MYB bi-allelic targeting abrogates primitive clonogenic progenitors while the emergence of primitive blood cells is not affected

Human anti-PSCA CAR macrophages possess potent antitumor activity against pancreatic cancer

Due to the limitations of autologous chimeric antigen receptor (CAR)-T cells, alternative sources of cellular immunotherapy, including CAR macrophages, are emerging for solid tumors. Human induced pluripotent stem cells (iPSCs) offer an unlimited source for immune cell generation. Here, we develop human iPSC-derived CAR macrophages targeting prostate stem cell antigen (PSCA) (CAR-iMacs), which express membrane-bound interleukin (IL)-15 and truncated epidermal growth factor receptor (EGFR) for immune cell activation and a suicide switch, respectively. These allogeneic CAR-iMacs exhibit strong antitumor activity against human pancreatic solid tumors in vitro and in vivo, leading to reduced tumor burden and improved survival in a pancreatic cancer mouse model. CAR-iMacs appear safe and do not exhibit signs of cytokine release syndrome or other in vivo toxicities. We optimized the cryopreservation of CAR-iMac progenitors that remain functional upon thawing, providing an off-the-shelf, allogeneic cell product that can be developed into CAR-iMacs. Overall, our preclinical data strongly support the potential clinical translation of this human iPSC-derived platform for solid tumors, including pancreatic cancer.

The genesis of human hematopoietic stem cells

Developmental hematopoiesis consists of multiple, partially overlapping hematopoietic waves that generate the differentiated blood cells required for embryonic development while establishing a pool of undifferentiated hematopoietic stem cells (HSCs) for postnatal life. This multilayered design in which active hematopoiesis migrates through diverse extra and intraembryonic tissues has made it difficult to define a roadmap for generating HSCs vs non-self-renewing progenitors, especially in humans. Recent single-cell studies have helped in identifying the rare human HSCs at stages when functional assays are unsuitable for distinguishing them from progenitors. This approach has made it possible to track the origin of human HSCs to the unique type of arterial endothelium in the aorta-gonad-mesonephros region and document novel benchmarks for HSC migration and maturation in the conceptus. These studies have delivered new insights into the intricate process of HSC generation and provided tools to inform the in vitro efforts to replicate the physiological developmental journey from pluripotent stem cells via distinct mesodermal and endothelial intermediates to HSCs.

New insights into the characteristics of DRAK2 and its role in apoptosis: From molecular mechanisms to clinically applied potential

As a member of the death-associated protein kinase (DAPK) family, DAP kinase-associated apoptosis-inducing kinase 2 (DRAK2) performs apoptosis-related functions. Compelling evidence suggests that DRAK2 is involved in regulating the activation of T lymphocytes as well as pancreatic β-cell apoptosis in type I diabetes. In addition, DRAK2 has been shown to be involved in the development of related tumor and non-tumor diseases through a variety of mechanisms, including exacerbation of alcoholic fatty liver disease (NAFLD) through SRSF6-associated RNA selective splicing mechanism, regulation of chronic lymphocytic leukemia and acute myeloid leukemia, and progression of colorectal cancer. This review focuses on the structure, function, and upstream pathways of DRAK2 and discusses the potential and challenges associated with the clinical application of DRAK2-based small-molecule inhibitors, with the aim of advancing DRAK2 research.

Germline competent mesoderm: the substrate for vertebrate germline and somatic stem cells?

In vitro production of tissue-specific stem cells [e.g. haematopoietic stem cells (HSCs)] is a key goal of regenerative medicine. However, recent efforts to produce fully functional tissue-specific stem cells have fallen short. One possible cause of shortcomings may be that model organisms used to characterize basic vertebrate embryology (Xenopus, zebrafish, chick) may employ molecular mechanisms for stem cell specification that are not conserved in humans, a prominent example being the specification of primordial germ cells (PGCs). Germ plasm irreversibly specifies PGCs in many models; however, it is not conserved in humans, which produce PGCs from tissue termed germline-competent mesoderm (GLCM). GLCM is not conserved in organisms containing germ plasm, or even in mice, but understanding its developmental potential could unlock successful production of other stem cell types. GLCM was first discovered in embryos from the axolotl and its conservation has since been demonstrated in pigs, which develop from a flat-disc embryo like humans. Together these findings suggest that GLCM is a conserved basal trait of vertebrate embryos. Moreover, the immortal nature of germ cells suggests that immortality is retained during GLCM specification; here we suggest that the demonstrated pluripotency of GLCM accounts for retention of immortality in somatic stem cell types as well.

This article has an associated Future Leaders to Watch interview with the author of the paper.

Summary: Recent findings that germline and stem cell specification may differ between species may have important implications for regenerative medicine and the future of stem cell biology.

Recapitulative haematopoietic development of human pluripotent stem cells in the absence of exogenous haematopoietic cytokines

To improve the recapitulative quality of human pluripotent stem cell (hPSC) differentiation, we removed exogenous haematopoietic cytokines from the defined differentiation system. Here, we show that endogenous stimuli and VEGF are sufficient to induce robust hPSC-derived haematopoiesis, intensive generation of haematopoietic progenitors, maturation of blood cells and the emergence of definitive precursor cells including those that phenotypically identical to early human embryonic haematopoietic stem cells (HSCs). Moreover, the cytokine-free system produces significantly higher numbers of haematopoietic progenitors compared to the published protocols. The removal of cytokines revealed a broad developmental potential of the early blood cells, stabilized the hPSC-derived definitive precursors and led to spontaneous activation of inflammatory signalling. Our cytokine-free protocol is simple, efficient, reproducible and applicable for embryonic stem cells (ESCs) and induced PSCs. The spectrum of recapitulative features of the novel protocol makes the cytokine-free differentiation a preferred model for studying the early human haematopoietic development.