*Helicobacter pylori*; a Way to Gastric Cancer?

*Norma Sánchez-Zauco, Erandi Pérez-Figueroa and Carmen Maldonado-Bernal*

## **Abstract**

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.

**Keywords:** *Helicobacter pylori*, inflammatory response, dysplasia, metaplasia, gastric cancer

## **1. Introduction**

*Helicobacter pylori* is a Gram-negative bacterial pathogen that infects more than half of the human population worldwide. It is usually acquired during childhood and it is able to establish a lifelong chronic infection [1]. *H. pylori* is characterized by an exceptionally high genetic diversity and variability. Some pathogenic mechanisms include relatively inefficient DNA repair mechanisms as well as natural competence for transformation and the ability to integrate small fragments of homologous DNA into the chromosome. The species of Helicobacter are divided into large phylogeographic populations with distinct geographical distributions. In 22 countries in Central and South America and Asia, a prevalence of approximately 70% or higher around age 60 years was reported in the late 1990s and early 2000s, with a decreasing tendency in different time periods in most countries where data were available [1]. This text is a historical review of the data which exist on host-helicobacter interaction.
