718 WTX-124 is a novel IL-2 pro-drug that is conditionally activated in tumors and drives antitumor immunity in murine syngeneic cancer models

Background

Cancer immunotherapy has established itself as the fourth pillar of cancer treatment thanks to the clinical success of checkpoint inhibitors. However, durable anti-tumor responses following immunotherapy are still limited to certain cancer types, and only a fraction of patients respond to the treatment, demonstrating the need for additional immunotherapeutic agents. Preclinical and clinical studies have demonstrated the promise of cytokine therapy to increase antitumor immunity. One of these key cytokines, interleukin-2 (IL-2), is approved for clinical use in metastatic melanoma and renal cell carcinoma. Unfortunately, this treatment requires dosing every 8 hours due to its poor pharmacokinetic profile and is linked to serious toxicities which limits its utility.

Methods

To address these limitations, we designed WTX-124, an IL-2 pro-drug (IL-2 INDUKINE™ protein) that takes advantage of dysregulated protease activity in the tumor microenvironment (TME) to selectively deliver active IL-2 to the tumor after systemic administration. Peripheral inactivation is achieved by linking the cytokine to an inactivation domain using a tumor protease-sensitive linker. The INDUKINE™ molecule is also engineered with a half-life extension element to improve the pharmacokinetic profile and maintain longer exposure in the tumor. Once the IL-2 INDUKINE™ protein reaches the tumor, tumor-associated proteases cleave the linker and release the fully active cytokine.

Results

Treatment with WTX-124 resulted in the complete rejection of MC38 tumors in a manner dependent on proteolytic processing of the INDUKINE™ protein, as a non-cleavable version of WTX 124 lacked anti-tumor activity. Furthermore, the INDUKINE™ format greatly enhanced the PK profile of WTX 124 over free IL-2, resulting in greater exposure with less overall dosing, and demonstrating a favorable accumulation of free IL-2 in tumors compared to plasma. Mechanistically, WTX 124 treatment drove the expansion and activation of tumor infiltrating CD8+ T cells and NK cells which increased the production of effector cytokines in the tumor. This resulted in tumor rejection that translated into durable immune memory, as animals that rejected the tumors upon IL-2 INDUKINE™ protein treatment were protected against a subsequent re-challenge with the same tumor cells. WTX 124 also demonstrated favorable pharmacokinetic and tolerability characteristics in cynomolgus monkeys resulting in minimal release of IL-2 in the periphery.

Conclusions

The combination of tumor-selective activation of WTX-124 with reduced peripheral toxicities and its favorable pharmacokinetic profile supports moving this compound into clinical development.

Ethics Approval

All animal in vivo work was performed in accordance with current regulations and standards of the U.S. Department of Agriculture and the NIH.

715 WTX-330 is an IL-12 pro-drug that is conditionally activated within the tumor microenvironment and induces regressions in mouse tumor models

Background

Systemic administration of proinflammatory cytokines is a promising approach to treat cancer. However, poor pharmacokinetic properties and dose-limiting toxicities after systemic administration of cytokines such as interleukin 12 (IL-12) renders this strategy impractical. WTX-330 is a novel therapy identified using the Predator™ discovery platform that is designed to selectively deliver active wild-type IL-12 to the tumor microenvironment.

Methods

WTX-330 is an inducible polypeptide (INDUKINE™ molecule) that consists of wild-type IL-12 tethered to a high affinity antibody blockade domain and a half-life extension (HLE) domain via tumor protease-sensitive linkers.

Results

WTX-330 shows favorable inducible activity in vitro. WTX-330 incubated ex vivo with various primary human tumors led to the release of active IL-12, while WTX-330 was stable in human serum and normal tissues. Intraperitoneal (i.p.) administration of mouse WTX-330 led to complete tumor regression in multiple syngeneic tumor models. Importantly, equimolar amounts of wild-type IL-12, while active, was not tolerated by the mice compared to the IL-12 INDUKINE™ molecule. Mouse surrogate WTX-330 led to increased activation and frequencies of cross-presenting dendritic cells, NK cells and tumor specific CD8 T cells in B16F10 tumors. Moreover, mouse WTX-330, but not wild type IL-12, led to increased T cell activation specifically within B16F10 tumors as compared to the periphery. WTX-330 was well tolerated in non-human primates at different dose levels and schedules with exposure levels which exceeded the levels needed for anti-tumor activity in mice. In addition, there was low systemic exposure of IL-12 in the plasma after dosing with WTX-330 as compared to levels observed after treatment with wild-type IL-12.

