Nobu Oshima

Induction of Cancer Stem Cell Properties in Colon Cancer Cells by Defined Factors

Cancer stem cells (CSCs) are considered to be responsible for the dismal prognosis of cancer patients. However, little is known about the molecular mechanisms underlying the acquisition and maintenance of CSC properties in cancer cells because of their rarity in clinical samples. We herein induced CSC properties in cancer cells using defined factors. We retrovirally introduced a set of defined factors (OCT3/4, SOX2 and KLF4) into human colon cancer cells, followed by culture with conventional serum-containing medium, not human embryonic stem cell medium. We then evaluated the CSC properties in the cells. The colon cancer cells transduced with the three factors showed significantly enhanced CSC properties in terms of the marker gene expression, sphere formation, chemoresistance and tumorigenicity. We designated the cells with CSC properties induced by the factors, a subset of the transduced cells, as induced CSCs (iCSCs). Moreover, we established a novel technology to isolate and collect the iCSCs based on the differences in the degree of the dye-effluxing activity enhancement. The xenografts derived from our iCSCs were not teratomas. Notably, in contrast to the tumors from the parental cancer cells, the iCSC-based tumors mimicked actual human colon cancer tissues in terms of their immunohistological findings, which showed colonic lineage differentiation. In addition, we confirmed that the phenotypes of our iCSCs were reproducible in serial transplantation experiments. By introducing defined factors, we generated iCSCs with lineage specificity directly from cancer cells, not via an induced pluripotent stem cell state. The novel method enables us to obtain abundant materials of CSCs that not only have enhanced tumorigenicity, but also the ability to differentiate to recapitulate a specific type of cancer tissues. Our method can be of great value to fully understand CSCs and develop new therapies targeting CSCs.

miR-137 Regulates the Tumorigenicity of Colon Cancer Stem Cells Through the Inhibition of DCLK1

miRNAs have important roles in regulating cancer stem cell (CSC) properties and are considered to be potential therapeutic targets. However, few studies have focused on miRNAs which are specifically related to colon CSCs. Here, a PCR-based miRNA profiling analysis of normal colon stem cells (NCSC) and colon CSCs (EpCAM+/CD44+/CD66a−) identified miRNAs which regulate colon CSC properties. Interestingly, miRNA-137 (miR-137) expression was downregulated in the colon CSCs compared with NCSCs, while doublecortin-like kinase 1 (DCLK1) mRNA was highly expressed in the colon CSCs but low in the NCSCs. In fact, DCLK1-positive cancer cells were widely distributed in clinically resected colon cancer specimens, while DCLK1-positve epithelial cells were rarely detected in normal colon tissues including the crypt bottoms. Luciferase assay and immunoblot analysis revealed that miR-137 regulated DCLK1 gene expression. Transduction of exogenous miR-137 suppressed the development of colon cancer organoids in vitro and the tumorigenicity of colon cancer cells in vivo without affecting the growth of normal intestinal organoids. Furthermore, the suppression of miR-137 enhanced the organoid development of normal colon cells. These data demonstrate that miR-137 has the capacity to suppress the tumorigenicity of colon CSCs and that maintained expression of miR-137 in NCSCs contributes to suppressing uncontrolled cell proliferation through the inhibition of DCLK1 expression. Implications: The miR-137/DCLK1 axis as an important regulator in NCSCs and colon CSCs; further understanding of this axis may foster the development of potential gene therapeutic strategies targeting colon CSCs. Mol Cancer Res; 14(4); 354–62. ©2016 AACR.

Surgical Therapy for a Solitary Form of Hepatic Epithelioid Hemangioendothelioma: A Long-Term Survival Case

Hepatic epithelioid hemangioendothelioma (HEHE) is a rare neoplasm of vascular origin. The clinical presentation of HEHE is variable, and the therapeutic criteria are still unclear since its natural history is unpredictable. A 53-year-old woman was admitted to our hospital because she had a 2.5-cm diameter nodule in the segment V of the liver. She had undergone segmental hepatectomy for solitary HEHE in segment VII 10 years before. There had been no recurrence for the 10 years after the first operation. The tumor was diagnosed as a new lesion of HEHE by percutaneous needle liver biopsy, and thereafter repeated hepatectomy was performed. HEHE seems to be resistant to chemotherapy and radiotherapy. Either surgical resection or orthotopic liver transplantation is generally recommended as a curative treatment for this disease. However, HEHE tends to be detected in multiple lesions, and localized disease is rare. Therefore, the chance of resection is very low. Some reports do not recommend local resection because of early aggressive tumor spread even after curative resection. We herein demonstrate a rare case of HEHE in a patient who underwent repeated hepatectomy for a solitary lesion and who survived for 17 years. It is concluded that surgical resection is one of the most effective treatments for a solitary form of HEHE.

