Seventy percent of cancer patients have detectable metastases when they receive a diagnosis and 90% of cancer deaths result from metastases. These two facts emphasise the urgency for research to study the mechanisms and processes that enable metastasis. We need to develop a greater understanding of the cellular and molecular mechanisms that cause metastasis and also we need to do more. We must also consider the micro- and macro-environmental factors that influence this disease. Studying this environmental context has led us to update the ‘seed and soil’ hypothesis which dates back to the 19th century. This theory describes cancerous cells as seeds and the substrate as the soil in target organs though this may seem antiquated. Nonetheless, the tissue specificity that researchers have recently observed in metastatic colonisation supports the validity of the seed and soil theory. We now know that the metastatic potential of a tumour cell depends on multiple, reciprocal interactions between the primary tumour and distant sites. These interactions determine tumour progression. Studies of metastasis have allowed us to develop treatments that focus on therapeutic effectiveness. These new treatments account for the frequent metastasis of some tumours to target organs such as bones, lungs, brain, and liver. The purpose of this review is first to describe interactions between the cellular and molecular entities and the target organ tumour environment that enables metastasis. A second aim is to describe the complex mechanisms that mediate these interactions.

Colorectal cancer is a serious health problem, a challenge for research, and a model for studying the molecular mechanisms involved in its development. According to its incidence, this pathology manifests itself in three forms: family, hereditary, and most commonly sporadic, apparently not associated with any hereditary or familial factor. For the types having inheritance patterns and a family predisposition, the tumours develop through defined stages ranging from adenomatous lesions to the manifestation of a malignant tumour. It has been established that environmental and hereditary factors contribute to the development of colorectal cancer, as indicated by the accumulation of mutations in oncogenes, genes which suppress and repair DNA, signaling the existence of various pathways through which the appearance of tumours may occur. In the case of the suppressive and mutating tracks, these are characterised by genetic disorders related to the phenotypical changes of the morphological progression sequence in the adenoma/carcinoma. Moreover, alternate pathways through mutation in BRAF and KRAS genes are associated with the progression of polyps to cancer. This review surveys the research done at the cellular and molecular level aimed at finding specific alternative therapeutic targets for fighting colorectal cancer.

The two biological mechanisms that determine types of malignancy are infiltration and metastasis, for which tumour microenvironment plays a key role in developing and establishing the morphology, growth and invasiveness of a malignancy. The microenvironment is formed by complex tissue containing the extracellular matrix, tumour and non-tumour cells, a signalling network of cytokines, chemokines, growth factors, and proteases that control autocrine and paracrine communication among individual cells, facilitating tumour progression. During the development of the primary tumour, the tumour stroma and continuous genetic changes within the cells makes it possible for them to migrate, having to count on a pre-metastatic niche receptor that allows the tumour’s survival and distant growth. These niches are induced by factors produced by the primary tumour; if it is eradicated, the active niches become responsible for activating the latent disseminated cells. Due to the importance of these mechanisms, the strategies that develop tumour cells during tumour progression and the way in which the microenvironment influences the formation of metastasis are reviewed. It also suggests that the metastatic niche can be an ideal target for new treatments that make controlling metastasis possible.

The preparation of highly purified monolayer cultures of human cytotrophoblast cells essentially free of stromal and syncytial cells is described. Such cells subsequently form multinucleate syncytial cells in vitro. This is accompanied by the synthesis of heat-stable alkaline phosphatase and beta-HCG. A significant proportion of the multinucleate cells that form in monolayer cultures of early placentae arise as a result of an amitosis. It is suggested that this in vitro behavior may reflect an in vivo process.

El cuerpo humano está expuesto continuamente a microorganismos tanto fijos como transitorios, así como sus metabolitos tóxicos, lo cual puede conducir a la aparición y progresión del cáncer en sitios distantes al hábitat particular de cada microbio. Diversos estudios científicos han hecho posible entender la relación estrecha que existe entre microbioma y cáncer, ya que los componentes del primero, al tener la capacidad de migrar a diferentes zonas del cuerpo, pueden contribuir al desarrollo de diversas enfermedades crónicas. Los estudios de metagenómica sugieren que la disbiosis, en la microbiota comensal, está asociada con trastornos inflamatorios y varios tipos de cáncer, los cuales pueden ocurrir por sus efectos sobre el metabolismo, la proliferación celular y la inmunidad. La microbiota puede producir el cáncer cuando existen condiciones predisponentes, como en la etapa inicial de la progresión tumoral (iniciación), inestabilidad genética, susceptibilidad a la respuesta inmune del huésped, a la progresión y la respuesta a la terapia. La relación más estrecha, entre el microbioma y el cáncer, es a través de la desregulación del sistema inmune. En este trabajo revisamos las actuales evidencias sobre la asociación entre la microbiota y algunos tipos de cáncer como el cáncer gástrico, colorrectal, próstata, ovario, oral, pulmón y mama.