Biomedical subjects

David Huso

Publications and source records attributed to David Huso.

6 recordsLinked to original sources

PubMed2006

IMC-EB10, an anti-FLT3 monoclonal antibody, prolongs survival and reduces nonobese diabetic/severe combined immunodeficient engraftment of some acute lymphoblastic leukemia cell lines and primary leukemic samples.

The class III receptor tyrosine kinase FLT3 is expressed on the blasts of >90% of patients with B-lineage acute lymphoblastic leukemias (ALL). In addition, it is expressed at extremely high levels in ALL patients with mixed lineage leukemia rearrangements or hyperdiploidy and is sometimes mutated in these same patients. In this report, we investigate the effects of treating ALL cell lines and primary samples with human anti-FLT3 monoclonal antibodies (mAb) capable of preventing binding of FLT3 ligand. In vitro studies, examining the ability of two anti-FLT3 mAbs (IMC-EB10 and IMC-NC7) to affect FLT3 activation and downstream signaling in ALL cell lines and primary blasts, yielded variable results. FLT3 phosphorylation was consistently inhibited by IMC-NC7 treatment, but in some cell lines, IMC-EB10 actually stimulated FLT3 activation, possibly as a result of antibody-mediated receptor dimerization. Through antibody-dependent, cell-mediated cytotoxicity, such an antibody could still prove efficacious against leukemia cells in vivo. In fact, IMC-EB10 treatment significantly prolonged survival and/or reduced engraftment of several ALL cell lines and primary ALL samples in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. This occurred even when IMC-EB10 treatment resulted in FLT3 activation in vitro. Moreover, fluorescence-activated cell sorting and PCR analysis of IMC-EB10-treated NOD/SCID mice surviving 150 days post-leukemic cell injection revealed that FLT3 immunotherapy reduced leukemic engraftment below the level of detection in these assays (<0.001%). Furthermore, in vivo IMC-EB10 treatment did not select for resistant cells, because cells surviving IMC-EB10 treatment remain sensitive to IMC-EB10 cytotoxicity upon retransplantation. In vivo studies involving either partial depletion or activation of natural killer (NK) cells show that most of the cytotoxic effect of IMC-EB10 is mediated through NK cells. Therefore, such an antibody, either naked or conjugated to radioactive isotopes or cytotoxic agents, may prove useful in the therapy of infant ALL as well as childhood and adult ALL patients whose blasts typically express FLT3.

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PubMed2006

Ductal access for prevention and therapy of mammary tumors.

In cancer patients and in those at high risk, systemic exposure to agents for therapy or prevention is accompanied by undesirable side effects. We hypothesized that it is possible to prevent and treat breast cancer by introducing anticancer agents into the mammary ductal network. Here, we show the efficacy of intraductally administered anticancer agents 4-hydroxytamoxifen and pegylated liposomal doxorubicin (PLD) in the prevention and treatment of breast cancer using the rat N-methyl-N'-nitrosourea-induced and spontaneous HER-2/neu transgenic mouse (neu-N) models of breast cancer. Intraductal administration of PLD to neu-N mice caused regression of established tumors and prevented tumor development more effectively than i.v. injection (P < 0.0001). Intraductal administration resulted in lower circulating levels of PLD compared with i.v. administration, with no evidence of systemic toxicity or long-term histopathologic changes in the mammary gland. Compared with systemic administration, intraductal injection provides direct access to breast lesions with higher local and lower systemic drug exposure. These studies suggest that this approach has potential for application to prevention and neoadjuvant therapy of early breast cancer.

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PubMed2005

Short telomeres, even in the presence of telomerase, limit tissue renewal capacity.

Autosomal-dominant dyskeratosis congenita is associated with heterozygous mutations in telomerase. To examine the dosage effect of telomerase, we generated a line of mTR+/- mice on the CAST/EiJ background, which has short telomeres. Interbreeding of heterozygotes resulted in progressive telomere shortening, indicating that limiting telomerase compromises telomere maintenance. In later-generation heterozygotes, we observed a decrease in tissue renewal capacity in the bone marrow, intestines, and testes that resembled defects seen in dyskeratosis congenita patients. The progressive worsening of disease with decreasing telomere length suggests that short telomeres, not telomerase level, cause stem cell failure. Further, wild-type mice derived from the late-generation heterozygous parents, termed wt*, also had short telomeres and displayed a germ cell defect, indicating that telomere length determines these phenotypes. We propose that short telomeres in mice that have normal telomerase levels can cause an occult form of genetic disease.

