Therapeutic targeting of SLC6A8 creatine transporter suppresses colon cancer progression and modulates human creatine levels.

Colorectal cancer (CRC) is a leading cause of cancer mortality. Creatine metabolism was previously shown to critically regulate colon cancer progression. We report that RGX-202, an oral small-molecule SLC6A8 transporter inhibitor, robustly inhibits creatine import in vitro and in vivo, reduces intracellular phosphocreatine and ATP levels, and induces tumor apoptosis. RGX-202 suppressed CRC growth across KRAS wild-type and KRAS mutant xenograft, syngeneic, and patient-derived xenograft (PDX) tumors. Antitumor efficacy correlated with tumoral expression of creatine kinase B. Combining RGX-202 with 5-fluorouracil or the DHODH inhibitor leflunomide caused regressions of multiple colorectal xenograft and PDX tumors of distinct mutational backgrounds. RGX-202 also perturbed creatine metabolism in patients with metastatic CRC in a phase 1 trial, mirroring pharmacodynamic effects on creatine metabolism observed in mice. This is, to our knowledge, the first demonstration of preclinical and human pharmacodynamic activity for creatine metabolism targeting in oncology, thus revealing a critical therapeutic target.

Benchmarks in clinical productivity: a national comprehensive cancer network survey.

PURPOSE: Oncologists in academic cancer centers usually generate professional fees that are insufficient to cover salaries and other expenses, despite significant clinical activity; therefore, supplemental funding is frequently required in order to support competitive levels of physician compensation. Relative value units (RVUs) allow comparisons of productivity across institutions and practice locations and provide a reasonable point of reference on which funding decisions can be based. METHODS: We reviewed the clinical productivity and other characteristics of oncology physicians practicing in 13 major academic cancer institutions with membership or shared membership in the National Comprehensive Cancer Network (NCCN). The objectives of this study were to develop tools that would lead to better-informed decision making regarding practice management and physician deployment in comprehensive cancer centers and to determine benchmarks of productivity using RVUs accrued by physicians at each institution. Three hundred fifty-three individual physician practices across the 13 NCCN institutions in the survey provided data describing adult hematology/medical oncology and bone marrow/stem-cell transplantation programs. Data from the member institutions participating in the survey included all American Medical Association Current Procedural Terminology (CPT®) codes generated (billed) by each physician during each organization's fiscal year 2003 as a measure of actual clinical productivity. Physician characteristic data included specialty, clinical full-time equivalent (CFTE) status, faculty rank, faculty track, number of years of experience, and total salary by funding source. The average adult hematologist/medical oncologist in our sample would produce 3,745 RVUs if he/she worked full-time as a clinician (100% CFTE), compared with 4,506 RVUs for a 100% CFTE transplant oncologist. RESULTS AND CONCLUSION: Our results suggest specific clinical productivity targets for academic oncologists and provide a methodology for analyzing potential factors associated with clinical productivity and developing clinical productivity targets specific for physicians with a mix of research, administrative, teaching, and clinical salary support.

Identification of biomarkers for tumor endothelial cell proliferation through gene expression profiling.

Extensive efforts are under way to identify antiangiogenic therapies for the treatment of human cancers. Many proposed therapeutics target vascular endothelial growth factor (VEGF) or the kinase insert domain receptor (KDR/VEGF receptor-2/FLK-1), the mitogenic VEGF receptor tyrosine kinase expressed by endothelial cells. Inhibition of KDR catalytic activity blocks tumor neoangiogenesis, reduces vascular permeability, and, in animal models, inhibits tumor growth and metastasis. Using a gene expression profiling strategy in rat tumor models, we identified a set of six genes that are selectively overexpressed in tumor endothelial cells relative to tumor cells and whose pattern of expression correlates with the rate of tumor endothelial cell proliferation. In addition to being potential targets for antiangiogenesis tumor therapy, the expression patterns of these genes or their protein products may aid the development of pharmacodynamic assays for small molecule inhibitors of the KDR kinase in human tumors.

Rapamycin is active against B-precursor leukemia in vitro and in vivo, an effect that is modulated by IL-7-mediated signaling.

A balance between survival and apoptotic signals regulates B cell development. These signals are tightly regulated by a host of molecules, including IL-7. Abnormal signaling events may lead to neoplastic transformation of progenitor B cells. Signal transduction inhibitors potentially may modulate these abnormal signals. Inhibitors of the mammalian target of rapamycin (mTOR) such as rapamycin have been used as immunosuppressive agents. We hypothesized that rapamycin might demonstrate activity against B-precursor acute lymphoblastic leukemia. We have found that rapamycin inhibited growth of B-precursor acute lymphoblastic leukemia lines in vitro, with evidence of apoptotic cell death. This growth inhibition was reversible by IL-7. One candidate as a signaling intermediate cross-regulated by rapamycin and IL-7 was p70 S6 kinase. Rapamycin also demonstrated in vivo activity in E mu-ret transgenic mice, which develop pre-B leukemia/lymphoma: E mu-ret transgenic mice with advanced disease treated daily with rapamycin as a single agent showed a >2-fold increase in length of survival as compared with symptomatic littermates who received vehicle alone. These results suggest that mammalian target of rapamycin inhibitors may be effective agents against leukemia and that one of the growth signals inhibited by this class of drugs in precursor B leukemic cells may be IL-7-mediated.

Cytoplasmic micro heavy chain confers sensitivity to dexamethasone-induced apoptosis in early B-lineage acute lymphoblastic leukemia.

Most childhood acute lymphoblastic leukemia (ALL) arises from early B-lineage cells,and response to steroid treatment is critical to successful ALL therapy. To investigate the effect of the pre-B cell receptor (pre-BCR) complex on the response of leukemic cells to steroids, cytoplasmic micro protein (cyto mu) was transfected into cyto mu-, steroid-resistant early B cell lines. The presence of cyto mu and the assembled pre-BCR complex conferred sensitivity to dexamethasone-induced apoptosis. Both intrinsic and extrinsic apoptosis pathways are involved in this cell death. However, if the transfected cyto micro protein is unable to assemble the pre-BCR complex, the cells remain resistant to dexamethasone. These findings suggest a role for the pre-BCR complex in the response of ALL cells to treatment and provide insight into the mechanism of steroid response in the treatment of pre-B ALL.