Targeting Cancer Stem Cells Research Articles

Abstract 891: Therapeutic targeting of ovarian cancer stem cells using estrogen receptor beta agonist

Abstract Background: Ovarian cancer (OCa) is the deadliest gynecologic cancer. Emerging studies suggest that ovarian cancer stem cells (OCSCs) contribute to tumor relapse and chemotherapy resistance. Recent studies demonstrate that OCa cells express estrogen receptor beta (ERβ), which functions as a tumor suppressor. However, the status of ERβ expression in OCSCs and the therapeutic utility of ERβ agonist LY500307 for targeting OCSCs remain unknown. In this study, we tested the hypothesis that OCSCs express ERβ and that treatment with ERβ agonist reduces stemness and promotes apoptosis of OCSCs. Methods: We isolated subpopulations of OCSCs from SKOV3, A2780, and patient-derived ascites cells using ALDEFLUOR kit and examined the expression of ERβ in OCSCs using RT-qPCR. The effect of ERβ agonist LY500307 on OCSCs was examined utilizing cell viability, cell cycle, sphere formation, self-renewal, and apoptosis assays. Mechanistic studies were conducted using RNA-seq, RT-qPCR, and Western blot analysis. The efficacy of LY500307 on the tumor-initiating capacity of OCSCs was determined via in vivo limiting dilution assay studies using orthotopic intrabursal xenograft murine models. Results: RT-qPCR assay showed that ERβ, particularly ERβ isoform 1, is highly expressed in OCSCs compared to non-OCSCs. ERβ agonist LY500307 significantly reduced the viability of OCSCs compared to non-OCSCs. Treatment of OCSCs with LY500307 significantly reduced the sphere formation and self-renewal of OCSCs. Further, LY500307 treatment resulted in G2/M cell cycle arrest and promoted the apoptosis of OCSCs. Mechanistic studies using RNA-seq analysis demonstrated that ERβ agonist treatment resulted in the modulation of pathways related to cell cycle and apoptosis. Western blots and RT-qPCR assays confirmed the upregulation of genes involved in apoptosis and cell cycle arrest, such as FDXR and CDKN1A. Importantly, treatment of LY500307 significantly attenuated the tumor-initiating capacity of OCSCs in orthotopically implanted OCa murine models. Conclusions: Our results demonstrate that ERβ agonist LY500307 is highly efficacious in reducing the stemness and promoting apoptosis of OCSCs and may serve as a novel therapeutic agent in treating OCa Citation Format: Yi He, Salvador Alejo, Prabhakar P. Venkata, Jessica D. Johnson, Ilanna Loeffel, Julie Ann Martel, Uday P. Pratap, Suryavathi Viswanadhapalli, Rajeshwar R. Tekmal, Ratna K. Vadlamudi, Edward Kost, Gangadhara R. Sareddy. Therapeutic targeting of ovarian cancer stem cells using estrogen receptor beta agonist [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 891.

Abstract 204: Notch2NL is a novel regulator of radiation sensitivity in non-small cell lung cancer and a positive regulator of MYC activity

Abstract Background: A gain-of-function genetic screen identified NOTCH2 N-terminal like (NOTCH2NL) as a candidate novel gene involved in radiation resistance in non-small cell lung cancer (NSCLC). NOTCH2NL is located on chromosome position 1q21.1 which was incorrectly aligned in previous builds of the reference human genome sequence. NOTCH2NL was derived from a segmental duplication event in NOTCH2 during the evolutionary divergence between humans and non-human primates, forming three Notch2NL proteins: Notch2NL-A, Notch2NL-B and Notch2NL-C. Consequently, the only species whose genomes contain NOTCH2NL are modern and ancient humans. Notch2NL-B is a secreted protein and has been shown to promote Notch signalling in cortical stem cell progenitors via inhibition of inhibitory cis-DLL1/NOTCH signalling. Methods: Stable overexpression of NOTCH2NLB and secreted Notch2NL-B protein were validated by RT-qPCR and Western Blotting. The effects of NOTCH2NLB overexpression; transfer of Notch2NL-B protein from conditioned media onto wild-type cell lines; and siRNA knockdown of NOTCH1-4 transmembrane receptors on Notch signalling were quantified by a Notch luciferase reporter assay, RT-qPCR of classical NOTCH target genes and cancer stem cell marker (CSC) and RNA-Seq. Clonogenic cell survival assays determined the impact of NOTCH2NLB overexpression on radiation response. Cell proliferation was measured using the IncuCyte Zoom system. shRNA stable cell lines to knockdown NOTCH2NL were generated to mitigate the NOTCH2NLB overexpression phenotype we observed. RNA-Seq data from the first 100 patients from the TRACERx lung cancer study was used to quantify hallmark gene expression signatures and NOTCH2NLB expression. Results: NOTCH2NLB overexpression upregulates CSL-dependent Notch reporter luciferase activity; confers a radiation-resistant phenotype and impacts proliferation rate in NSCLC cell lines. Furthermore, we demonstrate that NOTCH2NLB overexpression and secreted Notch2NL-B protein transfer increase expression of classical NOTCH target genes (c-MYC, HES1 and HEY1) and CSC marker, ALDH1A1. Analysis of RNA-Seq data from the Lung TRACERx cohort study shows that NOTCH2NL is commonly expressed in NSCLC. NOTCH2NL expression positively correlates with notch hallmark gene expression signature in squamous (R=0.59, p=5.6e-9) and non-squamous carcinoma (R=0.51, p=4.7e-10). Interestingly, NOTCH2NL expression also positively correlated with the myc hallmark gene expression signature in squamous cell carcinoma (R=0.45, p=2.4e-5). Conclusions: Notch2NL is a novel determinant of radiation therapy response and impacts canonical Notch signalling in lung cancer. It is commonly expressed in NSCLC and can act in a paracrine manner as a secreted protein. Notch2NL, through canonical notch signalling, can regulate MYC expression and increase activity in the MYC pathway. Citation Format: Simranpreet Kaur Summan, Barbara Chow, Rhona Millar, Su Kit Chew, Philip East, Robert Hynds, Carlos Martinez Ruiz, Eva Gronroos, Mariam Jamal-Hanjani, Kevin Litchfield, Nicholas McGranahan, Nnennaya Kanu, Charles Swanton, Crispin Thomas Hiley. Notch2NL is a novel regulator of radiation sensitivity in non-small cell lung cancer and a positive regulator of MYC activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 204.