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PubMed2005

Inhibitory anti-FLT3 antibodies are capable of mediating antibody-dependent cell-mediated cytotoxicity and reducing engraftment of acute myelogenous leukemia blasts in nonobese diabetic/severe combined immunodeficient mice.

Aberrant FLT3 expression and/or mutation plays a significant role in leukemogenesis. This has prompted the development of selective small molecule tyrosine kinase inhibitors against FLT3. However, like most tyrosine kinase inhibitors, those against FLT3 are not completely specific and at the doses required to completely inhibit target, significant toxicities may occur. In addition, tyrosine kinase inhibitors for other kinases have been shown to select for cells that become resistant. To overcome some of these limitations we developed two fully human phage display monoclonal antibodies against FLT3 (IMC-EB10 and IMC-NC7). These antibodies inhibited ligand-mediated activation of wild-type FLT3 and constitutively activated mutant FLT3 and in most cell types affected downstream STAT5, AKT, and mitogen-activated protein kinase activation. In addition to interfering with FLT3 signaling, IMC-EB10 and, to a significantly lesser extent, IMC-NC7 initiated antibody-dependent cell-mediated cytotoxicity on FLT3-expressing cells. When IMC-EB10 was used in vivo to treat nonobese diabetic/severe combined immunodeficient mice given injections of primary FLT3/ITD acute myelogenous leukemia samples or myeloid cell lines with FLT3 expression, it significantly decreased engraftment of leukemic cells and increased survival, respectively. In contrast, IMC-EB10 treatment did not reduce engraftment of normal human CD34+ cord blood cells nor did it show any significant inhibition of normal murine hematopoiesis. Thus, these types of antibodies have the potential to be safe and effective new therapeutic agents for acute myelogenous leukemia and possibly other FLT3-expressing malignancies.

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PubMed2004

HIV-1 transgenic rats develop T cell abnormalities.

HIV-1 infection leads to impaired antigen-specific T cell proliferation, increased susceptibility of T cells to apoptosis, progressive impairment of T-helper 1 (Th1) responses, and altered maturation of HIV-1-specific memory cells. We have identified similar impairments in HIV-1 transgenic (Tg) rats. Tg rats developed an absolute reduction in CD4+ and CD8+ T cells able to produce IFN-gamma following activation and an increased susceptibility of T cells to activation-induced apoptosis. CD4+ and CD8+ effector/memory (CD45RC- CD62L-) pools were significantly smaller in Tg rats compared to non-Tg controls, although the converse was true for the naïve (CD45RC+ CD62L+) T cell pool. Our interpretation is that the HIV transgene causes defects in the development of T cell effector function and generation of specific effector/memory T cell subsets, and that activation-induced apoptosis may be an essential factor in this process.

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PubMed2004

Targeting vascular and avascular compartments of tumors with C. novyi-NT and anti-microtubule agents.

Current approaches for treating cancer are limited, in part, by the inability of drugs to affect the poorly vascularized regions of tumors. We have found that C. novyi-NT in combination with anti-microtubule agents can cause the destruction of both the vascular and avascular compartments of tumors. The two classes of microtubule inhibitors were found to exert markedly different effects. Some agents that inhibited microtubule synthesis, such as HTI-286 and vinorelbine, caused rapid, massive hemorrhagic necrosis when used in combination with C. novyi-NT. In contrast, agents that stabilized microtubules, such as the taxanes docetaxel and MAC-321, resulted in slow tumor regressions that killed most neoplastic cells. Remaining cells in the poorly perfused regions of tumors could be eradicated by C. novyi-NT. Mechanistic studies showed that the microtubule destabilizers, but not the microtubule stabilizers, radically reduced blood flow to tumors, thereby enlarging the hypoxic niche in which C. novyi-NT spores could germinate. A single intravenous injection of C. novyi-NT plus selected anti-microtubule agents was able to cause regressions of several human tumor xenografts in nude mice in the absence of excessive toxicity.

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