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A recent hypothesis for cancer chemoresistance posits that cytotoxic survival of a subpopulation of tumor progenitors drives the propagation of recurrent disease, underscoring the need for new therapeutics that target such primitive cells. To discover such novel compounds active against drug-resistant ovarian cancer, we identified a subset of chemoresistant ovarian tumor cells fulfilling current definitions of cancer-initiating cells from cell lines and patient tumors using multiple stemness phenotypes, including the expression of stem cell markers, membrane dye efflux, sphere formation, potent tumorigenicity, and serial tumor propagation. We then subjected such stem-like ovarian tumor-initiating cells (OTIC) to high-throughput drug screening using more than 1,200 clinically approved drugs. Of 61 potential compounds preliminarily identified, more stringent assessments showed that the antihelmintic niclosamide selectively targets OTICs in vitro and in vivo. Gene expression arrays following OTIC treatment revealed niclosamide to disrupt multiple metabolic pathways affecting biogenetics, biogenesis, and redox regulation. These studies support niclosamide as a promising therapy for ovarian cancer and warrant further preclinical and clinical evaluation of this safe, clinically proven drug for the management of this devastating gynecologic malignancy.

SummaryMesenchymal stromal cells (MSCs) are multilineage progenitors with immunomodulatory properties, including expansion of immunomodulatory leukocytes such as regulatory T lymphocytes (Tregs) and tolerogenic dendritic cells. We report that human MSCs can expand CD14−CD11b+CD33+ human myeloid-derived suppressor cells (MDSCs). MSC-expanded MDSCs suppress allogeneic lymphocyte proliferation, express arginase-1 and inducible nitric oxide synthase, and increase the number of Tregs. This expansion occurs through the secretion of hepatocyte growth factor (HGF), with effects replicated by adding HGF singly and abrogated by HGF knockdown in MSCs. In wild-type mice, the liver, which secretes high levels of HGF, contains high numbers of Gr-1+CD11b+ MDSCs, and injection of HGF into mice significantly increases the number of MDSCs. Expansion of MDSCs by MSC-secreted HGF involves c-Met (its receptor) and downstream phosphorylation of STAT3, a key factor in MDSC expansion. Our data further support the strong immunomodulatory nature of MSCs and demonstrate the role of HGF, a mitogenic molecule, in the expansion of MDSCs.

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In this study, we explore a potential vaccine for human papillomavirus (HPV)-induced tumors, using heat shock protein as an adjuvant, a peptide vaccine for safety, and adeno-associated virus ( Cervical carcinoma remains one of the most common malignancies worldwide, with 500,000 new cases diagnosed each year (5) and 200,000 cervical cancer deaths annually (21). Human papillomavirus type 16 (HPV-16) is the predominant etiologic agent of cervical cancer and carries three transforming oncogenes, E5, E6, and E7 (10,20,45). Their products are thus unique tumor antigens and can be ideally used as tumor vaccines (7). Because E6 and E7 oncoproteins are consistently retained and expressed, the E6 and E7 oncogenes become more attractive targets for T-cell-based immunotherapy of cervical cancer. Evidence for the value of HPV antigen-directed immunotherapy against cervical cancer comes from the experimental and natural papillomavirus-associated tumors that can be controlled by immunization with E7 antigen. Previous studies have used different modes of immunization, such as (i) recombinant E7 vaccinia viruses (2,3,16,24,28,42), (ii) syngeneic cells transfected with E7 (8, 9), (iii) E7 proteinpulsed dendritic cells (12, 37), (iv) peptides corresponding to a cytotoxic T-lymphocyte (CTL) epitope in E7 with incomplete Freund's adjuvant (13), (v) E7 vaccine based on papillomavirus-like particles (17,25,31), and (vi) Salmonella enterica serovar Typhimurium expressing E7 epitope inserted into hepatitis B virus core (26). These studies demonstrate that CTLs are likely to be the most effective immunological effector mechanisms.Adeno-associated virus (AAV), a single-stranded virus, has been studied as a vector for gene therapy (29, 41). Classified as a defective human parvovirus, AAV has many natural features that are attractive for a human gene therapy vector, such as nonpathogenicity, targeted integrating capability, and a broad host range (human, simian, murine, canine, and avian). In sharp contrast to other viral vectors that have been used in vaccination, such as vaccinia virus or adenovirus, AAV vectors do not express any viral genes. The only viral DNA that must be included in an AAV vector is the 145-bp inverted terminal repeat. Since naked DNA is used for immunization, the only gene expressed by AAV vectors is that for the antigen itself.Since HPV-16 E7 is a transforming oncoprotein (20), dangerous side effects such as transformation are not anticipated with a protein vaccine. Peptide vaccination with a CTL epitope to prevent the outgrowth of a tumor is a safe and effective immunotherapeutic method (13). However, a peptide vaccine combined with a toxic adjuvant such as incomplete Freund's adjuvant sometimes can lead to rapid tumor growth through specific T-cell tolerance induction (36). Recently, Mycobacterium tuberculosis heat shock protein 70 (hsp70) has been used as an adjuvant-free carrier to stimulate the humoral and cellular response to a full-length human immunodeficiency virus p24 (33) that is covalently linked to hsp...