Abstract 894: CXCR1: A novel therapeutic avenue for CSC-like phenotypes in pancreatic ductal adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related deaths in the United States. Often diagnosed late in disease progression, PDAC is notorious for chemotherapy resistance as well as having metastases. A cell population of interest aiding in this progression is the cancer stem cell (CSC). These cells are known for having high resistance to chemotherapy, along with propagating and re-building the tumor after most non-CSCs have been therapeutically targeted. Previous studies have determined CXCR4, ALDH1, CD24, CD44, and CD133 are markers of PDAC CSCs. In the present study, we investigated CXCR1 as a marker and therapeutic target for PDAC CSCs. CXCR1 is a G-coupled transmembrane protein receptor with downstream effects known to aid in anti-apoptosis, proliferation, and angiogenesis via binding CXCL8 and CXCL6. Already known to be a CSC marker and target in triple-negative breast cancer, initial studies by Chen et al. of CXCR1 in PDAC demonstrate CXCL8 induces increased tumorsphere formation in vitro, leading us to investigate CXCR1 in PDAC CSCs. Considering these findings, we hypothesized that PDAC cells with high CXCR1 activity exhibit increased CSC-like characteristics, and targeting CXCR1 will reduce those characteristics. To investigate the role of CXCR1 in PDAC CSC-like phenotype, we used two PDAC cell lines, CD18/HPAF and T3M4, and developed gemcitabine resistant (GemR) counterparts. These GemR cell lines were shown to have over 10-fold higher resistance than their respective parent cell lines. We treated with the CXCR1/2 antagonist navarixin at concentrations known to inhibit CXCR1. Using the parent cell lines’ relative IC50 concentrations for each drug, we treated cells for 72 hours. We used qRT-PCR and ELISAs for analysis of several known CSC markers and CXCR1 axis expression. From our results, we see the beginning trends of GemR cells having increased expression of CSC markers as well as gemcitabine-treated parent and resistant cells having increased expression. Using flow cytometry, we evaluated the CXCR1+ cell populations post-control and gemcitabine treatment. The population of CXCR1+ cells was higher in the gemcitabine-treated groups. Together, our observations suggest an association between CXCR1 and the CSC-like phenotype in PDAC. Citation Format: Caitlin Molczyk, Elizabeth Thomas, Lubaba Zaman, Paran Goel, Rakesh K. Singh. CXCR1: A novel therapeutic avenue for CSC-like phenotypes in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 894.

Abstract 2: Flavokawain A targets cancer stem cells for inhibiting the growth of prostate cancer

Abstract Prostate cancer stem cells (PCSC) are small tumor subpopulations capable of self-renewal and driving prostate cancer heterogeneity, which is critical for cancer initiation, recurrence, and development of therapeutic resistance. Thus, there’s an urgent need to explore and develop new CSC targeting agents. Flavokawain A (FKA), a novel chalcone from kava plant, can selectively inhibit the growth of pRb deficient cell lines and result in a proteasome-dependent and ubiquitination-mediated Skp2 (S-phase kinase-associated protein 2) degradation, while the potential of FKA to target PCSC is unknown. Therefore, we evaluated the effects of FKA on PCSC self-renewal both in vitro and in vivo. FKA treatment decreased both size and numbers of the tumor spheroids growing from CD44+/CD133+ tumor stem cells, which were sorted out from the prostate tumor cell line DU145 and 22RV1. Expression of the stem cell markers Nanog, Oct4, and Sox2 were all downregulated in the cancer spheroids treated with FKA. Growth of the 22RV1CD44+/CD133+ xenograft tumors was significantly inhibited in FKA diet-fed mice compared to the vehicle control diet-fed mice. Immunohistochemistry analysis revealed less positive Ki67, Nanog, and Oct4 cells in tumor tissues from the FKA dietary group than those from the control dietary group. These results demonstrated that FKA can inhibit prostate cancer stemness and suggested a potential role of FKA for preventing prostate cancer recurrence by targeting PCSC. Citation Format: Liankun Song, Merci Mino, Jana Yamak, Vyvyan Nguyen, Derron Lopez, Victor Pham, Ali Fazelpour, Vinh Le, Dongjun Fu, Matthew Tippin, Xiaolin Zi. Flavokawain A targets cancer stem cells for inhibiting the growth of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2.

