Cancer can be defined as genome disease. Cancer cells arise as a consequence of genetic alterations that accumulate and confer a growing advantage over the normal tissue cell counterparts. Each tumor type or subtype, and probably in each patient, can be characterized by a specific mutation or group of mutations affecting specific genes in specific combinations. In addition, cancer cells, and in particular those from solid tumors, are also characterized by massive (and restricted) genome rearrangements, gains, deletions, etc. As a consequence of all these genome alterations tumor cells display a completely new program of gene expression that differentiates from normal tissue cells. Moreover, as tumors progress into more malignant and aggressive forms, these genome alterations and consequently the gene expression program also vary. Importantly, these changes in genome architecture, mutations and gene expression also provide important clues about potential targets that once inhibited can kill selectively those cells bearing these alterations, i.e.: possible therapeutic targets. Furthermore, these specific alterations can also help identifying patients or group of patients that, as a consequence of these alterations, may also display differential diagnose or prognostic. In other words, it is possible to stratify and recognize patients in a specific tumor type that would require a more appropriate and aggressive therapeutic option.

Finally, comparative genomics or metagenomics can be also used to identify potential similarities or differences between human cases and tumors originated in distinct model systems, thus deserving as a prerequisite for the validation of these models as preclinical platforms for drug testing.

The activities of the Molecular Oncology Unit in the genomic area are centered in identifying these genomic alterations in human cancer samples and in the different genetically engineered mouse models generated. We are currently analyzing different mutations and copy gains/deletions, in a targeted or massive manner, and we are also analyzing the different programs of gene expression, including miRNAs and lncRNAs. The different technologies include different types of microarray analyses and different qPCR approaches. The integration of the Molecular Oncology Unit at the Institute of Biomedical Research of the University Hospital "12 de Octubre"  also allows the use of Next Generation Sequence (NGS) platforms.

Tissue stem cells are in charge of the turnover of aged or damaged cells ensuring tissue and organ function throughout a lifetime. Cancer stem cells are responsible for primary tumour growth and dissemination to other parts of the body to form secondary tumours (metastasis). The similarities between these two types of stem cells hinder the development of targeted antitumour therapies. In the Molecular Oncology Unit at Ciemat we work to elucidate the role of stem cells in tumour development and in the evaluation of new specific anti-tumour therapies aimed at cancer stem cells that do not affect other cell populations. Specificity would increase the efficacy of treatments and reduce adverse side effects.

We identify stem cell populations in tumour development transgenic animal models from our laboratory, based on the expression of specific stem cell markers (CD34, CD44, CD133, ALDH, Side population¿) that also allow their isolation. Once they have been identified and isolated we can explore how different genetic alterations affect stem cell behaviour and their impact on tissue homeostasis and tumour development. For this purpose we carry out proliferation studies, functional genomics analyses, in vitro clonogenicity and in vivo regenerative potential assays, and tumorigenicity assays. Another approach consists of the use of xenograft models of human tumour derived cells in immune deficient mice to characterise cancer stem cell populations and their response to the anti-tumour therapies under evaluation in our laboratory on these cell populations.

 

Transgenic animals are a tool used in almost all lines of work from our laboratory. Despite the apparent genetic differences in size and metabolism between humans and mice, murine models have been and are of great importance for the study of various types of cancer, constituting in many cases the best model system to study the etiology and treatment of these diseases. In many cases, specific molecular lesions cause similar diseases in both species.

In our projects , we use both animals overexpressing (transgenic mice by standard addition) and animals with reduced or suppressed expression of proteins of interest (knock-down and knock- out mice). And we use both animals in which these changes affect to all the cells in the body, or only part of them (tissue -specific) , and either constitutively or inducibly, so that we can control in time and space the gene modification to perform.

 

Transposons are mobile genetic elements ,which have the ability to "jump" from one place to another in the genome. The development of mutagenic transposons as as a method of insertional mutagenesis in model systems has been an important contribution to the study of cancer, since it allows the identification of genes whose mutation leads to the development of tumor lesions . An artificial transposon system, Sleeping Beauty (SB), which is active in mammalian cells, has been recently generated. When an SB transposon designed for altering the expression of both oncogenes and tumor suppressors is specifically activated in target tissues of experimental mice, sometimes it leads to the appearance of tumor lesions. Once tumors are generated, it is possible to determine the transposon insertion sites in the genome by massive sequencing techniques. Comparison of integration sites in multiple tumors allows the identification of genomic locations where the transposon is integrated to a greater extent than expected by chance , which almost always correspond to oncogenes or tumor suppressor genes, some known and others not. This technology has been successfully used for the determination of "driver" genes in several tumor types , and we're using it for the study of cancer in skin and other epithelial tissues.