The initial immune reaction to a new tumor antigen is always stimulatory and probably necessary for the tumor's growth

The early antitumor immune response is necessary for tumor growth: Re-visiting Prehn's hypothesis in the human melanoma system

Early events responsible of tumor growth in patients with a normal immune system are poorly understood. Here, we discuss, in the context of human melanoma, the Prehn hypothesis according to which a weak antitumor immune response may be required for tumor growth before weakly or non-immunogenic tumor cell subpopulations are selected by the immune system.

Tumor-associated macrophages in classical Hodgkin lymphoma: hormetic relationship to outcome

Commonly attributed to the prevalence of M2 macrophages, tumor-associated macrophages (TAM) are linked to poor outcome in Hodgkin lymphoma (HL). MYC is supposed to control the expression of M2-specific genes in macrophages, and deficiency in MYC-positive macrophages inhibits tumor growth in mouse models. To verify this hypothesis for HL, seventy-six samples were subjected to immunohistochemical double staining using CD68 or CD163 macrophage-specific antibodies and a reagent detecting MYC. For each cell population, labelled cells were grouped according to low, intermediate and high numbers and related to disease-free survival (DFS) and overall survival (OS). MYC+ cells accounted for 21% and 18% of CD68+ and CD163+ cells, respectively. Numbers of MYC- macrophages were significantly higher in EBV+ cases while no differences were observed for MYC+ macrophages between EBV+ and EBV- cases. Cases with highest numbers of macrophages usually showed worst DFS and OS. In most scenarios, intermediate numbers of macrophages were associated with better outcome than very low or very high numbers. Our observations are reminiscent of the "hormesis hypothesis" and suggest that a relative lack of TAM may allow HL growth while macrophages display an inhibitory effect with increasing numbers. Above a certain threshold, TAM may again support tumor growth.

Evolution of sialic acids: Implications in xenotransplant biology

All living cells are covered with a dense “sugar-coat” of carbohydrate chains (glycans) conjugated to proteins and lipids. The cell surface glycome is determined by a non-template driven process related to the collection of enzymes that assemble glycans in a sequential manner. In mammals, many of these glycans are topped with sialic acids (Sia), a large family of acidic sugars. The “Sialome” is highly diverse owing to various Sia types, linkage to underlying glycans, range of carriers, and complex spatial organization. Presented at the front of cells, Sia play a major role in immunity and recognition of “self” versus “non-self,” largely mediated by the siglecs family of Sia-binding host receptors. Albeit many mammalian pathogens have evolved to hijack this recognition system to avoid host immune attack, presenting a fascinating host-pathogen evolutionary arms race. Similarly, cancer cells exploit Sia for their own survival and propagation. As part of this ongoing fitness, humans lost the ability to synthesize the Sia type N-glycolylneuraminic acid (Neu5Gc), in contrast to other mammals. While this loss had provided an advantage against certain pathogens, humans are continuously exposed to Neu5Gc through mammalian-derived diet (eg, red meat), consequently generating a complex immune response against it. Circulating anti-Neu5Gc antibodies together with Neu5Gc on some human tissues mediate chronic inflammation “xenosialitis” that exacerbate various human diseases (eg, cancer and atherosclerosis). Similarly, Neu5Gc-containing xenografts are exposed to human anti-Neu5Gc antibodies with implications to sustainability. This review aimed to provide a glimpse into the evolution of Sia and their implications to xenotransplantation.

Beyond cancer genes: colorectal cancer as robust intrinsic states formed by molecular interactions

Colorectal cancer (CRC) has complex pathological features that defy the linear-additive reasoning prevailing in current biomedicine studies. In pursuing a mechanistic understanding behind such complexity, we constructed a core molecular–cellular interaction network underlying CRC and investigated its nonlinear dynamical properties. The hypothesis and modelling method has been developed previously and tested in various cancer studies. The network dynamics reveal a landscape of several attractive basins corresponding to both normal intestinal phenotype and robust tumour subtypes, identified by their different molecular signatures. Comparison between the modelling results and gene expression profiles from patients collected at the second affiliated hospital of Zhejiang University is presented as validation. The numerical ‘driving’ experiment suggests that CRC pathogenesis may depend on pathways involved in gastrointestinal track development and molecules associated with mesenchymal lineage differentiation, such as Stat5, BMP, retinoic acid signalling pathways, Runx and Hox transcription families. We show that the multi-faceted response to immune stimulation and therapies, as well as different carcinogenesis and metastasis routes, can be straightforwardly understood and analysed under such a framework.

Hormesis in cancer immunology: Does the quantity of an immune reactant matter?

We recently reported that tumor-directed antibodies could either stimulate, or inhibit, tumor progression, dependent upon the dosage used. The narrow range over which this immune response curve (IRC) occurs is surprising. Here we discuss features of the IRC, the mechanisms identified so far, and the potential clinical implications.