Abstract 1523: Beta-2 adrenergic receptor and mu opioid receptor interact to increase the aggressiveness in triple negative breast cancer cells through activation of GSK3 signaling

Abstract Breast cancer is the world’s leading cause of cancer mortality in women worldwide. It has been shown that body stress hormones, such as norepinephrine, and opioid peptides interact to control the growth and progression of this cancer. Opioid and beta-adrenergic receptors are recently shown to cross talk via formation of receptor heterodimers to control cellular functions in various cell systems. However, the underlying cell signaling mechanism remains unclear. To determine the effect of the interaction of the two systems in breast cancer, we employed triple-negative breast cancer (TNBC) cell lines MDA-MB-231 and MDA-MB-468, CRISPR, chemical inhibition or activation and, PCR Array technology to study aggressive tumor phenotype and signaling cascades. We found that knock down of the beta-adrenergic (B2AR) or mu-opioidergic receptor (MOR) system via the CRISPR technique or pharmacological agents induces a less aggressive phenotype in triple negative breast cancer cells both in vitro and in vivo, with the effect being potentiated when both receptor systems were inhibited together. The mRNA expression study using a PCR Array targeting Cancer Stem Cell genes shows that B2AR or MOR activated the glycogen synthase kinase 3 (GSK3) signaling cascade. The GSK3 inactivation in MDA-MB-231 and MDA-MB-468 cells induced similar phenotypic changes as was done by the inhibition of B2AR and/or MOR, while a GSK3 activation by wortmannin reversed the effects of B2AR and/or MOR knockdown on these cells. GSK3 inactivation also prevents B2AR agonist norepinephrine or MOR agonist DAMGO from affecting MDA-MB-231 and MDA-MB-468 cell proliferation. These data identify a role of B2AR and MOR interaction in the control of breast cancer cell growth and establish a possible role of the GSK3 signaling system in mediation of these two receptors’ cross talk. (Supported by NIH grant R01 CA20863201). Citation Format: Bénédicte Rousseau, Sengottuvelan Murugan, Ajay Palagani, Dipak K. Sarkar. Beta-2 adrenergic receptor and mu opioid receptor interact to increase the aggressiveness in triple negative breast cancer cells through activation of GSK3 signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1523.

Abstract 6073: First-in-class Doublecortin-like kinase 1 (DCLK1) inhibitor for targeting cancer stem cell in hepatocellular carcinoma

Abstract Cancer stem cells (CSCs) have been considered promising therapeutic targets for cancer therapy. These cells have self-renewal capacity and differentiation potential and contribute to multiple tumor malignancies, such as recurrence, metastasis, heterogeneity, multidrug resistance, and radiation resistance. Doublecortin-like kinase 1 (DCLK1) was recently identified as CSC marker is upregulated in several solid tumors, which distinguishes between cancer and normal stem cell. However, the role of DCLK1 in hepatocellular carcinoma (HCC) is unclear. According to the open database like TCGA, overexpression of DCLK1 is reported to be associated with poor prognosis in HCC patients. It was also observed that DCLK1 expression was significantly increased in the advanced stage of HCC. In addition, as a result of measuring the serum DCLK1 levels obtained from patients with liver cirrhosis or HCC treated at Seoul National University Hospital, it was confirmed that the expression of DCLK1 was significantly increased in patients with HCC compared to those with liver cirrhosis. It was also confirmed that DCLK1 was expressed in human HCC cell lines and that the expression levels of DCLK1 mRNA and protein were further increased in CSC rich human HCC cell lines. Moreover, cell death was increased at the cellular level when DCLK1 was blocked via inhibiting expression of CSC markers such as CD133 and EpCAM. After evaluating the effect of DCLK1 inhibition in CSC rich human HCC cells lines, it was found that spheroid formation decreased by suppressing CSCs markers including LGR5 and CD133. In addition, it was confirmed that cell migration decreased when DCLK1 was blocked. Even in the murine HCC model, it was found that the antitumor effect was showed when administered with DCLK1 inhibitor, DCLK1-IN-1, in xenograft model with CSC rich HCC cell lines. Our results support that DCLK1 can be used as a biomarker for the detection of HCC and may be a candidate for developing targeted therapeutics to eradicate HCC. Citation Format: Daseul Yoon, Seung Hee Jung, Ju Young Jang, Ji-Young Ahn, Seung Jin Jo, Donghyun Ko, Dong-kyu Kim, Su Jong Yu. First-in-class Doublecortin-like kinase 1 (DCLK1) inhibitor for targeting cancer stem cell in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6073.

