General theories are reductionist explications of apparently independent facts. Here, in reviewing the literature, I develop a GT to simplify the cluttered landscape of cancer therapy targets by revealing they cluster parsimoniously according to only a few underlying principles. The first principle is that targets can be only exploited by either or both of two fundamentally different approaches: causality-inhibition, and ‘acausal’ recognition of some marker or signature. Nonetheless, each approach must achieve both of two separate goals, efficacy and selectivity ; (...) if the mechanisms are known, this provides a definition of rational treatment. The second principle is target fragmentation, whereby the target may perform up to three categoric functions, potentially mediated by physically different target molecules, even on different cell types, or circulating freely. This GT remains incomplete until the minimal requirements for cure, or alternatively, proof that cure is impossible, become predictable. A reductionist General Theory of Cancer Targets is presented, proposing that all good targets are based either on causality-inhibition, or recognition; essential tasks emerge differently in each case. Sophisticated hybrids may provide additional benefit. General theory analysis, including target fragmentation concepts, provides deeper insights into therapeutic mechanisms. (shrink)

Cancer is an evolutionary and ecological process in which complex interactions between tumour cells and their environment share many similarities with organismal evolution. Tumour cells with highest adaptive potential have a selective advantage over less fit cells. Naturally occurring transmissible cancers provide an ideal model system for investigating the evolutionary arms race between cancer cells and their surrounding micro‐environment and macro‐environment. However, the evolutionary landscapes in which contagious cancers reside have not been subjected to comprehensive investigation. Here, we provide a (...) multifocal analysis of transmissible tumour progression and discuss the selection forces that shape it. We demonstrate that transmissible cancers adapt to both their micro‐environment and macro‐environment, and evolutionary theories applied to organisms are also relevant to these unique diseases. The three naturally occurring transmissible cancers, canine transmissible venereal tumour (CTVT) and Tasmanian devil facial tumour disease (DFTD) and the recently discovered clam leukaemia, exhibit different evolutionary phases: (i) CTVT, the oldest naturally occurring cell line is remarkably stable; (ii) DFTD exhibits the signs of stepwise cancer evolution; and (iii) clam leukaemia shows genetic instability. While all three contagious cancers carry the signature of ongoing and fairly recent adaptations to selective forces, CTVT appears to have reached an evolutionary stalemate with its host, while DFTD and the clam leukaemia appear to be still at a more dynamic phase of their evolution. Parallel investigation of contagious cancer genomes and transcriptomes and of their micro‐environment and macro‐environment could shed light on the selective forces shaping tumour development at different time points: during the progressive phase and at the endpoint. A greater understanding of transmissible cancers from an evolutionary ecology perspective will provide novel avenues for the prevention and treatment of both contagious and non‐communicable cancers. (shrink)

Similar to parasites, cancer cells depend on their hosts for sustenance, proliferation and reproduction, exploiting the hosts for energy and resources, and thereby impairing their health and fitness. Because of this lifestyle similarity, it is predicted that cancer cells could, like numerous parasitic organisms, evolve the capacity to manipulate the phenotype of their hosts to increase their own fitness. We claim that the extent of this phenomenon and its therapeutic implications are, however, underappreciated. Here, we review and discuss what can (...) be regarded as cases of host manipulation in the context of cancer development and progression. We elaborate on how acknowledging the applicability of these principles can offer novel therapeutic and preventive strategies. The manipulation of host phenotype by cancer cells is one more reason to adopt a Darwinian approach in cancer research. -/- . (shrink)

From an evolutionary perspective, both atavism and somatic evolution/convergent evolution theories can account for the consistent occurrence, and astounding attributes of cancers: being able to evolve from a single cell to a complex organized system, and malignant transformations showing significant similarities across organs, individuals, and species. Here, we first provide an overview of these two hypotheses, including the possibility of them not being mutually exclusive, but rather potentially representing the two extremes of a continuum in which the diversity of cancers (...) can emerge. In reviewing the current literature, we also discuss the criteria that should be applied to discriminate between the two competing theories and to determine their relevant contributions to oncogenesis and cancer progression. Finally, we deliberate on the potential applications of this conceptual framework in developing novel treatment strategies. (shrink)

Genomic instability is a hallmark of cancer. Cancer cells that exhibit abnormal chromosomes are characteristic of most advanced tumours, despite the potential threat represented by accumulated genetic damage. Carcinogenesis involves a loss of key components of the genetic and signalling molecular networks; hence some authors have suggested that this is part of a trend of cancer cells to behave as simple, minimal replicators. In this study, we explore this conjecture and suggest that, in the case of cancer, genomic instability has (...) an upper limit that is associated with a minimal cancer cell network. Such a network would include (for a given microenvironment) the basic molecular components that allow cells to replicate and respond to selective pressures. However, it would also exhibit internal fragilities that could be exploited by appropriate therapies targeting the DNA repair machinery. The implications of this hypothesis are discussed. (shrink)

In the atavistic model of cancer progression, tumor cell dedifferentiation is interpreted as a reversion to phylogenetically earlier capabilities. The more recently evolved capabilities are compromised first during cancer progression. This suggests a therapeutic strategy for targeting cancer: design challenges to cancer that can only be met by the recently evolved capabilities no longer functional in cancer cells. We describe several examples of this target‐the‐weakness strategy. Our most detailed example involves the immune system. The absence of adaptive immunity in immunosuppressed (...) tumor environments is an irreversible weakness of cancer that can be exploited by creating a challenge that only the presence of adaptive immunity can meet. This leaves tumor cells more vulnerable than healthy tissue to pathogenic attack. Such a target‐the‐weakness therapeutic strategy has broad applications, and contrasts with current therapies that target the main strength of cancer: cell proliferation. (shrink)

Despite the remarkable achievements of novel targeted anti‐cancer drugs, most therapies only produce remission for a limited time, resistance to treatment, and relapse, often being the ultimate outcome. Drug resistance is due to highly efficient adaptive strategies utilized by cancer cells. Exogenous and endogenous stress stimuli are known to induce first‐line responses, capable of re‐establishing cellular homeostasis and determining cell fate decisions. Cancer cells may also mount second‐line adaptive strategies, such as the mutator response. Hypermutable subpopulations of cells may expand (...) under severe selective stress, thereby accelerating the emergence of adapted clones. As with first‐line protective responses, these strategies appear highly conserved, and are found in yeasts and bacteria. We hypothesize that evolutionarily conserved programs rheostatically regulate mutability in fluctuating environments, and contribute to drug resistance in cancer cells. Elucidating the conserved genetic and molecular mechanisms may present novel opportunities to increase the effectiveness of cancer therapies. (shrink)

Various threshold Boolean networks, a formalism used to model different types of biological networks, can produce similar dynamics, i.e. share same behaviors. Among them, some are complex, others not. By computing both structural and behavioral complexities, we show that most TBNs are structurally complex, even those having simple behaviors. For this purpose, we developed a new method to compute the structural complexity of a TBN based on estimates of the sizes of equivalence classes of the threshold Boolean functions composing the (...) TBN. (shrink)