Inverse hormesis of cancer growth mediated by narrow ranges of tumor-directed antibodies

Compelling evidence for naturally occurring immunosurveillance against malignancies informs and justifies some current approaches toward cancer immunotherapy. However, some types of immune reactions have also been shown to facilitate tumor progression. For example, our previous studies showed that although experimental tumor growth is enhanced by low levels of circulating antibodies directed against the nonhuman sialic acid N-glycolyl-neuraminic acid (Neu5Gc), which accumulates in human tumors, growth could be inhibited by anti-Neu5Gc antibodies from a different source, in a different model. However, it remains generally unclear whether the immune responses that mediate cancer immunosurveillance vs. those responsible for inflammatory facilitation are qualitatively and/or quantitatively distinct. Here, we address this question using multiple murine tumor growth models in which polyclonal antibodies against tumor antigens, such as Neu5Gc, can alter tumor progression. We found that although growth was stimulated at low antibody doses, it was inhibited by high doses, over a linear and remarkably narrow range, defining an immune response curve (IRC; i.e., inverse hormesis). Moreover, modulation of immune responses against the tumor by altering antibody avidity or by enhancing innate immunity shifted the IRC in the appropriate direction. Thus, the dualistic role of immunosurveillance vs. inflammation in modulating tumor progression can be quantitatively distinguished in multiple model systems, and can occur over a remarkably narrow range. Similar findings were made in a human tumor xenograft model using a narrow range of doses of a monoclonal antibody currently in clinical use. These findings may have implications for the etiology, prevention, and treatment of cancer.

Consideration of dual characters of exosomes in the tumour immune response

Efforts to get a strong and sustained anti-tumour immune response induced by a tumour specific antigen have failed, but sipuleucel-T has been approved by the US Food and Drug Administration (FDA). We noticed that exosomes secreted by tumour cells or immune cells may be crucially involved in the tumour immune response, whereas others have had inconsistent findings on exosome involvement. Based on immune network theory, we summarise research advances of exosomes and speculate that in the tumour immune response exosomes follow the immune response curve hypothesis. Exosomes activate simultabeously both immune activation and immune tolerance, but at different intensities. To obtain a desired anti-immune response, the initial point of immunity should be determined to achieve the strongest anti-tumour response, and repeated in vitro to extend and enhance this response. As a result, our hypothesis proposes that studies should now be directed at determining the exact time of exosome activity in maintaining a viable anti-tumour immune response in vivo.

Modeling the effects of a simple immune system and immunodeficiency on the dynamics of conjointly growing tumor and normal cells

In this paper, we develop a theoretical contribution towards the understanding of the complex behavior of conjoint tumor-normal cell growth under the influence of immuno-chemotheraputic agents under simple immune system response. In particular, we consider a core model for the interaction of tumor cells with the surrounding normal cells. We then add the effects of a simple immune system, and both immune-suppression factors and immuno-chemotherapeutic agents as well. Through a series of numerical simulations, we illustrate that the interdependency of tumor-normal cells, together with choice of drug and the nature of the immunodeficiency, leads to a variety of interesting patterns in the evolution of both the tumor and the normal cell populations.

Fractal immunology and immune patterning: potential tools for immune protection and optimization

Fractals are self-similar geometric patterns that are inherently embedded throughout nature. Their discovery and application have produced significant benefits across a wide variety of biomedical applications. Recently, complex physiological systems (e.g., neurological, respiratory, cardiovascular) have been shown to exhibit fractal dimensions that are capable of distinguishing among physiologic function versus dysfunction and, in turn, health versus disease. Additionally, fractal data suggest that the immune system operates under similar patterned relationships, and this is in keeping with the recent findings that immune-based diseases are organized according to specific patterns. This review considers the potential benefits of using fractal analysis along with considerations of nonlinearity, scaling, and chaos as calibration tools to obtain holistic information on immune-environment interactions. The potential uses of both synthetic and artificial immune systems for improved protection of the biological immune system are also discussed. The addition of holistic measures of immune status to currently collected biomarkers of immunotoxicity has the potential to increase the effectiveness of health risk assessment. The objective of extending fractal physiology analyses to the immune system would be to promote immune optimization as a public health benefit, which would include improved: (1) immunotoxicity testing and effective health risk reduction and (2) measures of effective immune management for children, adults, and aged individuals.

Cancer immunotherapy by immunosuppression

We have previously suggested that the stimulatory effect of a weak immune reaction on tumor growth may be necessary for the growth of incipient tumors. In the present paper, we enlarge upon and extend that idea by collecting evidence in the literature bearing upon this new hypothesis that a growing cancer, whether in man or mouse, is throughout its lifespan, probably growing and progressing because of continued immune stimulation by a weak immune reaction. We also suggest that prolonged immunosuppression might interfere with progression and thus be an aid to therapy. While most of the considerable evidence that supports the hypothesis comes from observations of experimental mouse tumors, there is suggestive evidence that human tumors may behave in much the same way, and as far as we can ascertain, there is no present evidence that necessarily refutes the hypothesis.

Immunologgical self-tolerance in allophenic and embryo-aggregated mice

Allophenic mice, supposedly containing almost equal numbers of cells derived from embryos of mouse strains C57Bl and FVB, were shown in a recent paper to grow the B16 melanoma, a long transplanted tumor of C57Bl origin, much better than did mice of either the parental C57Bl strain or the C57Bl × FVB F1 hybrid. Mice containing smaller proportions of C57Bl cells rejected the tumor. A reconsideration of these suprising data, in light of the current literature, suggests that the better growth of the tumor in the 50-50% allophenics than in the C57Bl parental strain was almost certainly caused by the tumor stimulation engendered by a weak anti-C57Bl immune reaction in the overtly healthy allophenic mice.