The TP53 tumor suppressor gene is considered to be one of the most important tumor suppressor genes in humans. Since its initial discovery more than 30 years ago, a tremendous amount of research has been conducted, with the aim to gain a better understanding of the gene itself, the function of the encoded protein p53 and of many associated pathways and proteins. A deeper insight into the role of p53 in cancer development is thought to be the key to find new targets for effective treatments against a huge variety of cancer. Somatic mutations in TP53 can be observed in about 50% of malignant human tumors, while germline TP53 mutations as not as common, but can lead to develop complex cancer syndromes such as Li-Fraumeni Syndrome. Individuals with inherent mutant TP53 are prone to develop various kinds of cancer, some at a very early age of onset. In the course of this project, eight novel mutations, found in a Swedish cohort of patients with germline TP53 mutations, were characterized to assess their intracellular localization as well as the effects on the regulation of apoptosis and cell cycle. It was shown, that some mutant p53 proteins are, despite severe genetic alterations, still capable of entering the nucleus and act as regulators for proteins vital in the fight against cellular stress and cancer development.