abstract Chemotherapy-induced cognitive impairment (CICI, also termed “chemobrain”) is a major neurotoxic side effect exhibited by a wide range of chemotherapeutic agents. These side effects affect approximately 14 million cancer survivors. More importantly, CICI persists well after cessation of therapy, severely interfering with quality of life. Unfortunately, there is no treatment and novel therapies are urgently needed. Utilizing cisplatin, a platinum-based chemotherapy, to model chemobrain mice in vivo, we have established that cisplatin accelerates the brain aging process thus leading to long-term memory impairment in mice similar to what is clinically reported. We further show that cisplatin causes oxidative DNA damage, mitochondrial defects, impaired neurogenesis, synaptic defects, and increased gliosis in the adult hippocampus, a brain region critical for learning and memory. Mechanistically, our RNA-sequencing and qRT-PCR analysis revealed that cisplatin dramatically increases COX-2 (Ptgs2) expression and its major product, prostaglandin E2 (PGE2) in adult mouse brain and human cortical neurons derived from induced pluripotent stem cells (iPSCs). Similar as cisplatin treatment, the levels of COX-2 expression began to increase at 0.1 µM methotrexate treatment, which significantly increased at 1 µM in human cortical neurons, indicating that COX-2 induction is a common pathogenic mechanism mediating cognitive impairment associated with cisplatin and methotrexate in spite of the fact that these compounds have different mechanisms of action for cancer eradication. Most importantly, NS-398, a selective COX-2 inhibitor, effectively prevents cognitive deficits in mice and reduction in cell viability of human neurons associated with these chemotherapies, without promoting tumor growth or interfering with cisplatin’s anti-tumor activity. Taken together, our findings strongly suggest that COX-2 induction is a main cause of CICI, making COX-2 inhibition a therapeutic target for CICI. Given that COX-2 inhibitors are currently being tested in cancer prevention as well as age-related memory loss in clinical trials, inhibiting COX-2 may have far-reaching therapeutic effects on CICI and cancer treatment, which can be applied quickly, safely, and effectively to clinical trials, in the effort to improve cancer survivor quality of life. Citation Format: Mohammad Abdur Rashid, Jason J. Tang, Ki-Hyun Yoo, Ana Corujo-Ramirez, Sang Hoon Kim, Alfredo Oliveros, Peter Cole, John R. Hawse, Mi-Hyeon Jang. Blockade of the cyclooxygenase-2 prevents chemotherapy-induced cognitive impairments [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2694.

Abstract Ovarian cancer is the 7th most common cancer in women and the most fatal of all female reproductive cancers, with 5-year overall survival of 10-30%. Despite initial responses to first line platinum- and paclitaxel-based chemotherapies, >70% of ovarian cancers recur with increasingly resistant disease; and nearly all of these women die of their disease. Recently, the use of targeted therapies such as bevacizumab and PARP inhibitors have been shown to improve progression-free survival in a subset of patients. However, these agents have thus far failed to improve overall survival in patients without specific genetic signatures, highlighting the continued need for alternative therapies. Through an unbiased drug screen, we have identified lestaurtinib as a potent inhibitor of many sensitive and resistant ovarian cancer cell lines and patient derived organoid models. Lestaurtinib is a known tyrosine kinase inhibitor originally developed to block FLT3, a protein that is not expressed in any of the ovarian cancer cell lines tested. To elucidate the mechanisms by which lestaurtinib inhibits ovarian cancer cells, we have examined its impact on the phospho-proteome in parallel with RNAseq. Results of these studied have identified inhibition of the JAK/STAT signaling pathway as a top hit. Assessment of STAT1 and STAT3 has revealed that these transcription factors are constitutively activated in chemotherapy- and PARP inhibitor-resistant cell lines as reflected by high levels of Tyr701/705 and Ser727 phosphorylation, suggesting that induction of this pathway may drive resistance. Surprisingly, profound differences in the ability of various JAK/STAT inhibitors to block these specific phosphorylation events is observed, which correlates with their potency. Further, STAT1 and STAT3 ChIPseq experiments following cytokine-mediated activation of this pathway reveal that these transcription factors bind to genomic regions encoding genes involved in oncogenic and drug resistance pathways. Genetic knockdown of STAT1 and STAT3 via siRNA, or knockout via CRISPR/Cas9, results in significant growth inhibition of sensitive and resistant models of ovarian cancer, confirming their importance in maintaining cell viability. Finally, combining lestuartinib with standard-of-care cisplatin or olaparib (a PARP inhibitor) is shown to be synergistic, indicating that pharmacological inhibition of JAK/STAT signaling has the potential to counteract drug resistance. Ongoing studies are aimed at further understanding the role of JAK/STAT signaling in ovarian cancer, elucidating the mechanistic processes by which STAT1/3 mediate progression of this disease, and identifying the most effective pharmacological strategies to study in possible future clinical trials. Citation Format: Esther Rodman, Michael Emch, Elizabeth Bruinsma, Xiaonan Hou, Scott Kaufmann, Saravut J. Weroha, John Hawse. Investigation of the JAK/STAT signaling pathway in chemotherapy and PARP inhibitor resistant ovarian cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4862.