Abstract 305: Novel nanoformulation of piperlongumine for pancreatic cancer therapy

Abstract Background: Pancreatic cancer (PanCa) is expected to be the second leading cause of cancer-related death by 2030. The treatment of PanCa is highly challenging due to the extremely poor response to existing therapeutic options. Highly desmoplastic tumor microenvironment in pancreatic tumor causes suboptimal delivery of therapeutic agents in tumors that eventually resulted to chemo-resistance. Piperlongumine (PL) is a natural alkaloid isolated from the long pepper, Piper longum L., and has shown substantial cancer-preventive and therapeutic efficacy against variety of cancers. However, delivering its effective concentration in pancreatic tumors has been challenging. In this study, we have synthesized and characterized a novel nano-formulation of PL composed of a PLGA core (PLGA-PL), stabilized with polyvinyl alcohol (PVA) and coated with poly-L-lysine (PLL), and evaluated its therapeutic effects against PanCa. Methods: The various physicochemical approaches (FT-IR, DSC, TEM, TGA, and HPLC) was used to characterize the PLGA-PL formulation for particle size, chemical composition, and drug loading efficiency. Cellular uptake of PLGA-PL was achieved in incubation with PLGA-PL in PanCa cells. Further, the therapeutic efficacy of PLGA-PL was determined by using various in vitro assays (MTS, wound healing, boyden chamber, cell cycle and apoptosis assays) using PanCa cells. The effects of PLGA-PL on various key oncogenic signaling pathways were evaluated by qRT-PCR, Western blot, confocal microscopy, immunohistochemistry (IHC) analyses. Results: Our novel PLGA-PL formulation has an average size of 110 nm in dynamic light scattering and a zeta potential range of -6.52 to -7.68 mV with excellent PL loading efficiency. Cellular uptake and internalization studies show that PLGA-PL escapes lysosomal degradation, allowing for effective endosomal release into the cytosol. PLGA-PL showed superior anti-cancer activity in various PanCa cells (BxPC-3, HPAF-II, AsPC-1, Panc-1, and MIA PaCa-2) compared to free PL. Moreover, PLGA-PL showed a remarkable inhibition of the migration and invasion potential of PanCa cells. Furthermore, PLGA-PL more effectively inhibited the components of the Shh pathway and Gli targets as determined by qPCR and Western blot analysis. Additionally, PLGA-PL treatment targets cancer stem cells by regulating pluripotency, maintaining stemness factors (Oct-4, Sox2, Nanog and c-Myc), and limiting tumor sphere formation. Conclusions: Taken together, our results demonstrate that PLGA-PL nanoformulation exhibits superior anti-cancer potential than free PL against and could be used as a novel therapeutic modality for the management of PanCa. Citation Format: Vivek Kumar Kashyap, Godwin P. Darkwah, Swati Dhasmana, Neeraj Chauhan, Anupam Dhasmana, Sudhir Kotnala, Partha Laskar, Mohammed Sikander, Bilal B. Hafeez, Murali M. Yallapu, Meena Jaggi, Subhash C. Chauhan. Novel nanoformulation of piperlongumine for pancreatic cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 305.

Abstract 3712: The C-terminal HSP90 inhibitor, a novel deguelin derivative, exerts anti-metastatic effects in triple-negative breast cancer by targeting cancer stem-like properties

Abstract Purpose: Triple-negative breast cancer (TNBC) still relies on non-selective cytotoxic anticancer agents due to the absence of established molecular targets for the phenotype. The heat shock protein 90 (HSP90) is a promising therapeutic target because it affects the overall progression of cancer, including cell proliferation, angiogenesis and metastasis. A variety of N-terminal HSP90 inhibitors have been tried several times in clinical trials, but none have been approved for clinical use to date due to issues including heat shock response (HSR) induction, undesirable effects, and clinical toxicity. In this study, we sought to investigate whether a novel C-terminal HSP90 inhibitor SL-145 could resolve metastasis in TNBC through inhibition of cancer stem-like properties. Experimental Design: The effects of SL-145 on TNBC cell lines in vitro were evaluated in terms of cell proliferation, apoptosis, caspase-3 activity, breast cancer stem cell (BCSC)-like properties and heat shock response. An orthotopic allograft model with 4T1 mammospheres was used to examine the effect of SL-145 on tumor growth and metastasis in vivo. Results: SL-145 induces apoptosis without triggering the HSR and simultaneously inhibits several oncogenic signaling pathways including AKT, MEK/ERK and JAK2/STAT3. SL-145 effectively targets BCSC-like properties with significant reductions in CD44, CD49f and ALDH1 expression as well as impairment of mammosphere-forming ability. To confirm the physiological relevance of our in vitro observations, we investigated the effects of SL-145 on tumor growth, angiogenesis and metastasis in mammosphere-derived allograft tumors with self-renewal capacity. SL-145 administration reduced tumor burden and angiogenesis, which were enriched in BCSCs, and it resulted in significant reductions in lung and liver metastases. In addition, no toxic effects of inhibitors on markers of liver or renal function were observed. Conclusion: Our findings suggest that SL-145 may represent an effective therapeutic approach for targeting cancer stem cells and simultaneous inhibition of the HSP90 client oncoprotein to treat TNBC with a heterogeneous and aggressive nature. Citation Format: Minsu Park, Tae-Min Cho, Soeun Park, Jung Min Park, Juyeon Seo, Dongmi Ko, Seongjae Kim, So Ra Seuk, Yong Gu Kang, Kee Dal Nam, Yoon-Jae Kim, Ji Young Kim, Jae Hong Seo. The C-terminal HSP90 inhibitor, a novel deguelin derivative, exerts anti-metastatic effects in triple-negative breast cancer by targeting cancer stem-like properties [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3712.

