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T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive immature T-cell cancer. Hotspot mutations in JAK-STAT pathway membersIL7R,JAK1andJAK3were analyzed in depth. However, the role ofSTAT5AorSTAT5Bmutations promoting their hyperactivation is poorly understood in the context of T-cell cancer initiation and acute leukemia progression. Importantly, the driver mutationSTAT5BN642Hencodes the most frequent activating STAT5 variant in T-ALL associated with poor prognosis. Here, we show that hyperactive STAT5 promotes early T-cell progenitor (ETP)-ALL-like cancer in mice and upregulated genes involved in T-cell receptor signaling (TCR), even in absence of surface TCR promoting. Importantly, these genes were also overexpressed in human T-ALL and other STAT5-dependent T-cell cancers. Moreover, human T-ALL cells were sensitive to pharmacologic inhibition by dual STAT3/5 degraders or ZAP70 tyrosine kinase blockers. Thus, we define STAT5 target genes in T-ALL that promote pre-TCR signaling mimicry. We propose therapeutic targeting using selective ZAP70 or STAT3/5 inhibitors in a subgroup of T-ALL patients with prominent IL-7R-JAK1/3-STAT5 activity.SignificanceWe provide detailed functional characterizations of hyperactive STAT5A or STAT5B in thymic T-cell development and transformation. We found that hyperactive STAT5 transcribes T-cell-specific kinases or pre-TCR signaling hubs to promote T-ALL. Biomolecular and next-generation-sequencing methods, transgenesis and pharmacologic interference revealed that hyperactive STAT5 is a key oncogenic driver that can be targeted in T-ALL using STAT3/5 or SYK family member tyrosine kinase inhibitors.Conflict of interestThe authors declare no potential conflicts of interest.

Oncology is one of the most important fields of personalized medicine as a majority of efforts in this field have recently centered on targeted cancer drug development. New tools are continuously being developed that promise to make cancer treatment more efficacious while causing fewer side effects. Like most industries, the biopharmaceutical industry is also following certain global trends and these are analyzed in this article. As academia and industry are mutually dependent on each other, researchers in the field should be aware of those trends and the immediate consequences for their research. It is important for the future of this field that there is a healthy relationship among all interested parties as the challenges of personalized medicine are becoming ever more complex.

Design principles and syntheses of three haptens that were recently reported to generate amide bond cleaving catalytic antibodies are described. The hapten designs sought to induce acidic and/or basic residues in antibody binding sites via charge complementarity, and also to generate a hydrophobic binding pocket for an external phenol nucleophile. The charged yet aromatic nature of these haptens presented some unique synthetic challenges and solutions to which are described below.

A zwitterionic hapten 4 featuring both positively and negatively charged functional groups was designed and synthesized with the goal of generating catalytic antibodies for the hydrolysis of ester 6 and amide 7. Of the 36 monoclonal antibodies specific to BSA-4 (bovine serum albumin) that were isolated, six accelerated the hydrolysis of 6. Two catalytic antibodies with distinctively different and representative kinetic behaviors were selected for detailed kinetic studies. Whereas H8-2-6F11 showed burst kinetic behavior, which can be attributed to the formation of an acyl intermediate, H8-1-2D5 did not, but it did exhibit high multiple turnover activity. The rate of hydrolysis of 6 catalyzed by H8-1-2D5 followed Michaelis-Menten kinetics; the apparent values of the Michaelis-Menten constant Km and the catalytic constant kcat were 488 microM and 3.5 min(-1), respectively. The catalytic rate enhancement (kcat/kun) observed for H8-1-2D5 was 1.3 x 10(5), which is approximately two orders of magnitude greater than those for monofunctional haptens. Thus H8-1-2D5 compares well in catalytic activity with antibodies isolated by a related approach called heterologous immunization.

Purpose: Cathepsin S (Cat-S) is a lysosomal cysteine protease found overexpressed in many cancers, and it has been associated with tumor aggressiveness. In this sense, increasing evidence indicates that Cat-S is secreted into the tumor environment causing extracellular matrix component degradation, thereby facilitating invasion, angiogenesis and metastasis during tumor progression. The aim of this work was to evaluate the anti-cancer activity of an antagonistic anti-Cat-S monoclonal antibody, Fsn0503h, in several cell lines in vitro and in the Colo-205 colon carcinoma xenograft. Experimental Procedures: Fsn0503h was provided by Fusion Antibodies Ltd. [Clin Cancer Res 2009;15(19):6042-51]. Cat-S protein expression was studied in a panel of breast, head and neck, hepatocarcinoma, ovarian, pancreas, cholangiocarcinoma, prostate, glioma, renal, and colon cancer cell lines by Western blot. Fsn0503h anti-invasive effects were evaluated in vitro by Matrigel invasion assay in Cat-S-expressing cells. Anti-proliferative effects of Fsn0503h were determined by the MTT assay. Furthermore, subcellular localization of Cat-S was assessed by immunofluorescence. In vivo, Fsn0503h anti-tumor efficacy was evaluated in in nude mice bearing palpable Colo205 tumor xenografts, in different doses and dosing schedules. Results: Cat-S was found to be expressed in 11 out of 36 cancer cell lines, including renal cancer cells lines Caki-1 and Caki-2. Interestingly, Cat-S expression had not been previously reported in renal cancer cell lines. Furthermore, it was observed for the first time that TNF-γ can induce the expression of Cat-S in the renal cancer cell line 786-0. In vitro, Fsn0503h displayed anti-proliferative effects in some Cat-S-expressing cell lines. In addition, exposure to Fsn0503h (125 nM) for 24 h induced a significant reduction in the invasive capacity of all cell lines expressing Cat-S. Similar results were obtained with another Cat-S inhibitor, Z-FL-COCHO. Subsequent evaluation of the subcellular localization of Cat-S in 786-0 and CAKI-1 cells showed that the protein is mainly expressed in the cytoplasm. Finally, in vivo experiments showed that in this study, 10 mg/kg Fsn0503h administered intravenously in a thrice a week regimen was the most active dose schedule in a Colo205 xenograft model. Conclusions: Our results indicate that Cat-S is a suitable therapeutic target in some solid tumors. In this regard, Fsn0503h, the first humanized monoclonal antibody against Cat-S, not only inhibits the invasiveness of cancer cell lines in vitro but also displays in vivo anti-tumor effects. These results validate Cat-S as a therapeutic target and encourage further development of the Fsn0503h antibody. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C161. Citation Format: Ramiro Vázquez, Lucil Astorgues-Xerri, Esteban Cvitkovic, Mohamed Bekradda, Roman Fleck, Julie Gormley, Richard Buick, Paul Kerr, Eric Raymond, Maurizio D'Incalci, Roberta Frapolli, María Eugenia Riveiro. Fsn0503h antibody-mediated blockade of cathepsin S as potential therapeutic strategy for the treatment of solid tumors. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C161.