Abstract Background: In phase I/II clinical trials, the tamoxifen metabolite Z-endoxifen (ENDX) demonstrated substantial oral bioavailability and promising antitumor activity in endocrine-refractory estrogen-receptor positive breast cancer (ER+ BC) and other solid tumors, with ENDX plasma concentrations reaching as high as 5 µM, a concentration that far exceeds the ERα-targeting nanomolar concentrations. We previously identified protein kinase C beta 1 (PKCβ1), an oncogenic signaling kinase which regulates cell proliferation and tumorigenic transformation, as a novel ENDX receptor. ENDX-bound PKCβ1 (KD: 100 nM) and inhibited PKCβ1 kinase activity (IC50: 357 nM) in vitro, at concentrations achieved in phase I/II ENDX studies. Given the observations that ENDX induces antitumor activity in breast cancers resistant to endocrine therapies, including AIs, tamoxifen and fulvestrant, we postulated that ENDX may impact additional signaling pathways. Therefore, in this study we performed unbiased mass spectrometry to analyze the effects of ENDX on the phosphoproteome and total proteome. Methods: In estrogen unstimulated aromatase-expressing ER+/human epidermal growth factor 2 receptor negative (HER2-) MCF7AC1 breast cancer cells, the effects of ENDX on the phosphoproteome and total proteome were analyzed using ENDX concentrations achieved in tamoxifen treated patients (0.01 and 0.1 µM) and concentrations observed in the ENDX phase I/II trials (5 µM). NetWorKIN and RoKAI prediction tools were utilized to identify the upstream kinases of ENDX downregulated phosphoproteins. In estrogen unstimulated MCF7AC1 as well as in the ER+/HER2- T47D breast cancer cells, the ability of ENDX, tamoxifen, fulvestrant and PKC kinase inhibitor enzastaurin to block insulin or PKC agonist phorbol 12-myristate 13-acetate (PMA)-stimulated AKTSer473 phosphorylation was analyzed by immunoblot (IB) assay. Additionally, ENDX effects on AKTSer473 phosphorylation in the MCF7AC1 xenograft model in vivo was analyzed by IB assay. Further, the effects of PKCβ1 silencing in MCF7AC1 cells and the effects of AKT inhibitor MK-2206 treatment on growth and AKTSer473 phosphorylation in the MCF7AC1 as well as long-term estrogen deprived T47D (T47D-LTED) cell lines were analyzed by cell proliferation and IB assays. Results: In MCF7AC1 cells unstimulated with estrogen, ENDX at 5 µM but not at 0.01 and 0.1 µM concentrations inhibited growth, and induced apoptosis, suggesting an ERα-independent effect. Further, ENDX at 5 µM displayed three-fold greater effects in downregulating the phosphoproteome compared to the other concentrations, with minimal impact on the total proteome. Protein kinase C beta (PKCβ) and AKT1 were identified as the prevalent upstream kinases for ENDX downregulated protein phosphorylations. Notably, in estrogen unstimulated MCF7AC1 and T47D cells, ENDX at 5 µM attenuated phosphorylation of AKTSer473 and AKT substrates in vitro in the presence of insulin and in vivo. In MCF7AC1 cells, PMA-induced phosphorylation of PKCβ1 as well as AKTSer473 and AKT substrate phosphorylations were blocked by ENDX at 5 µM, with ENDX inducing PKCβ1 protein degradation both in the presence of insulin and PMA. Further, ENDX effects on growth and AKTSer473 phosphorylation were phenocopied by siRNA-mediated PKCβ1 knockdown as well as treatment with the pan-AKT inhibitor, MK-2206. Notably, the potent PKCβ1 kinase inhibitor, enzastaurin, had no effects either on PKCβ1 protein degradation nor on downstream AKT signaling. Conclusion: Taken together, these findings suggest that ENDX may exert anticancer activity via dual effects on blocking ERα as well as by targeting PKCβ1 for degradation, thus suppressing AKT signaling and induction of apoptosis. These preclinical findings will be studied in a planned neoadjuvant trial comparing ENDX with exemestane and ovarian function suppression (EVANGELINE) that will activate in the Fall of 2022. Citation Format: Swaathi Jayaraman, Xinyan Wu, Krishna R. Kalari, Xiaojia Tang, Mary Kuffel, Elizabeth S. Bruinsma, Santosh Renuse, James N. Ingle, Joel Reid, Matthew Schellenberg, John Hawse, Akhilesh Pandey, Matthew P. Goetz. Endoxifen Downregulates AKT Phosphorylation Through Protein Kinase C Beta 1 in ER+/HER2- Breast Cancer. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-11-04.

