Hallmarks of cancer—Then and now, and beyond

Cancer presents a remarkably instructive perturbation of mechanisms manifesting in our biology that have gone awry, eliciting a malady that is inexorably increasing in incidence and societal burden concomitant with healthier aging. The wealth of knowledge and data forthcoming from decades of cancer research can be organized into conceptually distinct but interconnected parametric dimensions that define the mechanistic foundation of the disease: aberrantly acquired functional capabilities (the hallmarks of cancer), enabling phenotypic characteristics, hallmark-conveying cells populating cancer microenvironments, and systemic interactions. Collectively, they provide a logical framework with which to illuminate the operating systems of these outlaw organs, from inception through multistage tumorigenesis to adaptive evolution. This review presents a concise synthesis of the hallmark conceptualization as it has been refined during the past 25 years, including a corollary hypothesis that mechanism-guided hallmark co-targeting could offer impactful new therapeutic strategies for treating human cancers.