Keith Alcorn

Bio: Keith Alcorn is an academic researcher from University of Pennsylvania. The author has contributed to research in topics: Phosphorylation & Sirolimus. The author has an hindex of 1, co-authored 1 publications receiving 154 citations.

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

Abstract: 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 Eμ-ret transgenic mice, which develop pre-B leukemia/lymphoma: Eμ-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.

‘His utter unfitness for a commercial collector’

Abstract: Non-European or ‘exotic’ plants became prestigious collectable items in the early nineteenth century. Although unpaid collectors contributed greatly to the discovery of new plants, systematic sponsored collecting became increasingly important after 1800 in Britain. While sharing features of natural history collecting, the organization and sponsorship of exotic plant collecting in the first half of the nineteenth century in Britain exhibits several distinctive features, notably the involvement of commercial sponsors and cooperation between commercial and scientific bodies. Using the Directors’ Correspondence of the Royal Botanic Gardens, Kew, this article describes how individuals, consortia of sponsors and subscription systems assembled finance for plant collecting. The article demonstrates the extent to which plant introductions depended on a structured trade in plants, in which commercial nurseries played a central role. Plant collecting must be understood as an episode not only in the history of garden design, but also in the history of collections.

Natural products for cancer chemotherapy

Abstract: For over 40 years, natural products have served us well in combating cancer. The main sources of these successful compounds are microbes and plants from the terrestrial and marine environments. The microbes serve as a major source of natural products with anti‐tumour activity. A number of these products were first discovered as antibiotics. Another major contribution comes from plant alkaloids, taxoids and podophyllotoxins. A vast array of biological metabolites can be obtained from the marine world, which can be used for effective cancer treatment. The search for novel drugs is still a priority goal for cancer therapy, due to the rapid development of resistance to chemotherapeutic drugs. In addition, the high toxicity usually associated with some cancer chemotherapy drugs and their undesirable side‐effects increase the demand for novel anti‐tumour drugs active against untreatable tumours, with fewer side‐effects and/or with greater therapeutic efficiency. This review points out those technologies needed to produce the anti‐tumour compounds of the future.

Harnessing the biology of IL-7 for therapeutic application

Abstract: Interleukin-7 (IL-7) is required for T cell development and for maintaining and restoring homeostasis of mature T cells. IL-7 is a limiting resource under normal conditions, but it accumulates during lymphopaenia, leading to increased T cell proliferation. The administration of recombinant human IL-7 to normal or lymphopenic mice, non-human primates and humans results in widespread T cell proliferation, increased T cell numbers, modulation of peripheral T cell subsets and increased T cell receptor repertoire diversity. These effects raise the prospect that IL-7 could mediate therapeutic benefits in several clinical settings. This Review summarizes the biology of IL-7 and the results of its clinical use that are available so far to provide a perspective on the opportunities for clinical application of this cytokine.

Posttransplant lymphoproliferative disorders after renal transplantation in the United States in era of modern immunosuppression

Abstract: Background Posttransplant lymphoproliferative disorders (PTLD) still represent a major preoccupation after renal transplantation, even in the most recent years. Methods We analyzed the incidence, risk, and prognostic factors of PTLD in a cohort of kidney recipients using the United States Renal Data System. Results Among 25,127 Medicare patients transplanted between 1996 and 2000, 344 developed a PTLD defined as a non-Hodgkin lymphoma (1.4%). History of pretransplant malignancy (adjusted hazard ratio [AHR]=3.54, CI 2.31-5.43), younger age (AHR=1.91, CI 1.18-3.1), fewer HLA matches (AHR=1.32, CI 1.1-1.59) and treatment by ATG (AHR=1.55, CI 1.2-1.99) and OKT3 (AHR=1.37, CI 1-1.76), especially if given for rejection therapy were associated with an increased risk of PTLD. Mycophenolate and azathioprine were associated with a lower risk of PTLD (AHR=0.6, CI 0.47-0.78 and AHR=0.66, CI 0.46-0.95, respectively). IL2-receptor inhibitors and sirolimus did not modify the risk of PTLD. Patients without induction therapy treated with tacrolimus were at greater risk of lymphoma than those treated with new formulations of cyclosporine and those treated with antimetabolites (mycophenolate and azathioprine) have a lower risk of PTLD than those without. Patients with PTLD had poor survival (64% vs. 80% at 5 years). Older age, pretransplant malignancy and OKT3 were risk factors for death whereas treatment with mycophenolate was associated with a better survival (AHR=0.49, CI=0.28-0.82). Conclusions Our study highlights the contribution of patient history and immunosuppression in the risk of PTLD in the era of modern immunosuppression.

A role for mammalian target of rapamycin in regulating T cell activation versus anergy.

Abstract: Whether TCR engagement leads to activation or tolerance is determined by the concomitant delivery of multiple accessory signals, cytokines, and environmental cues. In this study, we demonstrate that the mammalian target of rapamycin (mTOR) integrates these signals and determines the outcome of TCR engagement with regard to activation or anergy. In vitro, Ag recognition in the setting of mTOR activation leads to full immune responses, whereas recognition in the setting of mTOR inhibition results in anergy. Full T cell activation is associated with an increase in the phosphorylation of the downstream mTOR target S6 kinase 1 at Thr(421)/Ser(424) and an increase in the mTOR-dependent cell surface expression of transferrin receptor (CD71). Alternatively, the induction of anergy results in markedly less S6 kinase 1 Thr(421)/Ser(424) phosphorylation and CD71 surface expression. Likewise, the reversal of anergy is associated not with proliferation, but rather the specific activation of mTOR. Importantly, T cells engineered to express a rapamycin-resistant mTOR construct are resistant to anergy induction caused by rapamycin. In vivo, mTOR inhibition promotes T cell anergy under conditions that would normally induce priming. Furthermore, by examining CD71 surface expression, we are able to distinguish and differentially isolate anergic and activated T cells in vivo. Overall, our data suggest that by integrating environmental cues, mTOR plays a central role in determining the outcome of Ag recognition.

Overcoming cancer therapeutic bottleneck by drug repurposing

Abstract: Ever present hurdles for the discovery of new drugs for cancer therapy have necessitated the development of the alternative strategy of drug repurposing, the development of old drugs for new therapeutic purposes. This strategy with a cost-effective way offers a rare opportunity for the treatment of human neoplastic disease, facilitating rapid clinical translation. With an increased understanding of the hallmarks of cancer and the development of various data-driven approaches, drug repurposing further promotes the holistic productivity of drug discovery and reasonably focuses on target-defined antineoplastic compounds. The “treasure trove” of non-oncology drugs should not be ignored since they could target not only known but also hitherto unknown vulnerabilities of cancer. Indeed, different from targeted drugs, these old generic drugs, usually used in a multi-target strategy may bring benefit to patients. In this review, aiming to demonstrate the full potential of drug repurposing, we present various promising repurposed non-oncology drugs for clinical cancer management and classify these candidates into their proposed administration for either mono- or drug combination therapy. We also summarize approaches used for drug repurposing and discuss the main barriers to its uptake.