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Natural killer (NK) cells represent a heterogeneous subpopulation of lymphocytes of the innate immune system with a powerful antitumor activity, a function given by a complex collection of receptors. They act synergistically to recognize, regulate, or amplify the response according to the microenvironment, thus highlighting Toll-like receptors (TLRs), a type of receptors that allows sensing evolutionarily molecules conserved of pathogens known as pathogen-associated molecular patterns (PAMPs) and/or damage-associated molecular patterns (DAMPs). Those TLRs are essential to start the immune response. There is little information about the different subpopulations that form NK cells as well as their expression profile of innate immune response receptors in hematological cancers.

Gastric cancer is one of the types of cancer that is associated with Helicobacter pylori infection. The infection starts in childhood, and 50–90% of the population in the world is infected. The clinical symptoms can be stomach pain, gastritis, atrophy gastric, and only 2–3% of the infected population developed gastric cancer. The majority of gastric cancers are adenocarcinomas. From Lauren’s histological classification, gastric cancer is divided into two large groups: intestinal and diffuse. The cells that gives rise to them are different and the epidemiologic features and diagnosis are different according to gender and age; however; the survival rate is approximately of 5-years. Surgery is the only radical treatment, but the adjuvant treatment is chemotherapy and radiotherapy which unfortunately lead to only a modest survival benefit. On this review, we describe the major risk factors associated with the bacteria: cagPAI, CagA, VacA, HOPs, as well as host immune and inflammatory responses: immune cells, Toll-like receptors, cytokines, immune signal pathway, genetic predisposition, such as single nucleotide polymorphisms (SNP’s) and environmental factors: age, high salt intake, diets low in fruit and vegetables, alcohol intake, and tobacco use. Finally, we included the interaction of all factors for the development of gastric cancer. Knowing and understanding the role of all factors in the development of gastric cancer will allow the implementation of better therapies and improve patient prognosis.