Targeting the Hsp40/Hsp70 Chaperone Axis as a Novel Strategy to Treat Castration-Resistant Prostate Cancer

Castration-resistant prostate cancer (CRPC) is characterized by reactivation of androgen receptor (AR) signaling, in part by elevated expression of AR splice variants (ARv) including ARv7, a constitutively active, ligand binding domain (LBD)-deficient variant whose expression has been correlated with therapeutic resistance and poor prognosis. In a screen to identify small-molecule dual inhibitors of both androgen-dependent and androgen-independent AR gene signatures, we identified the chalcone C86. Binding studies using purified proteins and CRPC cell lysates revealed C86 to interact with Hsp40. Pull-down studies using biotinylated-C86 found Hsp40 present in a multiprotein complex with full-length (FL-) AR, ARv7, and Hsp70 in CRPC cells. Treatment of CRPC cells with C86 or the allosteric Hsp70 inhibitor JG98 resulted in rapid protein destabilization of both FL-AR and ARv, including ARv7, concomitant with reduced FL-AR- and ARv7-mediated transcriptional activity. The glucocorticoid receptor, whose elevated expression in a subset of CRPC also leads to androgen-independent AR target gene transcription, was also destabilized by inhibition of Hsp40 or Hsp70. In vivo, Hsp40 or Hsp70 inhibition demonstrated single-agent and combinatorial activity in a 22Rv1 CRPC xenograft model. These data reveal that, in addition to recognized roles of Hsp40 and Hsp70 in FL-AR LBD remodeling, ARv lacking the LBD remain dependent on molecular chaperones for stability and function. Our findings highlight the feasibility and potential benefit of targeting the Hsp40/Hsp70 chaperone axis to treat prostate cancer that has become resistant to standard antiandrogen therapy.Significance: These findings highlight the feasibility of targeting the Hsp40/Hsp70 chaperone axis to treat CRPC that has become resistant to standard antiandrogen therapy. Cancer Res; 78(14); 4022-35. ©2018 AACR.

The Tissue-Reconstructing Ability of Colon CSCs Is Enhanced by FK506 and Suppressed by GSK3 Inhibition

Cancer stem cells (CSC) are capable of reconstructing cancer tissues, are involved in both recurrence and metastasis, and contribute to therapeutic resistance. Therefore, elucidating the molecular mechanism in CSCs is important to successfully treat unresectable cancers. Previously, we observed that colon cancer stem-like cells can be induced from human colon cancer cell lines by retrovirally introducing OCT3/4, SOX2, and KLF4, and we have designated such cells as induced cancer stem cells (iCSC). In the current study, we used iCSCs to evaluate the molecular mechanism of colon CSCs and developed new methods to control them. The spheres that were derived in vitro from the iCSCs, but not those from parental cells, mimicked human colon cancer tissues in terms of their immunohistologic patterns; therefore, sphere-forming ability was assessed as a measure of the tissue-reconstructing ability of iCSCs. Interestingly, the calcineurin inhibitor FK506 enhanced the sphere-forming ability of iCSCs, whereas GSK3 inhibition by RNAi, CHIR99021, and valproic acid (VPA) impeded the sphere-forming ability and expansion of iCSCs. FK506 and GSK3 inhibition showed the opposite effect regarding the NFATc3 localization of iCSCs. These data reveal the crucial role that NFAT localization, as regulated by calcineurin and GSK3, plays in the tissue-reconstructing ability of colon cancer stem cells and the potential of GSK3 inhibitors, such as VPA, in colon cancer stem cell–targeting therapy. Implications: This study identifies signaling pathways that contribute to the tissue-reconstructing capacity of colon CSCs and suggests that clinically used drugs could be repurposed to improve unresectable colon cancers. Mol Cancer Res; 15(10); 1455–66. ©2017 AACR.

PET by MRI: Glucose Imaging by 13C-MRS without Dynamic Nuclear Polarization by Noise Suppression through Tensor Decomposition Rank Reduction

Metabolic reprogramming is one of the defining features of cancer and abnormal metabolism is associated with many other pathologies. Molecular imaging techniques capable of detecting such changes have become essential for cancer diagnosis, treatment planning, and surveillance. In particular, 18F-FDG (fluorodeoxyglucose) PET has emerged as an essential imaging modality for cancer because of its unique ability to detect a disturbed molecular pathway through measurements of glucose uptake. However, FDG-PET has limitations that restrict its usefulness in certain situations and the information gained is limited to glucose uptake only. 13C magnetic resonance spectroscopy theoretically has certain advantages over FDG-PET, but its inherent low sensitivity has restricted its use mostly to single voxel measurements. We show here a new method of imaging glucose metabolism in vivo that relies on a simple, but robust and efficient, post-processing procedure by the higher dimensional analog of singular value decomposition, tensor decomposition. Using this procedure, we achieve an order of magnitude increase in signal to noise in both dDNP and non-hyperpolarized non-localized experiments without sacrificing accuracy. In CSI experiments an approximately 30-fold increase was observed, enough that the glucose to lactate conversion indicative of the Warburg effect can be imaged without hyper-polarization with a time resolution of 12 s and an overall spatial resolution that compares favorably to 18F-FDG PET.

