Reciprocal Interaction of Cancer Stem Cells of Cholangiocarcinoma with Macrophage

Cholangiocarcinoma is an aggressive type of liver cancer with few effective treatment options. Therefore, there is great need to better understand the biology of this malignancy to further development of novel treatment options. Cancer stem cells (CSCs) are thought to the underlying reason for cancer initiation, metastasis, and relapse. However, due to their elusive character and differences in identification among different types of cancer, it remains a challenge to study such cells. Additionally, characterization of the tumor microenvironment such as interactions with immune cells remain largely unknown. Here, we employ a fluorescent reporter system to track and isolate stem-like cancer cells of cholangiocarcinoma cell lines. Following verification of a stem-like signature (upregulated expression of stemness markers, resistance to chemotherapy, increased spheroid formation, and tumorigenesis capabilities despite inoculation of a small number of cells), we analyzed the interaction of these cells with macrophages via direct and indirect coculture assays. We noted direct coculturing increased stemness among CSC populations and induced both M1 (CD80 and HLA-DR) and M2 (CD163) tumor associated macrophage polarization. These studies suggest that there is a bi-directional crosstalk between macrophages and CSCs that promotes stemness renewal and tumor associated macrophage polarization.

miR-181c regulates MCL1 and cell survival in GATA2 deficient cells

GATA2 is a transcription factor critical for hematopoiesis. Germline mutations in GATA binding protein 2 (GATA2) led to haploinsufficiency, severe cytopenias of multiple cell lineages, susceptibility to infections and strong propensity to develop myelodysplastic syndrome, and acute myeloid leukemia. Mechanisms of progressive cytopenias remain unclear. MicroRNA (miRNA) represents a unique mechanism of post-transcriptional gene regulation. In this study, miRNA profiles were evaluated and eight miRNAs were found to be differentially expressed (≥2-fold, P ≤ 0.05) in patient-derived cell lines (N = 13) in comparison to controls (N = 10). miR-9, miR-181a-2-3p, miR-181c, miR-181c-3p, miR-486-3p, and miR-582 showed increased expression, whereas miR-223 and miR-424-3p showed decreased expression. Cell death assays indicated that miR-181c potently induces cell death in lymphoid (Ly-8 and SP-53) and myeloid (HL-60) cell lines. miR-181c was predicted to target myeloid cell leukemia (MCL)1, which was confirmed by transfection assays, resulting in significantly reduced MCL1 mRNA and decreased live cell numbers. Bone marrow analysis of 34 GATA2 patients showed significantly decreased cellularity, CD34-positive cells, monocytes, dendritic cells, NK cells, B cells, and B cell precursors in comparison to healthy controls (N = 29; P < 0.001 for each), which was accompanied by decreased levels of MCL1 (P < 0.05). GATA2 expression led to significant repression of miR-181c expression in transfection experiments. Conversely, knockdown of GATA2 led to increased miR-181c expression. These findings indicate that miR-181c expression is increased and MCL1 levels decreased in GATA2 deficiency cells, and that GATA2 represses miR-181c transcription. Increased miR-181c may contribute to elevated cell death and cytopenia in GATA2 deficiency potentially through down-regulation of MCL1.

The transcription factor c-Myb regulates CD8+ T cell stemness and antitumor immunity

Stem cells are maintained by transcriptional programs that promote self-renewal and repress differentiation. Here, we found that the transcription factor c-Myb was essential for generating and maintaining stem cells in the CD8+ T cell memory compartment. Following viral infection, CD8+ T cells lacking Myb underwent terminal differentiation and generated fewer stem cell-like central memory cells than did Myb-sufficient T cells. c-Myb acted both as a transcriptional activator of Tcf7 (which encodes the transcription factor Tcf1) to enhance memory development and as a repressor of Zeb2 (which encodes the transcription factor Zeb2) to hinder effector differentiation. Domain-mutagenesis experiments revealed that the transactivation domain of c-Myb was necessary for restraining differentiation, whereas its negative regulatory domain was critical for cell survival. Myb overexpression enhanced CD8+ T cell memory formation, polyfunctionality and recall responses that promoted curative antitumor immunity after adoptive transfer. These findings identify c-Myb as a pivotal regulator of CD8+ T cell stemness and highlight its therapeutic potential.

Targeting Notch1 and IKKα Enhanced NF-κB Activation in CD133+ Skin Cancer Stem Cells

Cancer stem-like cells are hypothesized to be the major tumor-initiating cell population of human cutaneous squamous cell carcinoma (cSCC), but the landscape of molecular alterations underpinning their signaling and cellular phenotypes as drug targets remains undefined. In this study, we developed an experimental pipeline to isolate a highly enriched CD133⁺CD31^-CD45^-CD61^-CD24^- (CD133⁺) cell population from primary cSCC specimens by flow cytometry. The CD133⁺ cells show enhanced stem-like phenotypes, which were verified by spheroid and colony formation in vitro and tumor generation in vivo Gene expression profiling of CD133^+/- cells was compared and validated, and differentially expressed gene signatures and top pathways were identified. CD133⁺ cells expressed a repertoire of stemness and cancer-related genes, including NOTCH and NOTCH1-mediated NF-κB pathway signaling. Other cancer-related genes from WNT, growth factor receptors, PI3K/mTOR, STAT pathways, and chromatin modifiers were also identified. Pharmacologic and genetic targeting of NOTCH1, IKKα, RELA, and RELB modulated NF-κB transactivation, the CD133⁺ population, and cellular and stemness phenotypes. Immunofluorescent staining confirmed colocalization of CD133⁺ and IKKα expression in SCC tumor specimens. Our functional, genetic, and pharmacologic studies uncovered a novel linkage between NOTCH1, IKKα, and NF-κB pathway activation in maintaining the CD133⁺ stem SCC phenotypes. Studies investigating markers of activation and modulators of NOTCH, IKK/NF-κB, and other pathways regulating these cancer stem gene signatures could further accelerate the development of effective therapeutic strategies to treat cSCC recurrence and metastasis. Mol Cancer Ther; 17(9); 2034-48. ©2018 AACR.