Downregulation of beta-microglobulin to diminish T-lymphocyte lysis of non-syngeneic cell sources of engineered heart tissue constructs

A Novel Tongue Squamous Cell Carcinoma Cell Line Escapes from Immune Recognition due to Genetic Alterations in HLA Class I Complex

Immune checkpoint inhibitors (ICI) have made progress in the field of anticancer treatment, but a certain number of PD-L1 negative OSCC patients still have limited benefits from ICI immuno-therapy because of primary immune evasion due to immunodeficiency. However, in existing human OSCC cell lines, cell models that can be used to study immunodeficiency have not been reported. The objective of this study was to establish a PD-L1 negative OSCC cell line, profile whether the presence of mutated genes is associated with immune deficiency, and explore its influence on the immune recognition of CD8⁺ T cells in vitro. Here, we established a novel tongue SCC cell line (WU-TSC-1), which escapes from immune recognition by antigen presentation defects. This cell line was from a female patient who lacked typical causative factors. The expression of PD-L1 was negative in the WU-TSC-1 primary tumor, transplanted tumor, cultured cells and lipopolysaccharide stimulation. Whole exome sequencing (WES) revealed that WU-TSC-1 harbored missense mutations, loss of copy number and structural variations in human leukocyte antigen (HLA) class I/II genes. The tumor mutation burden (TMB) score was high at 292.28. In addition, loss of heterozygosity at beta-2-microglobulin (B2M)-a component of all HLA class I complex allotypes-was detected. Compared with the commonly used OSCC cell lines, genetic alterations in HLA class I and B2M impeded the proteins' translation and inhibited the activation and killing effect of CD8⁺ T cells. In all, the WU-TSC-1 cell line is characterized by genetic variations and functional defects of the HLA class I complex, leading to escape from recognition by CD8⁺ T cells.

Building Valveless Impedance Pumps From Biological Components: Progress and Challenges

Valveless pumping based on Liebau mechanism entails asymmetrical positioning of the compression site relative to the attachment sites of the pump's elastic segment to the rest of the circuit. Liebau pumping is believed to play a key role during heart development and be involved in several other physiological processes. Until now studies of Liebau pump have been limited to numerical analyses, in silico modeling, experiments using non-biological elements, and a few indirect in vivo measurements. This review aims to stimulate experimental efforts to build Liebau pumps using biologically compatible materials in order to encourage further exploration of the fundamental mechanisms behind valveless pumping and its role in organ physiology. The covered topics include the biological occurrence of Liebau pumps, the main differences between them and the peristaltic flow, and the potential uses and body sites that can benefit from implantable valveless pumps based on Liebau principle. We then provide an overview of currently available tools to build such pumps and touch upon limitations imposed by the use of biological components. We also talk about the many variables that can impact Liebau pump performance, including the concept of resonant frequencies, the shape of the flowrate-frequency relationship, the flow velocity profiles, and the Womersley numbers. Lastly, the choices of materials to build valveless impedance pumps and possible modifications to increase their flow output are briefly discussed.

Novel reference genes in colorectal cancer identify a distinct subset of high stage tumors and their associated histologically normal colonic tissues

Background

Reference genes are often interchangeably called housekeeping genes due to 1) the essential cellular functions their proteins provide and 2) their constitutive expression across a range of normal and pathophysiological conditions. However, given the proliferative drive of malignant cells, many reference genes such as beta-actin (ACTB) and glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) which play critical roles in cell membrane organization and glycolysis, may be dysregulated in tumors versus their corresponding normal controls

Methods

Because Next Generation Sequencing (NGS) technology has several advantages over hybridization-based technologies, such as independent detection and quantitation of transcription levels, greater sensitivity, and increased dynamic range, we evaluated colorectal cancers (CRC) and their histologically normal tissue counterparts by NGS to evaluate the expression of 21 “classical” reference genes used as normalization standards for PCR based methods. Seventy-nine paired tissue samples of CRC and their patient matched healthy colonic tissues were subjected to NGS analysis of their mRNAs.

Results

We affirmed that 17 out of 21 classical reference genes had upregulated expression in tumors compared to normal colonic epithelial tissue and dramatically so in some cases. Indeed, tumors were distinguished from normal controls in both unsupervised hierarchical clustering analyses (HCA) and principal component analyses (PCA). We then identified 42 novel potential reference genes with minimal coefficients of variation (CV) across 79 CRC tumor pairs. Though largely consistently expressed across tumors and normal control tissues, a subset of high stage tumors (HSTs) as well as some normal tissue samples (HSNs) located adjacent to these HSTs demonstrated dysregulated expression, thus identifying a subset of tumors with a potentially distinct and aggressive biological profile.

Conclusion

While classical CRC reference genes were found to be differentially expressed between tumors and normal controls, novel reference genes, identified via NGS, were more consistently expressed across malignant and normal colonic tissues. Nonetheless, a subset of HST had profound dysregulation of such genes as did many of the histologically normal tissues adjacent to such HSTs, indicating that the HSTs so distinguished may have unique biological properties and that their histologically normal tissues likely harbor a small population of microscopically undetected but metabolically active tumors.

Electronic supplementary material

The online version of this article (10.1186/s12881-019-0867-y) contains supplementary material, which is available to authorized users.

HLA Class I Depleted hESC as a Source of Hypoimmunogenic Cells for Tissue Engineering Applications

BACKGROUND

Rapidly improving protocols for the derivation of autologous cells from stem cell sources is a welcome development. However, there are many circumstances when off-the-shelf universally immunocompatible cells may be needed. Embryonic stem cells (ESCs) provide a unique opportunity to modify the original source of differentiated cells to minimize their rejection by nonautologous hosts.

HYPOTHESIS

Immune rejection of nonautologous human embryonic stem cell (hESC) derivatives can be reduced by downregulating human leukocyte antigen (HLA) class I molecules, without affecting the ability of these cells to differentiate into specific lineages.

METHODS AND RESULTS

Beta-2-microglobulin (B2M) expression was decreased by lentiviral transduction using human anti-HLA class I light-chain B2M short hairpin RNA. mRNA levels of B2M were decreased by 90% in a RUES2-modified hESC line, as determined by quantitative real time-polymerase chain reaction analysis. The transduced cells were selected under puromycin pressure and maintained in an undifferentiated state. The latter was confirmed by Oct4 and Nanog expression, and by the formation of characteristic round-shaped colonies. B2M downregulation led to diminished HLA-I expression on the cell surface, as determined by flow cytometry. When used as target cells in a mixed lymphocyte reaction assay, transduced hESCs and their differentiated derivatives did not stimulate allogeneic T-cell proliferation. Using a cardiac differentiation protocol, transduced hESCs formed a confluent layer of cardiac myocytes and maintained a low level of B2M expression. Transduced hESCs were also successfully differentiated into a hepatic lineage, validating their capacity to differentiate into multiple lineages.

CONCLUSIONS

HLA-I depletion does not preclude hESC differentiation into cardiac or hepatic lineages. This methodology can be used to engineer tissue from nonautologous hESC sources with improved immunocompatibility.