Conclusions

Pharmacological and translational data obtained so far clearly support continued preclinical development with the goal of moving this innovative and differentiated engineered IL-12 therapy into human clinical testing.

Abstract 1723: WTX-124 is an IL-2 pro-drug conditionally activated in tumors and able to induce complete regressions in mouse tumor models

Cancer Immunotherapy has established itself as the fourth pillar of cancer treatment thanks to the clinical success of checkpoint inhibitors. Despite the durable responses achieved by some patients using these new therapies, the proportion of responders remains low and restricted to some cancer types. Preclinical and clinical studies have demonstrated the promise of cytokine therapy to increase antitumor immunity, however systemic toxicity and poor pharmacokinetic profiles have limited their clinical application. One of these key cytokines, interleukin-2 (IL-2), is approved for clinical use in metastatic melanoma and renal cell carcinoma. Unfortunately, this treatment is linked to serious toxicities which limits its utility. To address these limitations, our approach takes advantage of the dysregulated protease tumor microenvironment (TME) to activate an IL-2 pro-drug (IL-2 INDUKINETM) only at the desired site of activity. Peripheral inactivation is achieved by linking the cytokine to an inactivation domain using a tumor protease-sensitive linker. The INDUKINE is also engineered with a half-life extension element to improve tumor exposure. Once the IL-2 INDUKINETM reaches the tumor, tumor-associated proteases cleave the linker and release the active cytokine. This work presents data summarizing the discovery, biochemical, cellular, and in vivo activity of our lead IL-2 INDUKINETM WTX-124 and reviews the mechanism of action of these molecules. Treatment with WTX-124 results in complete regression of tumors driven by the expansion and activation of CD8+ T cells and NK cells which increases the production of effector cytokines in the tumor. Activity is dependent on the proteolytic processing of the INDUKINE as a non-cleavable control INDUKINE lacks efficacy. PK analysis in mouse models demonstrates a favorable accumulation of free IL-2 in tumors compared to plasma. The animals that rejected the tumors upon IL-2 INDUKINETM treatment were protected against follow up re-challenge with the same tumor cell line. In vitro proteolytic activation by human tumor samples will also be presented. The tumor-selective activation of WTX-124 with reduced peripheral toxicities supports its further clinical development.

Citation Format: Andres Salmeron, Heather Brodkin, Daniel Hicklin, Nesreen Ismail, Kristin Morris, Christopher Nirschl, Cynthia Seidel-Dugan, Philipp Steiner, Zoe Steuert, Jenna Sullivan, William Winston. WTX-124 is an IL-2 pro-drug conditionally activated in tumors and able to induce complete regressions in mouse tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1723.

[Shift Work and Sleep]

Shift Work and Sleep Abstract. Shift work and night work are necessary in our society today. In Europe, on average about 20 % of the working population work shifts; in Switzerland it is slightly lower at 14.7 %. The proportion of the working population who regularly work night shifts is much lower: 7 % of the working population in Europe and 5 % in Switzerland. The changed daily routine in night work and shift work leads to disturbances in our biological rhythms, which adapt only slowly to the new conditions. This often leads to a lack of sleep, poor sleep quality, reduced recovery and increased strain on the body. Moreover, the unusual working rhythms are not compatible with normal family and social life. It is important that as little shift and night work as possible is performed. Those affected and their environment should be aware of the disadvantages of shift and night work in particular and know how best to adapt to the specific work situation. There is much to suggest that lack of sleep and poor sleep quality are responsible for a large proportion of the negative effects of shift work. It is therefore important to ask specific questions in this area and offer concrete support to shift workers in this regard. This overview of shift work and sleep is based on literature and our many years of practical experience with shift work counselling and training in Switzerland.