Abstract 3164: Detection and CAR T-cell directed targeting of inflammation-responsive Wnt pathway receptors on multiple myeloma cancer stem-like cells

Abstract Multiple myeloma (MM) is the second most common hematological malignancy characterized by a malignant expansion of abnormal antibody-producing cells. Despite available treatments, relapsed disease is a common occurrence with patients receiving survival predictions of less than one year. Relapsed MM is often refractory to multiple lines of therapy and occurs due to the uncontrolled regeneration of a population of malignant cells displaying progenitor-cell-like phenotypes. Selectively targeting this cancer stem cell (CSC) population provides an effective way to limit incidence of relapsed disease, improving the prognosis for high-risk patients. In MM, the defining characteristics of CSCs remain poorly understood, though signaling pathways promoting ‘stemness’ that are often deregulated in CSCs, such as interleukin-6 (IL-6) signaling, as well as canonical and non-canonical Wnt signaling are also aberrantly activated in MM. In this context, the central objective of this project was to explore the functionality of two proteins which have been shown to be downstream targets of IL-6/JAK2/STAT3 signaling and potentiate Wnt signaling, the embryonic G-protein coupled receptor LGR4 and the fetal-oncogene tyrosine kinase like orphan receptor-1 (ROR1), as CSC biomarker candidates, and explore the feasibility of CSC targeting therapeutics for MM. Receptor expression was assessed by quantitative PCR and flow cytometry in primary plasma cell dyscrasia patient samples across the spectrum of disease, as well as in human myeloma cell lines (HMCLs). Whole transcriptome sequencing analyses were carried out in HMCLs induced to overexpress LGR4, which enriched genes associated with ion transport and embryonic development. Cell adhesion and extracellular matrix genes were downregulated, along with genes associated with metabolic and mitochondrial pathways. Results of ROR1 gene expression and flow cytometry studies suggest that a subset of MM patient samples harbor a low-frequency ROR1-positive cell population, and expression is enriched in an in vitro model of acquired drug resistance. Overexpression of interferon regulatory factor-4 (IRF4) - a myeloma cell-enriched transcription factor that we recently showed promotes myeloma regeneration - also contributed to increased human ROR1 protein levels. HMCLs with high endogenous ROR1 expression were sensitive to in vitro killing by anti-ROR1 CAR T-cell treatment, which employs an scFv generated from the fully humanized ROR1-specific monoclonal antibody cirmtuzumab, at effector:target cell ratios (ET) as low as 0.33:1. Together, these results suggest a central role for Wnt signaling in MM stem cell phenotypes and activation of embryonic transcriptional pathways, while also paving the way towards development of clinical therapies that target a CSC population in MM. Citation Format: Lara C. Avsharian, Christopher S. Oh, Ashni A. Vora, Jayde Fernandez, Caitlin Shin, Navyaa Sinha, Charles Prussak, Leslie Crews. Detection and CAR T-cell directed targeting of inflammation-responsive Wnt pathway receptors on multiple myeloma cancer stem-like cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3164.

Abstract 902: Identification, characterization, and targeting of desmoplastic small round cell tumor cancer stem cell-like cells

Abstract Desmoplastic Small Round Cell Tumor (DSRCT) is a rare and aggressive form of pediatric cancer caused by a translocation between chromosomes 11 and 22, creating the novel EWSR1-WT1 fusion gene. Current therapy including surgery and the P6 chemotherapy regimen is insufficient, leading to a 5-year survival rate of only 15-25%. One potential explanation for this poor prognosis is the existence of a cancer stem cell (CSC) population with the ability to resist chemotherapy and cause both tumor recurrence and metastasis. While a CSC population has been identified in the closely related Ewing Sarcoma, most commonly caused by the EWSR1-FLI1 fusion gene, no CSC population has yet been identified in DSRCT. In this study, novel culture conditions were developed that enabled the formation of tumorspheres in vitro in the two commonly available DSRCT cell lines: JN-DSRCT-1 and BER-DSRCT. These novel culture conditions led to upregulation of stemness genes at the RNA and protein level including NANOG and SOX2, two genes that are associated with poor survival outcomes in TCGA sarcomas data. CCK-8 assay demonstrated an increased chemoresistance for tumorspheres versus normal adherent culture especially for doxorubicin, which was confirmed by reduction in PARP cleavage. This chemoresistance may be partially explained by a more quiescent CSC state as shown by reduced cell proliferation and a lower percentage of cells in the S and G2/M phases. However, cells grown in tumorspheres still robustly formed tumors in vivo, thus demonstrating the two hallmark CSC traits of chemoresistance and tumor formation. RNA-seq was performed to elucidate key differences between the adherent and sphere culture conditions and identify potential targets for the therapeutically important CSC-like population. Overrepresentation analysis and gene set enrichment analysis both showed upregulation of pathways related to chromatin assembly and disassembly, suggesting epigenetic changes as DSRCT cells move to a more stem-like state. RNA-seq further revealed kinases upregulated in tumorspheres including B-lymphocyte kinase (BLK) which previous studies have demonstrated is oncogenic, regulated by EWSR1-WT1, and not necessary for normal survival. BLK knockdown reduced CSC-like properties including abrogation of tumorsphere formation and reduction in the levels of SOX2 and NANOG. Together, this work for the first time identifies a CSC-like population in DSRCT and BLK as a potential DSRCT CSC target. Citation Format: Justin W. Magrath, Alifiani B. Hartono, Sean B. Lee. Identification, characterization, and targeting of desmoplastic small round cell tumor cancer stem cell-like cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 902.