Direct and indirect assessment of cancer metabolism explored by MRI

Magnetic resonance‐based approaches to obtain metabolic information on cancer have been explored for decades. Electron paramagnetic resonance (EPR) has been developed to pursue metabolic profiling and successfully used to monitor several physiologic parameters such as pO2, pH, and redox status. All these parameters are associated with pathophysiology of various diseases. Especially in oncology, cancer hypoxia has been intensively studied because of its relationship with metabolic alterations, acquiring treatment resistance, or a malignant phenotype. Thus, pO2 imaging leads to an indirect metabolic assessment in this regard. Proton electron double‐resonance imaging (PEDRI) is an imaging technique to visualize EPR by using the Overhauser effect. Most biological parameters assessed in EPR can be visualized using PEDRI. However, EPR and PEDRI have not been evaluated sufficiently for clinical application due to limitations such as toxicity of the probes or high specific absorption rate. Hyperpolarized (HP) 13C MRI is a novel imaging technique that can directly visualize the metabolic profile. Production of metabolites of the HP 13C probe delivered to target tissue are evaluated in this modality. Unlike EPR or PEDRI, which require the injection of radical probes, 13C MRI requires a probe that can be physiologically metabolized and efficiently hyperpolarized. Among several methods for hyperpolarizing probes, dissolution dynamic nuclear hyperpolarization is a widely used technique for in vivo imaging. Pyruvate is the most suitable probe for HP 13C MRI because it is part of the glycolytic pathway and the high efficiency of pyruvate‐to‐lactate conversion is a distinguishing feature of cancer. Its clinical applicability also makes it a promising metabolic imaging modality. Here, we summarize the applications of these indirect and direct MR‐based metabolic assessments focusing on pO2 and pyruvate‐to‐lactate conversion. The two parameters are strongly associated with each other, hence the acquired information is potentially interchangeable when evaluating treatment response to oxygen‐dependent cancer therapies.

Wireless implantable coil with parametric amplification for in vivo electron paramagnetic resonance oximetric applications: ENOMOTO et al.

To develop an implantable wireless coil with parametric amplification capabilities for time‐domain electron paramagnetic resonance (EPR) spectroscopy operating at 300 MHz.

Abstract 2852: Monitoring the impact on metabolic flux in vivo of a newly developed LDH inhibitor using hyperpolarized 13C magnetic resonance spectroscopic imaging

