ABSTRACTThe bacterial pathogenPseudomonas syringaepv. tomato DC3000 must detoxify plant-produced hydrogen peroxide (H2O2) in order to survive in its host plant. Candidate enzymes for this detoxification include the monofunctional catalases KatB and KatE and the bifunctional catalase-peroxidase KatG of DC3000. This study shows that KatG is the major housekeeping catalase of DC3000 and provides protection against menadione-generated endogenous H2O2. In contrast, KatB rapidly and substantially accumulates in response to exogenous H2O2. Furthermore, KatB and KatG have nonredundant roles in detoxifying exogenous H2O2and are required for full virulence of DC3000 inArabidopsis thaliana. Therefore, the nonredundant ability of KatB and KatG to detoxify plant-produced H2O2is essential for the bacteria to survive in plants. Indeed, a DC3000 catalase triple mutant is severely compromised in its ability to growin planta, and its growth can be partially rescued by the expression ofkatB,katE, orkatG. Interestingly, our data demonstrate that although KatB and KatG are the major catalases involved in the virulence of DC3000, KatE can also provide some protectionin planta. Thus, our results indicate that these catalases are virulence factors for DC3000 and are collectively required for pathogenesis.

There have been several major problems that have plagued biopharmaceutical development since the end of the 1990s, but two in particular have reached the point where they are impacting the economic viability of the industry: the lack of efficacy of new drugs and increasing competition among therapeutics that broadly attack certain common diseases and disease areas. The US FDA has noted that the era of one-size-fits-all treatment may well be reaching its end days as companies increasingly adopt approaches that involve biomarkers (there are now commercial databases that purport to track over 11,000 of them). Pharmacogenomic biomarkers in particular are used to create diagnostics that help to differentiate or stratify the likely outcomes a patient will experience with a drug, which can now be said to be targeted or tailored to patients with particular traits (i.e., personalized), leading to an era of so-called precision medicine. As more is understood about diseases and the why and how of their effects on people through advances in biomarkers and genomics, personalized medicine is becoming a natural result of biomedical science and a natural trajectory for the innovation-based biopharmaceutical industry. The focus of this article is to examine an apparent divergence in that trajectory engendered by a growing differentiation in the approaches to personalized medicines in terms of their accompanying diagnostics: companion diagnostics are typically linked to a specific drug within its approved label, while complementary diagnostics are associated more broadly, usually not with a specific drug but with a class of drugs, and not confined to specific uses by labeling, with consequent ramifications for economic, regulatory and strategic considerations.

The retinoblastoma gene, RB1, is frequently inactivated in a subset of tumors, including retinoblastoma and osteosarcoma (OS). One characteristic of OS, as well as other tumors in which RB1 is frequently inactivated, is the lack of N-cadherin-mediated cellcell adhesions. The frequent inactivation of RB1 and parallel loss of N-cadherin expression in OS prompted us to ask whether these observations are directly related to each other. In this study, we observed reduced N-cadherin expression in RB1 ؊/؊ calvarial osteoblasts. In addition, RB1 ؊/؊ cell lines had increased migration potential compared to their RB1 ؉/؉ counterparts. These properties of RB1 ؊/؊ cell lines correlated with an adipogenic potential lacking in RB1 ؉/؉ cell lines, suggesting that each property is present in an immature progenitor cell. The isolation of a cell population with low surface expression of N-cadherin and enhanced adipogenic ability supports this view. Interestingly, the acute loss of pRb does not affect N-cadherin expression or migration or confer adipogenic potential to immortalized RB1 ؉/؉ calvarial cells, suggesting that these traits are not a direct consequence of pRb loss; rather, pRb loss leads to the expansion and immortalization of an immature progenitor pool characterized by these properties. The cell cycle regulatory pathway centered on the retinoblastoma protein, pRb, is inactivated in most human cancers. In the course of tumorigenesis, the components of this pathway are targeted in a tissue-specific manner. Examples include the loss of p16INK4A in melanoma, cyclin D1 overexpression in breast cancer, and the loss of pRb itself in osteosarcoma. Indeed, individuals who are heterozygous for the RB1 gene have a profoundly increased risk of developing osteosarcoma (OS) compared to the general population (19). In addition, the loss of pRb occurs in up to 60% of sporadic osteosarcomas (26). Osteosarcoma is the most common type of primary bone tumor in children and adults and is characterized by the production of aberrant bone matrix (24). The major cell type in osteosarcoma is osteoblastic (50 to 80%), with various amounts of chondroblastic and fibroblastic components (23). More than 80% of osteosarcomas are undifferentiated. OS samples frequently express alkaline phosphatase (ALP), an early marker of osteoblast differentiation, but lack osteocalcin, a mature osteoblast marker, suggesting that osteoblast differentiation is perturbed in OS (24).The tight correlation between RB1 loss and the development of OS suggests a tissue-specific function of pRb in bone that is important to its role as a tumor suppressor. Indeed, pRb promotes late stages of osteoblast differentiation through its interaction with the osteoblast-specific transcription factor RUNX2, resulting in enhanced RUNX2-dependent transcription (13,25). In RB1 Ϫ/Ϫ mice, calvarial osteoblasts lacking pRb express early markers of osteogenic differentiation, such as ALP, osteopontin, and RUNX2, whereas the expression of the late markers osteocalcin and osteoblast/osteocyte f...