Abstract 2880: CD133-targeting silicate prodrug nanoparticles for effective cancer stem cell targeting

Abstract Cancer stem cells (CSCs) are considered to be key contributors to drug resistance and tumor recurrence in many solid tumors. Therapeutic approaches that specifically target these cells are needed to improve treatment outcomes in these tumor types. We are investigating CD133, a widely used surface marker to identify CSCs in colon, brain, and breast tumors. Here, we report the use of polymeric nanoparticles targeting CD133 by conjugating an anti-CD133 scFv-Fc to poly(L-lactide)-PEG-maleimide nanoparticles (anti-CD133 NPs) for effective CSC targeting. The Fc tagged anti-CD133 scFv was prepared and purified using an Expi293 expression system. Nanoparticles were prepared using flash nanoprecipitation and loaded with a hydrophobic, hydrolytically labile, silicate prodrug of paclitaxel. Flash nanoprecipitation allowed for generation of particles with a size of 232 ± 17 nm (increased to 289 ± 23 nm upon scFv conjugation), a zeta potential of -11.5 mV and a drug loading of 57 ± 8 wt% measured by HPLC. The anti-CD133 scFv-Fc was thiolated using 2-iminothiolane (2-IT) and conjugated to nanoparticles using thiol-maleimide chemistry. Thiolation of the antibody was optimized using different molar excesses of 2-IT. A binding assay using Caco-2 cells (which overexpress CD133) confirmed that thiolation of the antibody did not affect its binding, even at the highest molar excess of 2-IT used. With 200x molar excess of 2-IT, 2.9 thiols per antibody were added. Antibody conjugation was confirmed using gel electrophoresis; bands corresponding to the heavy and light chains of antibody were observed for anti-CD133 NPs after reduction but were not seen for non-reduced anti-CD133 NPs or for unconjugated particles. Cytotoxicity studies in MDA-MB-231-LM2 cells revealed maximum kill in drug loaded anti-CD133 NPs, which was significantly higher than for either non-targeted, drug-loaded nanoparticles or blank nanoparticles (p<0.05). Overall, these studies indicate the potential for using anti-CD133 scFv-Fc in conjunction with FNP-produced silicate prodrug nanoparticles of paclitaxel for efficient targeting of CSCs. Citation Format: Shubhmita Bhatnagar, Mengyuan Jin, Thomas Hoye, Jayanth Panyam. CD133-targeting silicate prodrug nanoparticles for effective cancer stem cell targeting [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2880.

Targeting colon cancer stem cells using novel doublecortin like kinase 1 antibody functionalized folic acid conjugated hesperetin encapsulated chitosan nanoparticles

The cancer stem cell (CSC) hypothesis is an evolving oncogenesis concept. CSCs have a distinct ability to self-renew themselves and also give rise to a phenotypically diverse population of cells. Targeting CSCs represents a promising strategy for cancer treatment. Plant-derived compounds are potent in restricting the expansion of CSCs. DCLK1 has been already reported as a colon CSC specific marker. Nanoparticles can effectively inhibit multiple types of CSCs by targeting specific markers. We have synthesized DCLK1 functionalized folic acid conjugated hesperetin encapsulated chitosan nanoparticles (CFH-DCLK1), specifically to target CSCs. In this regard, we have performed proliferation assay, colony formation assay, cell migration assay, apoptosis assay, flow cytometry analysis, real-time RT- PCR and western blot analyses to determine the effect of CFH-DCLK1 and CFH nanoparticles in HCT116-colon cancer cells. In our study, we have determined the median inhibitory concentration (IC50) of CFH (47.8 µM) and CFH-DCLK1 (4.8 µM) nanoparticles in colon cancer cells. CFH-DCLK1 nanoparticles induced apoptosis and inhibited the migration and invasion of colon cancer cells. Real time PCR and western blot results have demonstrated that the treatment with CFH-DCLK1 nanoparticles significantly reduced the expression of CSC markers such as DCLK1, STAT1 and NOTCH1 compared to the CFH alone in HCT116 colon cancer cells. Finally, in the 3D spheroid model, CFH-DCLK1 nanoparticles significantly inhibited the colonosphere growth. Overall, our results highlight the effectiveness of CFH-DCLK1 nanoparticles in targeting the colon cancer cells and CSCs. This study would lead to the development of therapies targeting both cancer cells and CSCs simultaneously using nanoformulated drugs, which could bring changes in the current cancer treatment strategies.

Single-Cell Sequencing Reveals that DBI is the Key Gene and Potential Therapeutic Target in Quiescent Bladder Cancer Stem Cells.

Background: Drug resistance and recurrence often develop during the treatment of muscle-invasive bladder cancer (MIBC). The existence of cancer stem cells (CSCs) in MIBC makes the formulation of effective treatment strategies extremely challenging. We aimed to use single-cell RNA sequencing approaches to identify CSCs and evaluate their molecular characteristics and to discover possible therapeutic measures. Methods: GEO data sets GSE130001 and GSE146137 were used to construct an expression matrix. After cells were identified by type, malignant epithelial cells inferred by InferCNV were extracted for stemness evaluation. The subset of cells with the highest stemness was subjected to weighted gene coexpression network analysis (WGCNA) and pseudotime analysis to identify key genes. In addition, we predicted drug sensitivity relationships for key genes in CTD and predicted the correlation between drugs and survival through siGDC. Results: We found that there were some CSCs in MIBC samples. The CSC population was heterogeneous during tumor development and was divided into quiescent and proliferating CSCs. We identified DBI as the key gene in quiescent CSCs. Analysis of a TCGA data set showed that higher DBI expression indicated higher histological grade. In addition, we predicted that acetaminophen can reduce DBI expression, thereby reducing the stemness of CSCs. Thus, we identified a potential new use of acetaminophen. Conclusion: We systematically explored CSCs in tumors and determined that DBI may be a key gene and potential therapeutic target in quiescent CSCs. In addition, we confirmed that acetaminophen may be a candidate drug targeting CSCs, improving our understanding of CSC-targeting therapeutic strategies.

