The first in-depth analysis of the Human Protein Atlas project was released today that included a detailed display of systemic protein expression. In particular, this study highlighted proteins that have been linked to cancer, the number of circulating proteins within the bloodstream, and the targets for all currently marketed drugs.

The Human Protein Atlas is a multinational research project that contains an open-source database with millions of high-resolution images that show the spatial distribution of proteins from 44 diverse normal human tissues and 20 different cancer types, as well as 46 different human cell lines. November of 2014 saw the launch of the tissue-specific interactive map, which began to outline the distribution of human proteins in all primary tissues and organs of the body.

The investigators analyzed the approximately 20,000 protein coding regions within the human genome using a combination of genomics, transcriptomics, proteomics, and antibody-based profiling. The results of this comprehensive analysis, which builds on their previous work, is entitled “Tissue-based Atlas of the Human Proteome” and was published today in Science.  

Not surprisingly, the research team found that almost 50% of the proteins were ubiquitously expressed in all tissue types analyzed and that these “include known “housekeeping” genes encoding mitochondrial proteins and proteins involved in overall cell structure, translation, transcription, and replication,” the paper noted.   

Moreover, as validation for the specificity of their analysis the researchers found approximately 15% of the proteins were expressed in only one or several tissues or organs, including documented tissues-specific proteins, such as insulin and troponin. The tissues found with the highest level of protein enrichment were the testes, followed by the brain and the liver.

An interesting and unexpected discovery came when investigators analyzed the 618 proteins targeted by clinically approved drugs, of which 30% they found were expressed in all analyzed tissues.

“This is important information for the pharmaceutical industry,” said Mathias Uhlén, Ph.D., professor of microbiology at Stockholm's KTH Royal Institute of Technology and the director of the Human Protein Atlas program. “We show that 70% of the current targets for approved pharmaceutical drugs are either secreted or membrane-bound proteins. Interestingly, 30% of these protein targets are found in all analyzed tissues and organs. This could help explain some side effects of drugs and thus might have consequences for future drug development.”