Suicide journey of H. pylori through gastric carcinogenesis: the role of non-H. pylori microbiome and potential consequences for clinical practice.

Despite being one of the most studied cancer-related infections, the relationship between Helicobacter pylori infection and gastric adenocarcinoma (GC) remains, in some points, obscure. Based on a critical analysis of the available literature regarding stomach microbiota, we aimed to shed light to a possible new interpretation of the current understanding about the Helicobacter pylori-related GC carcinogenesis. We analyzed data from the literature on Helicobacter pylori and other potential carcinogenic pathogens, in both benignant conditions and gastric adenocarcinoma. Helicobacter pylori is the dominant microorganism in benignant conditions as non-complicated gastritis. In atrophic gastritis, metaplasia and, mainly, in gastric adenocarcinoma, a strong reduction in Helicobacter pylori abundance, and increased occurrence of other microorganisms is strongly demonstrated by metagenomic experiments. While causing peptic disease and keeping the stomach's high acidity, Helicobacter pylori infection avoids gastric infection by carcinogenic intestinal microbiota. Nevertheless, Helicobacter pylori persistence may also provoke an atrophic gastritis, a condition that causes its own decline, due to a microenvironment modification, including reduced acidity, resulting in Helicobacter pylori substitution by a cancer-prone microbiota. This new interpretation might result in a dramatic modification on clinical management of Helicobacter pylori-related gastric disease.

Traps and trumps from adjacent-to-tumor samples in gastric cancer research.

The search for cancer biomarkers is frequently based on comparisons between tumors and adjacent-to-tumor samples. However, even after histological confirmation of been free of cancer cells, these adjacent-to-tumor samples might harbor molecular alterations which are not sufficient to cause them to look like cancer, but can differentiate these cells from normal cells. When comparing them, potential biomarkers are missed, and mainly the opportunity of finding initial aberrations presents in both tumors and adjacent samples, but not in true normal samples from non-cancer patients, resulting in misinterpretations about the carcinogenic process. Nevertheless, collecting adjacent-to-tumor samples brings trumps to be explored. The addition of samples from non-cancer patients opens an opportunity to increase the finds of the molecular cascade of events in the carcinogenic process. Differences between normal samples and adjacent samples might represent the first steps of the carcinogenic process. Adding samples of non-cancer patients to the analysis of molecular alterations relevant to the carcinogenic process opens a new window of opportunities to the discovery of cancer biomarkers and molecular targets.

The role of piRNA and its potential clinical implications in cancer.

Epigenetic mechanisms work in an orchestrated fashion to control gene expression in both homeostasis and diseases. Among small noncoding RNAs, piRNAs seem to meet the necessary requirements to be included in this epigenetic network due to their role in both transcriptional and post-transcriptional regulation. piRNAs and PIWI proteins might play important roles in cancer occurrence, prognosis and treatment as reported previously. Nevertheless, the potential clinical relevance of these molecules has yet been elucidated. A brief overview of piRNA biogenesis and their potential roles as part of an epigenetic network that is possibly involved in cancer is provided. Moreover, potential strategies based on the use of piRNAs and PIWI proteins as diagnostic and prognostic biomarkers as well as for cancer therapeutics are discussed.