The diverse composition of mammalian tissues poses challenges for understanding the cell–cell interactions required for organ homeostasis and how spatial relationships are perturbed during disease. Existing methods such as single-cell genomics, lacking a spatial context, and traditional immunofluorescence, capturing only two to six molecular features, cannot resolve these issues. Imaging technologies have been developed to address these problems, but each possesses limitations that constrain widespread use. Here we report a method that overcomes major impediments to highly multiplex tissue imaging. “Iterative bleaching extends multiplexity” (IBEX) uses an iterative staining and chemical bleaching method to enable high-resolution imaging of >65 parameters in the same tissue section without physical degradation. IBEX can be employed with various types of conventional microscopes and permits use of both commercially available and user-generated antibodies in an “open” system to allow easy adjustment of staining panels based on ongoing marker discovery efforts. We show how IBEX can also be used with amplified staining methods for imaging strongly fixed tissues with limited epitope retention and with oligonucleotide-based staining, allowing potential cross-referencing between flow cytometry, cellular indexing of transcriptomes and epitopes by sequencing, and IBEX analysis of the same tissue. To facilitate data processing, we provide an open-source platform for automated registration of iterative images. IBEX thus represents a technology that can be rapidly integrated into most current laboratory workflows to achieve high-content imaging to reveal the complex cellular landscape of diverse organs and tissues.
Mesothelioma is an aggressive cancer of the serous membranes with poor prognosis despite combination therapy consisting of surgery, radiotherapy, and platinum-based chemotherapy. Targeted therapies, including immunotherapies, have reported limited success, suggesting the need for additional therapeutic targets. This study investigates a potential new therapeutic target, gC1qR/HABP1/p32 (gC1qR), which is overexpressed in all morphologic subtypes of mesothelioma. gC1qR is a complement receptor that is associated with several cellular functions, including cell proliferation and angiogenesis. In vitro and in vivo experiments were conducted to test the hypothesis that targeting gC1qR with a specific gC1qR monoclonal antibody 60.11 reduces mesothelioma tumor growth, using the biphasic mesothelioma cell line MSTO-211H (MSTO). In vitro studies demonstrate cell surface and extracellular gC1qR expression by MSTO cells, and a modest 25.3 ± 1.8% (n = 4) reduction in cell proliferation by the gC1qR blocking 60.11 antibody. This inhibition was specific for targeting the C1q binding domain of gC1qR at aa 76-93, as a separate monoclonal antibody 74.5.2, directed against amino acids 204-218, had no discernable effect. In vivo studies, using a murine orthotopic xenotransplant model, demonstrated an even greater reduction in MSTO tumor growth (50% inhibition) in mice treated with the 60.11 antibody compared to controls. Immunohistochemical studies of resected tumors revealed increased cellular apoptosis by caspase 3 and TUNEL staining, in 60.11 treated tumors compared to controls, as well as impaired angiogenesis by decreased CD31 staining. Taken together, these data identify gC1qR as a potential new therapeutic target against mesothelioma with both antiproliferative and antiangiogenic properties.
The immunopathological functions associated with human C1q are still growing in terms of novelty, diversity, and pathologic relevance. It is, therefore, not surprising that C1q is being recognized as an important molecular bridge between innate and adaptive immunity. The secret of this functional diversity, in turn, resides in the elegant but complex structure of the C1q molecule, which is assembled from three distinct gene products: A, B, and C, each of which has evolved from a separate and unique ancestral gene template. The C1q molecule is made up of 6A, 6B, and 6C polypeptide chains, which are held together through strong covalent and non-covalent bonds to form the 18-chain, bouquet-of-flower-like protein that we know today. The assembled C1q protein displays at least two distinct structural and functional regions: the collagen-like region (cC1q) and the globular head region (gC1q), each being capable of driving a diverse range of ligand- or receptor-mediated biological functions. What is most intriguing, however, is the observation that most of the functions appear to be predominantly driven by the A-chain of the molecule, which begs the question: what are the evolutionary modifications or rearrangements that singularly shaped the primordial A-chain gene to become a pluripotent and versatile component of the intact C1q molecule? Here, we revisit and discuss some of the known unique structural and functional features of the A-chain, which may have contributed to its versatility.
There is robust experimental data, which show that C1q and gC1qR play a pro- as well as anti-proliferative role in cancer. This opposing role in turn depends on whether each molecule is expressed on the cell surface or pericellular milieu. The aim of the present studies was therefore to more closely examine the functions of soluble and membrane forms of gC1qR and C1q using the SkBr3 cell line as a model for breast cancer. Our results show that: (1) In addition to gC1qR and cC1qR, SkBr3 cells express membrane C1q, and these molecules appear to be co-localized with each other as well as with fibrinogen (FGN) and vitronectin (VN). (2) Co-culture of SkBr3 cells with either purified C1q or with pAb directed against the gC1qR site on the A-chain of gC1q (ghA) resulted in a time-dependent inhibition of cell growth. (3) Co-culture of SkBr3 cells with individual C1q head modules-–ghA, ghB and ghC–showed significant inhibition, with the inhibitory hierarchy being ghA>ghC >ghB. (4) While SkBr3 cells do not secrete C1q, they are able to secrete gC1qR, and the latter in turn is able to negate the anti-proliferative effect of exogenously added C1q supporting the postulate that gC1qR secreted into the tumor cell microenvironment serves as an important molecular checkpoint. Collectively, the data show that both membrane-associated gC1qR and C1q on their own are pro-proliferative. Whereas the proliferative function of gC1qR can be abrogated by blockade of its C1q binding site, the proliferative function of C1q can be abrogated by blockade of its gh domains with specific antibodies indicating therefore that the pro-proliferative function of C1q resides in the its gh domains, with the ghA domain playing a central role.
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