Gastric Cancer and Viruses: A Fine Line between Friend or Foe

Gastric cancer (GC) is a significant health concern worldwide, with a GLOBOCAN estimate of 1.08 million novel cases in 2020. It is the leading cause of disability-adjusted life years lost to cancer, with the fourth most common cancer in males and the fifth most common cancer in females. Strategies are pursued across the globe to prevent gastric cancer progression as a significant fraction of gastric cancers have been linked to various pathogenic (bacterial and viral) infections. Early diagnosis (in Asian countries), and non-invasive and surgical treatments have helped manage this disease with 5-year survival for stage IA and IB tumors ranging between 60% and 80%. However, the most prevalent aggressive stage III gastric tumors undergoing surgery have a lower 5-year survival rate between 18% and 50%. These figures point to a need for more efficient diagnostic and treatment strategies, for which the oncolytic viruses (OVs) appear to have some promise. OVs form a new therapeutic agent class that induces anti-tumor immune responses by selectively killing tumor cells and inducing systemic anti-tumor immunity. On the contrary, several oncogenic viruses have been shown to play significant roles in malignancy progression in the case of gastric cancer. Therefore, this review evaluates the current state of research and advances in understanding the dual role of viruses in gastric cancer.

Cancer risk across mammals

Cancer is a ubiquitous disease of metazoans, predicted to disproportionately affect larger, long-lived organisms owing to their greater number of cell divisions, and thus increased probability of somatic mutations1,2. While elevated cancer risk with larger body size and/or longevity has been documented within species3-5, Peto's paradox indicates the apparent lack of such an association among taxa6. Yet, unequivocal empirical evidence for Peto's paradox is lacking, stemming from the difficulty of estimating cancer risk in non-model species. Here we build and analyse a database on cancer-related mortality using data on adult zoo mammals (110,148 individuals, 191 species) and map age-controlled cancer mortality to the mammalian tree of life. We demonstrate the universality and high frequency of oncogenic phenomena in mammals and reveal substantial differences in cancer mortality across major mammalian orders. We show that the phylogenetic distribution of cancer mortality is associated with diet, with carnivorous mammals (especially mammal-consuming ones) facing the highest cancer-related mortality. Moreover, we provide unequivocal evidence for the body size and longevity components of Peto's paradox by showing that cancer mortality risk is largely independent of both body mass and adult life expectancy across species. These results highlight the key role of life-history evolution in shaping cancer resistance and provide major advancements in the quest for natural anticancer defences.

Cell functioning in norm and pathology in terms of the activity paradigm: Oncogenesis

Over the past years many theories of carcinogenesis have been developed. Nowadays, there are two prevalent theories of carcinogenesis - two-hit hypothesis, which considers mutations as the main factor in malignization and tissue hypothesis, which considers tissue homeostasis disruption for providing cells transformation. Both of these theories explain cancer origin basing on principles of the reactivity paradigm. This paradigm emphasizes role of different stimuli in malignization. However, this approach does not provide us with sufficient support in progress towards either understanding of cancer origin or effective treatment strategies. In contrast to the reactivity paradigm, we intend to explain oncogenesis within the activity paradigm. Upon this approach, cells' activity is goal-directed and is determined by a future event - the adaptive result. The adaptive result is a proper interaction between the cell and its environment, which provides the cell with required metabolites. To achieve this result cells have to cooperate with each other and synchronize their needs. If cells fail to satisfy their metabolic 'needs' they have to reorganize their activity. This results in morpho-functional restructuring of cells. Summing up, we consider carcinogenesis to be a part of goal-directed adaptive activity of cells. Morphological and genetic atypia of cancer cells is a variant reorganization of cells' activity. Consequently, for better treatment, we should bring both transforming cells and their microenvironment to a novel cooperation and reorganization of their activity.

The Double-Edged Sword Role of Viruses in Gastric Cancer

Due to its high morbidity and mortality, gastric cancer is a topic of a great concern throughout the world. Major ways of treatment are gastrectomy and chemotherapy, unfortunately they are not always successful. In a search for more efficient therapy strategies, viruses and their potential seem to be an important issue. On one hand, several oncogenic viruses have been noticed in the case of gastric cancer, making the positive treatment even more advantageous, but on the other, viruses exist with a potential therapeutic role in this malignancy.