Effect of membrane‑bound complement regulatory proteins on tumor cell sensitivity to complement‑dependent cytolysis triggered by heterologous expression of the α‑gal xenoantigen

Abstract

Engineering malignant cells to express a heterologous α-gal antigen can induce heterograft hyperacute rejection, resulting in complement-dependent cytolysis (CDC) of tumor cells, which has been considered as a novel strategy for antitumor therapy. A549 cells engineered to express Galα1-3Galβ1-4GlcNAc-R (α-gal) epitope exhibited strong resistance to CDC treated by normal human serum (NHS) in a previous study. We hypothesized that the expression of membrane-bound complement regulatory proteins (mCRPs) decay accelerating factor (CD55) and protectin (CD59) influenced the efficacy of the α-gal/NHS-mediated antitumor effect to tumor cells in vitro. The present study confirmed that A549 cells expressed high levels of CD55 and CD59, whereas Lovo cells expressed relatively low levels of these proteins. A549 and Lovo cells transfected with plasmids containing or lacking the α-gal epitope were evaluated for their susceptibility to CDC by NHS and detected using a trypan blue exclusion assay. α-gal-expressing Lovo (Lovo-GT) cells were almost completely killed by α-gal-mediated CDC following incubation with 50% NHS, whereas no cytolysis was observed in α-gal expressing A549 (A549-GT) cells. Abrogating CD55 and CD59 function from A549-GT cells by various concentrations of phosphatidylinositol-specific phospholipase C (PI-PLC) or blocking antibodies increased the susceptibility of cells to CDC, and the survival rate decreased significantly comparing to the controls (P<0.05). The findings of the present study indicated that using the α-gal/NHS system to eliminate tumor cells via inducing the complement cascade reaction might represent a feasible approach for the treatment of cancer. However, high levels of mCRP expression may limit the efficacy of this approach. Therefore, an improved efficacy of cancer cell killing may be achieved by combining strategies of heterologous α-gal expression and mCRP downregulation.

Role of B-Cell Lymphoma 2 Ovarian Killer (BOK) in Acute Toxicity of Human Lung Epithelial Cells Caused by Cadmium Chloride

“…The cells (50 μl) were mixed with the same volume of 0.4% trypan blue. The numbers of stained cells were counted in a hemocytometer under a light microscope [22].…”

AGI-134: a fully synthetic α-Gal glycolipid that converts tumors into in situ autologous vaccines, induces anti-tumor immunity and is synergistic with an anti-PD-1 antibody in mouse melanoma models

“…We have shown that AGI-134 mediates CDC effectively in both SW480 and A549 human cancer cells. Interestingly, the latter cell line was more resistant to CDC, i.e., more AGI-134 was necessary to facilitate A549 cell lysis by human serum which may be due to higher expression of complement regulatory proteins such as CD55 and CD59 [61]. In addition, complement activation has a number of effects that actively link innate and adaptive immunity [51, 52].…”

Membrane-Bound Complement Regulatory Proteins in Breast Cancer: Are They Best Therapeutic Targets?

“…Following the evidence that HER2-positive patients who did not respond to trastuzumab had elevated CD55 expression, CD55 and CD59 have been reported to be involved in resistance to trastuzumab or pertuzumab. Mechanistically, HER2 antibodies (trastuzumab or pertuzumab) contain IgG1 Fc that induces CDC in cancer cells by activating the classical complement pathway, thus canonical CD55 and CD59 signaling allow blockade of HER2 antibody-mediated complement regulation [13,70]. This was studied in breast cancer cell lines by blocking CD55/CD59 activity using mAbs, modulating their expression via phosphatidylinositol-specific phospholipase C (PI-PLC) and silencing their expression using short hairpin RNA (shRNA).…”

“…A significantly increased tumor-infiltrating ICOSL+ B population was identified after neoadjuvant chemotherapy in samples from breast cancer patients. It has been described that tumor cell death induced by chemotherapy activates the complement system via the alternative pathway through phosphatidylserine (PS) and is responsible for inducing ICOSL+ B cells via complement receptor type 2 (CR2) [70]. CR2 recognizes complement C3 cleavage products (C3b, iC3b, and C3c) bound to antigens and acts with the B cell antigen receptor (BCR) to lower the activation threshold and overcome B cell anergy [74].…”