A Functional Screening Identifies a New Organic Selenium Compound Targeting Cancer Stem Cells: Role of c-Myc Transcription Activity Inhibition in Liver Cancer.

Cancer stem cells (CSCs) are reported to play essential roles in chemoresistance and metastasis. Pathways regulating CSC self‐renewal and proliferation, such as Hedgehog, Notch, Wnt/β‐catenin, TGF‐β, and Myc, may be potential therapeutic targets. Here, a functional screening from the focused library with 365 compounds is performed by a step‐by‐step strategy. Among these candidate molecules, phenyl‐2‐pyrimidinyl ketone 4‐allyl‐3‐amino selenourea (CU27) is chosen for further identification because it proves to be the most effective compound over others on CSC inhibition. Through ingenuity pathway analysis, it is shown CU27 may inhibit CSC through a well‐known stemness‐related transcription factor c‐Myc. Gene set enrichment analysis, dual‐luciferase reporter assays, expression levels of typical c‐Myc targets, molecular docking, surface plasmon resonance, immunoprecipitation, and chromatin immunoprecipitation are conducted. These results together suggest CU27 binds c‐Myc bHLH/LZ domains, inhibits c‐Myc‐Max complex formation, and prevents its occupancy on target gene promoters. In mouse models, CU27 significantly sensitizes sorafenib‐resistant tumor to sorafenib, reduces the primary tumor size, and inhibits CSC generation, showing a dramatic anti‐metastasis potential. Taken together, CU27 exerts inhibitory effects on CSC and CSC‐associated traits in hepatocellular carcinoma (HCC) via c‐Myc transcription activity inhibition. CU27 may be a promising therapeutic to treat sorafenib‐resistant HCC.

Rationally Screened and Designed ABCG2-Binding Aptamers for Targeting Cancer Stem Cells and Reversing Multidrug Resistance.

The ATP-binding cassette, subfamily G, isoform 2 protein (ABCG2), as an important member of ABC transporters, plays a key role in multidrug resistance (MDR) in cancer and has been widely considered as a marker of cancer stem cells (CSC). Reagents capable of simultaneously targeting ABCG2 and reversing MDR have great clinical application values, but their development is highly challenging. Herein, ABCG2 glycosylated extracellular region-binding aptamers were efficiently screened by a cladded molecularly imprinted polymer (cMIP)-based in vitro screening method and further rationally engineered into cyclic bivalent aptamers. Experiments showed that both the monovalent and cyclic bivalent aptamers could specifically bind ABCG2 and thereby specially target CSC of human colorectal carcinomas (CoCSC), while the latter could effectively reverse MDR in drug-resistant liver cancer cells (HepG2/ADR). Different from currently predominant small molecule inhibitors, the reversal of MDR relied on a different mechanism; the cyclic bivalent aptamers bound the two monomers of ABCG2 dimers simultaneously and thereby blocked the ABCG2-mediated drug-pumping channel, resulting in increased intracellular accumulation of substrate drugs. This study opened a new access to the development of affinity reagents for targeting CSC and reversing MDR, holding great prospects in cancer diagnosis and treatment.

Role of Intracellular Iron in Switching Apoptosis to Ferroptosis to Target Therapy-Resistant Cancer Stem Cells.

Iron is a crucial element required for the proper functioning of the body. For instance, hemoglobin is the vital component in the blood that delivers oxygen to various parts of the body. The heme protein present in hemoglobin comprises iron in the form of a ferrous state which regulates oxygen delivery. Excess iron in the body is stored as ferritin and would be utilized under iron-deficient conditions. Surprisingly, cancer cells as well as cancer stem cells have elevated ferritin levels suggesting that iron plays a vital role in protecting these cells. However, apart from the cytoprotective role iron also has the potential to induce cell death via ferroptosis which is a non-apoptotic cell death dependent on iron reserves. Apoptosis a caspase-dependent cell death mechanism is effective on cancer cells however little is known about its impact on cancer stem cell death. This paper focuses on the molecular characteristics of apoptosis and ferroptosis and the importance of switching to ferroptosis to target cancer stem cells death thereby preventing cancer relapse. To the best of our knowledge, this is the first review to demonstrate the importance of intracellular iron in regulating the switching of tumor cells and therapy resistant CSCs from apoptosis to ferroptosis.