[aim] Increased lactate production is a feature of many neoplasms, and Lactate Dehydrogenase A (LDH-A) plays a key role in conversion of pyruvate to lactate. LDHA inhibition, therefore, is considered to be a promising approach toward developing a new therapeutic strategy for cancer treatment focused on targeting cancer metabolism. Non-invasive imaging approaches able to monitor metabolic fluxes in vivo will be useful for this purpose. Hyperpolarized 13C Magnetic Resonance Imaging (MRI) has been well known as a valuable technology to investigate metabolic processes in tumor xenografts, allowing us to perform dynamic 13C-metabolic flux analysis in vivo. Use of [1-13C]pyruvate with this technology provides the ability to monitor LDHA activity in real time through dynamic observation of conversion of [1-13C]pyruvate to [1-13C]lactate. This study aimed to monitor drug efficacy of a newly developed LDH inhibitor (LDHI, obtained from National Cancer Institute Experimental Therapeutics Program, NExT) in a xenograft tumor model using 13C MRI technology with hyperpolarized 13C-labeled pyruvate. [Results] Hyperpolarized [1-13C]pyruvate MR studies were performed before and after LDHI administration to assess the impact on metabolic flux in vivo. Using hyperpolarized [1-13C]pyruvate MR Spectroscopy (MRS), we found that lactate production was significantly suppressed by LDHI administration in MiaPaca (a glycolytic pancreatic cancer cell line) tumors, as was the [1-13C]lactate to [1-13C]pyruvate ratio ([1-13C]-Lac/Pyr), which was calculated from the areas under the curves (AUC) using time-intensity data. This ratio decreased from 1.08 to 0.128 (88.1% decrease) 30 minutes after intravenous administration of the LDHI. In addition, hyperpolarized [1-13C]pyruvate MRS revealed that LDHI significantly suppressed lactate production in a dose dependent manner. Furthermore, Chemical Shift Imaging with 13C MRI demonstrated that the [1-13C]lactate signal in each voxel clearly decreased, compared to that before LDHI administration. The sum of [1-13C]lactate signals in the tumor region decreased after LDHI administration, resulting in a significant decrease in the tumor-specific [1-13C] Lac/Pyr ratio (1.463±0.31 before LDHI to 0.134±0.036 30 minutes after LDHI administration, a 90.67±2.56% decrease, n=3, p [Conclusions] These results indicate that hyperpolarized 13C-MRI is a useful method to evaluate on-target efficacy of novel LDH inhibitors in vivo, and this technique can be used to determine optimum dose and exposure time of the LDHI in the tumor region. The current method can be of great value in providing an in vivo pharmacodynamic biomarker for this novel anti-cancer therapeutic targeting deregulated tumor metabolism. Citation Format: Nobu Oshima, Shun Kishimoto, Kristin Beebe, Keita Saito, Kazutoshi Yamamoto, Jeffery Brender, Anastasia Sowers, Ganesha Rai, Bryan T. Mott, David J. Maloney, James B. Mitchell, Murali K. Cherukuri, Leonard M. Neckers. Monitoring the impact on metabolic flux in vivo of a newly developed LDH inhibitor using hyperpolarized 13C magnetic resonance spectroscopic imaging [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2852. doi:10.1158/1538-7445.AM2017-2852

Abstract 1898: microRNA-137/DCLK1 axis: A novel mechanism regulating tumorigenicity of colon cancer stem cell

Background: The understanding of colon cancer stem cell (CSC) biology is essential to developing new treatments, however, little is known about the molecular mechanisms underlying the acquisition of colon CSC properties. Furthermore, the similarity of the predisposition, including the surface markers, between colon CSCs and normal colon stem cells makes it difficult to develop a practical approach that targets colon CSCs. MicroRNA (miRNA) is one of the important factors regulating CSC properties. In addition, doublecortine-like kinase 1 (DCLK1), a microtubule-associated kinase, has been proposed to be a distinctive marker for colon CSCs. In the present study, we aimed to identify miRNAs that potentially target DCLK1 and unveil the role of the miRNA/DCLK1 axis in colon CSC properties. Material and Methods: Human colon cancer and normal colon specimens were dissociated into single cells and sorted by flow cytometry to separate the stem cell enriched population (EpCAM+/CD44+/CD66a-) and stained with anti-DCLK1 antibody. The expression profile of 384 miRNAs and the expression of DCLK1 in the colon CSC and normal colon stem cell populations were determined using a qRT-PCR. A luciferase activity assay and Western blotting were performed to evaluate the relationship between the miRNA and DCLK1. A lentiviral expression system was designed to investigate the miRNA phenotypes. We adopted an organoid assay and in vivo tumorigenicity assay to examine the influence of the miRNA on CSCs. Results: MiRNA-137 was highly expressed in the normal colon stem cell population whereas the DCLK1 mRNA expression was significantly upregulated in the colon CSC population. Actually, DCLK1-positive colon cancer cells were widely distributed in the colon cancer specimens, while DCLK1-positive epithelial cells were rarely detected in normal colon tissues, including the crypt bottoms. We confirmed that the activity of the luciferase gene linked to the 3’UTR of DCLK1 was decreased and that the protein level of DCLK1 was suppressed in the miRNA-137 transduced SW480 cells. The transduction of exogenous miRNA-137 suppressed the organoid development of colon cancer cells as well as shRNAs against DCLK1. The defect in organoid development by the transduction of miR-137 or shRNAs were substantially rescued by co-expression of the exsogenous DCLK1. Although miRNA-137 overexpression did not affect the organoid development of the normal intestine, miRNA-137 knockdown promoted the organoid development of normal colon cells. Xenograft tumor formation and growth were markedly suppressed in the miRNA-137-transduced SW480 cell-injected mice. Conclusion: These results suggest that miRNA-137 has the potential to suppress the tumorigenicity of colon CSCs through the inhibition of DCLK1 and that the dysregulation of the miRNA-137/DCLK1 axis plays an important role in colon CSCs. Citation Format: Masazumi Sakaguchi, Shigeo Hisamori, Nobu Oshima, Yoshiharu Sakai. microRNA-137/DCLK1 axis: A novel mechanism regulating tumorigenicity of colon cancer stem cell. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1898.