Abstract Z-Endoxifen Allosterically Inhibits PKCβI and its Paradoxical Membrane Translocation Sayantani Sarkar Bhattacharya1, Taylor L. Witter1, Anh Q. T. Cong1, Elizabeth Bruinsma2, Swaathi Jayaraman2, Matthew P. Goetz2, John R. Hawse1, and Matthew J. Schellenberg1 1Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN USA 55905 2Department of Oncology, Mayo Clinic, Rochester, MN USA 55905 Background: Z-Endoxifen (ENDX), the active metabolite of tamoxifen (TAM) and a selective estrogen receptor modulator (SERM), exhibited high antitumor activity in endocrine-resistant hormone receptor-positive breast and other gynecologic cancer. ENDX has also been shown to be a protein kinase C (PKC) inhibitor. PKCs participate in diverse cellular functions and their activity is often elevated in breast tumors. Guided by mechanistic insights from our recently determined crystal structure of PKCβI, we sought to determine the effects of ENDX on PKCβI in a breast cancer cell line model. Methods: To determine how ENDX regulates PKC activity, we used a Z’LYTE kinase activity assay. This Fluorescence Resonance Energy Transfer (FRET) based biochemical method can detect differential sensitivity of phosphorylated and non-phosphorylated peptides to proteolytic cleavage. We probed changes in activity for conventional and novel PKCs, as well as the purified catalytic domain of conventional PKCs in vitro. Alongside, as kinase activity of PKC relies on its spatial assembly, therefore we studied its intracellular localization using live cell confocal imaging. MCF7 cells expressing YFP-tagged PKCβI were grown in a glass bottom chamber and treated with ENDX and other modulators for relevant time and doses for this study. Images were taken using Zeiss LSM 780 confocal laser scanning microscope and analyzed in Zeiss-ZEN microscope software and GraphPad Prism 9. Results: Our data from an in vitro kinase assay indicates that ENDX inhibits the kinase activity of conventional (PKCβI) and novel (PKC𝛿) PKC isoforms with a similar IC50, however PKCβI catalytic domain is less sensitive to ENDX. We also identified a multi-domain mechanism of PKC inhibition through an allosteric inhibitory mechanism. Our live cell imaging study demonstrated that ENDX promotes the recruitment of PKCβI to the cell membrane in both a dose and time-dependent manner. Moreover, this translocation can also be mitigated by co-treatment with inhibitors of the PKC-regulator PHLPP phosphatases. Conclusion: Taken together, these results suggest the allosteric effects of ENDX trigger PKCβI recruitment to the cell membrane, yet since ENDX also inhibits kinase activity it suggests that ENDX triggers a non-productive interaction with the enzyme and "breaks" the well-known mechanism of PKC activation upon binding the cell membrane. Furthermore, ENDX is likely to trigger dephosphorylation and ultimately degradation, suggesting that ENDX represents a new mechanistic basis for targeting and downregulating PKC in cancer cells. Hence, the current study provides an integrated pattern of highly specific treatments regimen that can exploit PKCβI as a repurposing clinical target in breast cancer. Citation Format: Sayantani Sarkar Bhattacharya, Taylor L. Witter, Anh T. Cong, Elizabeth S. Bruinsma, Swaathi Jayaraman, Matthew P. Goetz, John Hawse, Matthew Schellenberg. Z-Endoxifen Allosterically Inhibits PKCβI and its Paradoxical Membrane Translocation [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-24-03.