Monocytes are a population of leukocytes that terminally differentiate into macrophages and DCs. Whereas these differentiated progeny have inflammatory and resident--which are more immunomodulatory--phenotypes, less has been reported on the plasticity of monocytes themselves. We found that MSCs, a population of somatic stem cells, can rapidly induce human and murine monocytes through secretion of HGF to acquire an immunomodulatory phenotype to suppress T cell effector function. MSCs are multilineage postnatal progenitor cells with strong immunomodulatory effects toward T lymphocytes, NK lymphocytes, and DCs, but less is known regarding their interactions with monocytes. We found that CD14(+) human monocytes express c-Met, the receptor for HGF, and both depletion of HGF-treated CD14(+) monocytes and knockdown of HGF secretion in MSCs abrogate the suppression of anti-CD3/28-activated T cell proliferation. HGF-treated monocytes remain undifferentiated and can alter activated T cell cytokine expression from a Th1 toward Th2 profile. Moreover, monocytes cocultured with MSCs or treated with HGF alone can produce high levels of IL-10, a potent immunomodulatory cytokine. Injection of HGF to WT mice also results in an increase in IL-10(+)-expressing monocytes from the spleen, a known reservoir for circulating monocytes. Mechanistically, HGFs modulate IL-10 production in monocytes through the ERK1/2 pathway. Our data demonstrate further the pleomorphic nature of MSC immunomodulation, as well as highlight the important role of immunomodulatory monocytes in altering T cell effector function.

The broad immunomodulatory properties of human mesenchymal stem cells (MSCs) have allowed for wide application in regenerative medicine as well as immune/ inflammatory diseases, including unmatched allogeneic use. The novel coronavirus disease COVID-19 has unleashed a pandemic in record time accompanied by an alarming mortality rate mainly due to pulmonary injury and acute respiratory distress syndrome. Because there are no effective preventive or curative therapies currently, MSC therapy (MSCT) has emerged as a possible candidate despite the lack of preclinical data of MSCs for COVID-19. Interestingly, MSCT preclinical data specifically on immune/inflammatory disorders of the lungs were among the earliest to be reported in 2003, with the first clinical use of MSCT for graft-vs-host disease reported in 2004. Since these first reports, preclinical data showing beneficial effects of MSC immunomodulation have accumulated substantially, and as a consequence, over a third of MSCT clinical trials now target immune/inflammatory diseases. There is much preclinical evidence for MSCT in noninfectious-including chronic obstructive pulmonary disease, asthma, and idiopathic pulmonary fibrosis-as well as infectious bacterial immune/inflammatory lung disorders, with data generally demonstrating therapeutic effects; however, for infectious viral pulmonary conditions, the preclinical evidence is more scarce with some inconsistent outcomes. In this article, we review the mechanistic evidence for clinical use of MSCs in pulmonary immune/inflammatory disorders, and survey the ongoing clinical trials-including for COVID-19-of MSCT for these diseases, with some perspectives and comment on MSCT for COVID-19.

Compelling evidence suggests that infiltrating CD4+ type I helper T (Th1) cells in the pancreatic islets play a pivotal role in the progression of diabetes in non-obese diabetic (NOD) mice. We demonstrate in the present report that a butanol fraction of B. pilosa suppressed the development of diabetes, helped maintain levels of blood sugar and insulin in NOD mice in a dose-dependent manner and elevated the serum IgE levels regulated by Th2 cytokines in NOD mice. Moreover, the butanol fraction inhibited the differentiation of naive helper T (Th0) cells into Th1 cells but enhanced their transition into type II helper T (Th2) cells using an in vitro T cell differentiation assay. Two polyacetylenic compounds, 2-beta-D-glucopyranosyloxy-1-hydroxy-5(E)-tridecene-7,9,11-triyne and 3-beta-D-glucopyranosyloxy-1-hydroxy-6(E)-tetradecene-8,10,12-triyne, identified from the butanol fraction also prevented the onset of diabetes like the butanol fraction. The latter compound showed a stronger activity for T cell differentiation than the former. In summary, the butanol fraction of B. pilosa and its polyacetylenes can prevent diabetes plausibly via suppressing the differentiation of Th0 cells into Th1 cells and promoting that of Th0 cells into Th2 cells.