Antagonizing RARγ Drives Necroptosis of Cancer Stem Cells

There is a need for agents that eliminate cancer stem cells, which sustain cancer and are also largely responsible for disease relapse and metastasis. Conventional chemotherapeutics and radiotherapy are often highly effective against the bulk of cancer cells, which are proliferating, but spare cancer stem cells. Therapeutics that target cancer stem cells may also provide a bona fide cure for cancer. There are two rationales for targeting the retinoic acid receptor (RAR)γ. First, RARγ is expressed selectively within primitive cells. Second, RARγ is a putative oncogene for a number of human cancers, including cases of acute myeloid leukemia, cholangiocarcinoma, and colorectal, renal and hepatocellular carcinomas. Prostate cancer cells depend on active RARγ for their survival. Antagonizing all RARs caused necroptosis of prostate and breast cancer stem cell-like cells, and the cancer stem cells that gave rise to neurospheres from pediatric patients’ primitive neuroectodermal tumors and an astrocytoma. As tested for prostate cancer, antagonizing RARγ was sufficient to drive necroptosis. Achieving cancer-selectively is a longstanding paradigm for developing new treatments. The normal prostate epithelium was less sensitive to the RARγ antagonist and pan-RAR antagonist than prostate cancer cells, and fibroblasts and blood mononuclear cells were insensitive. The RARγ antagonist and pan-RAR antagonist are promising new cancer therapeutics.

Impairment of Glucose Metabolism and Suppression of Stemness in MCF-7/SC Human Breast Cancer Stem Cells by Nootkatone.

Targeting cancer stem cell metabolism has emerged as a promising therapeutic strategy for cancer treatment. Breast cancer stem cells (BCSCs) exert distinct metabolism machinery, which plays a major role in radiation and multidrug resistance. Therefore, exploring the mechanisms involved in energy utilization of BCSCs could improve the effectiveness of therapeutic strategies aimed at their elimination. This study was conducted to clarify the glucose metabolism machinery and the function of nootkatone, a bioactive component of grapefruit, in regulating glucose metabolism and stemness characteristics in human breast carcinoma MCF-7 stem cells (MCF-7SCs). In vivo experiments, transcriptomic analysis, seahorse XF analysis, MTT assay, Western blotting, mammosphere formation, wound healing, invasion assay, flow cytometric analysis, reverse transcription-quantitative polymerase chain reaction, and in silico docking experiments were performed. MCF-7SCs showed a greater tumorigenic capacity and distinct gene profile with enrichment of the genes involved in stemness and glycolysis signaling pathways compared to parental MCF-7 cells, indicating that MCF-7SCs use glycolysis rather than oxidative phosphorylation (OXPHOS) for their energy supply. Nootkatone impaired glucose metabolism through AMPK activation and reduced the stemness characteristics of MCF-7SCs. In silico docking analysis demonstrated that nootkatone efficiently bound to the active site of AMPK. Therefore, this study indicates that regulation of glucose metabolism through AMPK activation could be an attractive target for BCSCs.

Emerging Nanotherapeutic Approaches to Overcome Drug Resistance in Cancers with Update on Clinical Trials.

A key issue with modern cancer treatments is the emergence of resistance to conventional chemotherapy and molecularly targeted medicines. Cancer nanotherapeutics were created in order to overcome the inherent limitations of traditional chemotherapeutics. Over the last few decades, cancer nanotherapeutics provided unparalleled opportunities to understand and overcome drug resistance through clinical assessment of rationally designed nanoparticulate delivery systems. In this context, various design strategies such as passive targeting, active targeting, nano-drug, and multimodal nano-drug combination therapy provided effective cancer treatment. Even though cancer nanotherapy has made great technological progress, tumor biology complexity and heterogeneity and a lack of comprehensive knowledge of nano-bio interactions remain important roadblocks to future clinical translation and commercialization. The current developments and advancements in cancer nanotherapeutics employing a wide variety of nanomaterial-based platforms to overcome cancer treatment resistance are discussed in this article. There is also a review of various nanotherapeutics-based approaches to cancer therapy, including targeting strategies for the tumor microenvironment and its components, advanced delivery systems for specific targeting of cancer stem cells (CSC), as well as exosomes for delivery strategies, and an update on clinical trials. Finally, challenges and the future perspective of the cancer nanotherapeutics to reverse cancer drug resistance are discussed.

HOX and PBX gene dysregulation as a therapeutic target in glioblastoma multiforme

BackgroundGlioblastoma multiforme (GBM) is the most common high-grade malignant brain tumour in adults and arises from the glial cells in the brain. The prognosis of treated GBM remains very poor with 5-year survival rates of 5%, a figure which has not improved over the last few decades. Currently, there is a modest 14-month overall median survival in patients undergoing maximum safe resection plus adjuvant chemoradiotherapy. HOX gene dysregulation is now a widely recognised feature of many malignancies.MethodsIn this study we have focused on HOX gene dysregulation in GBM as a potential therapeutic target in a disease with high unmet need.ResultsWe show significant dysregulation of these developmentally crucial genes and specifically that HOX genes A9, A10, C4 and D9 are strong candidates for biomarkers and treatment targets for GBM and GBM cancer stem cells. We evaluated a next generation therapeutic peptide, HTL-001, capable of targeting HOX gene over-expression in GBM by disrupting the interaction between HOX proteins and their co-factor, PBX. HTL-001 induced both caspase-dependent and –independent apoptosis in GBM cell lines.ConclusionIn vivo biodistribution studies confirmed that the peptide was able to cross the blood brain barrier. Systemic delivery of HTL-001 resulted in improved control of subcutaneous murine and human xenograft tumours and improved survival in a murine orthotopic model.