Stromal Fibroblast in Age-Related Cancer: Role in Tumorigenesis and Potential as Novel Therapeutic Target.

Incidence of most common cancers increases with age due to accumulation of damage to cells and tissues. Stroma, the structure close to the basement membrane, is gaining increased attention from clinicians and researchers due to its increasingly, yet incompletely understood role in the development of age-related cancer. With advanced age, stroma generates a pro-tumorigenic microenvironment, exemplified by the senescence-associated secretory phenotype (SASP). Components of the SASP, such as cytokines, chemokines, and high energy metabolites are main drivers of age-related cancer initiation and sustain its progression. Our purpose is to provide insight into the mechanistic role of the stroma, with particular emphasis on stromal fibroblasts, on the development of age-related tumors. We also present evidence of the potential of the stroma as target for tumor therapy. Likewise, a rationale for age-related antitumor therapy targeting the stroma is presented. We expect to foster debate on the underlining basis of age-related cancer pathobiology. We also would like to promote discussion on novel stroma-based anticancer therapeutic strategies tailored to treat the elderly.

Functional Characterization of a WWP1/Tiul1 Tumor-derived Mutant Reveals a Paradigm of Its Constitutive Activation in Human Cancer.

Although E3 ubiquitin ligases are deemed to play key roles in normal cell function and homeostasis, whether their alterations contribute to cancer pathogenesis remains unclear. In this study, we sought to investigate potential mechanisms that govern WWP1/Tiul1 (WWP1) ubiquitin ligase activity, focusing on its ability to trigger degradation of TGFß type I receptor (TßRI) in conjunction with Smad7. Our data reveal that the WWP1 protein is very stable at steady states because its autopolyubiquitination activity is silenced due to an intra-interaction between the C2 and/or WW and Hect domains that favors WWP1 monoubiquitination at the expense of its polyubiquitination or polyubiquitination of TßRI. Upon binding of WWP1 to Smad7, this functional interplay is disabled, switching its monoubiquitination activity toward a polyubiquitination activity, thereby driving its own degradation and that of TßRI as well. Intriguingly, a WWP1 point mutation found in human prostate cancer disrupts this regulatory mechanism by relieving the inhibitory effects of C2 and WW on Hect and thereby causing WWP1 hyperactivation. That cancer-driven alteration of WWP1 culminates in excessive TßRI degradation and attenuated TGFß cytostatic signaling, a consequence that could conceivably confer tumorigenic properties to WWP1.