Abstract Background: Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer-related death among women worldwide. Triple-negative breast cancer (TNBC) is an aggressive subtype representing 15-20% of all breast cancers. TNBC often ends with a poor clinical outcome due to high histological grade and recurrence rates with few treatment options. Chemotherapy remains the standard of care for TNBC treatment, but unfortunately, patients frequently develop resistance, and alternative treatment strategies for the chemoresistant disease remain a major unmet need. circRNAs are newly identified non-coding RNA molecules with covalently closed circular structures. Recently, an increasing number of studies have indicated that circRNAs play crucial roles in regulating tumor development and chemoresistance. However, the role of circRNAs in the process of TNBC chemotherapy resistance is not yet fully clear. Materials and methods: To study the molecular functions of circRNAs in TNBC chemoresistance, identify alternative biomarkers for chemotherapy-resistant disease, and elucidate novel therapeutic targets, doxorubicin-resistant (Doxo-R) and paclitaxel-resistant (Taxol-R) cell lines were generated using TNBC models. Results: Doxo-R and Taxol-R cells exhibited a 3- and 12-fold decrease in sensitivity to their respective chemotherapeutic agents. We identified a large spectrum of gene expression changes that were acquired in Doxo-R and Taxol-R cells. The expression of circRNAs was profiled using circRNA microarrays, and top hits were validated using RT-PCR. We identified 429 and 310 circRNAs that were differentially expressed in Doxo-R and Taxol-R resistant cells respectively compared to the parental chemosensitive cell line (|FC| ≥ 1.5; p value < 0.05). Of these, 66 were commonly differentially expressed between the two chemotherapy resistant models. Conclusions: These results revealed that Doxo-R and Taxol-R TNBC cell lines were successfully established and serve as good models for studying the mechanisms of chemotherapy resistance and the regulatory roles of circRNAs in the development of chemoresistance in TNBC. Increasing knowledge of the important functions of circRNAs underlying drug resistance will provide new opportunities for developing efficacious therapeutic strategies and prognostic/predictive biomarkers for TNBC. Citation Format: Xiyin Wang, Michael Emch, John Hawse. The role of circular RNAs in triple-negative breast cancer and chemotherapy resistance [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-22-02.

Chemotherapy-induced cognitive impairment (CICI) has emerged as a significant medical problem without therapeutic options. Using the platinum-based chemotherapy cisplatin to model CICI, we revealed robust elevations in the adenosine A 2A receptor (A 2A R) and its downstream effectors, cAMP and CREB, by cisplatin in the adult mouse hippocampus, a critical brain structure for learning and memory. Notably, A 2A R inhibition by the Food and Drug Administration–approved A 2A R antagonist KW-6002 prevented cisplatin-induced impairments in neural progenitor proliferation and dendrite morphogenesis of adult-born neurons, while improving memory and anxiety-like behavior, without affecting tumor growth or cisplatin’s antitumor activity. Collectively, our study identifies A 2A R signaling as a key pathway that can be therapeutically targeted to prevent cisplatin-induced cognitive impairments.

The transcription factor Krüppel-like factor 10 (Klf10), also known as Tieg1 for TGFβ (Inducible Early Gene-1) is known to control numerous genes in many cell types that are involved in various key biological processes (differentiation, proliferation, apoptosis, inflammation), including cell metabolism and human disease. In skeletal muscle, particularly in the soleus, deletion of the Klf10 gene (Klf10 KO) resulted in ultrastructure fiber disorganization and mitochondrial metabolism deficiencies, characterized by muscular hypertrophy. To determine the metabolic profile related to loss of Klf10 expression, we analyzed blood and soleus tissue using UHPLC-Mass Spectrometry. Metabolomics analyses on both serum and soleus revealed profound differences between wild-type (WT) and KO animals. Klf10 deficient mice exhibited alterations in metabolites associated with energetic metabolism. Additionally, chemical classes of aromatic and amino-acid compounds were disrupted, together with Krebs cycle intermediates, lipids and phospholipids. From variable importance in projection (VIP) analyses, the Warburg effect, citric acid cycle, gluconeogenesis and transfer of acetyl groups into mitochondria appeared to be possible pathways involved in the metabolic alterations observed in Klf10 KO mice. These studies have revealed essential roles for Klf10 in regulating multiple metabolic pathways whose alterations may underlie the observed skeletal muscle defects as well as other diseases.