Discovery of a novel ERK inhibitor with activity in models of acquired resistance to BRAF and MEK inhibitors

The high frequency of activating RAS or BRAF mutations in cancer provides strong rationale for targeting the mitogen-activated protein kinase (MAPK) pathway. Selective BRAF and MAP-ERK kinase (MEK) inhibitors have shown clinical efficacy in patients with melanoma. However, the majority of responses are transient, and resistance is often associated with pathway reactivation of the extracellular signal-regulated kinase (ERK) signaling pathway. Here, we describe the identification and characterization of SCH772984, a novel and selective inhibitor of ERK1/2 that displays behaviors of both type I and type II kinase inhibitors. SCH772984 has nanomolar cellular potency in tumor cells with mutations in BRAF, NRAS, or KRAS and induces tumor regressions in xenograft models at tolerated doses. Importantly, SCH772984 effectively inhibited MAPK signaling and cell proliferation in BRAF or MEK inhibitor-resistant models as well as in tumor cells resistant to concurrent treatment with BRAF and MEK inhibitors. These data support the clinical development of ERK inhibitors for tumors refractory to MAPK inhibitors.

Abstract 599: TMPRSS2-ERG gene fusion sensitizes VCaP human prostate tumors to the fully human anti-IGF-IR monoclonal antibody SCH 717454

A gene fusion of the androgen-regulated gene transmembrane protease, serine 2, (TMPRSS2) to the v-ets erythroblastosis virus E26 oncogene homolog (avian), ERG, of the erythroblast transformation-specific (ETS) family of transcription factors is a recently discovered genetic alteration in prostate cancer. Expression of the TMPRSS2-ERG fusion in prostate cancer patients is associated with an aggressive clinical phenotype and an early recurrence of the disease. Interestingly, in TMPRSS2-ERG positive prostate cancer cells, expression of this gene fusion is regulated by both estrogens and androgens. However, while the hormonal regulation of this fusion has been established the downstream effects of TPRSS2-ERG fusion gene have not been determined. Quantitative PCR analyses of 134 cancer cell lines, including 10 prostate cancer models, for expression of the TMPRSS2-ERG gene fusion showed that it was only present in VCaP, DuCaP, and NCI-H660 prostate cancer cells. We report here that VCaP human prostate cancer cells and tumor xenografts are sensitive to treatment with the fully human anti insulin-like growth factor-I receptor (IGF-IR) monoclonal antibody SCH 717454. After 28 days of treatment, single-agent SCH 717454 (0.5 mg, ip, 2 × week) caused complete inhibition of VCaP tumor growth. MDA PCa-2b, 22Rv1, DU-145, and LNCaP human prostate cancer tumor xenografts (negative for expression of the TMPRSS2-ERG gene fusion) did not respond to treatment with SCH 717454. Further, PTEN null NCI-H660 prostate tumors that also express the TMPRSS2-ERG gene fusion also did not respond to treatment with SCH 717454. When male SCID mice bearing established VCaP prostate cancer tumor xenografts were treated with the combination of surgical castration and SCH 717454 we observed 100% tumor regressions in all of the animals so that after 28 days of treatment there were no detectable tumors. When SCH 717454 was combined with the antiandrogen bicalutamide (50 mpk, po, bid), VCaP tumors regressed by 42%. That the combination of SCH 717454 and castration produced superior anti-tumor activity than the combination of SCH 717454 and bicalutamide provides further evidence that expression of the TMPRSS2-ERG gene fusion in VCaP prostate cancer tumors is regulated by both estrogens and androgens. TMPRSS2-ERG gene fusion expressing prostate cancer represents a new sub-classification of human prostate cancer. The precise role that the TMPRSS2-ERG fusion plays in the biology of human prostate cancer remains to be fully determined. These data indicate that PTEN wild-type VCaP prostate tumors that express the TMPRSS2-ERG gene fusion are sensitive to anti-IGF-IR treatment with SCH 717454 and that combining SCH 717454 with an androgen ablation therapy results in impressive anti-tumor activity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 599. doi:10.1158/1538-7445.AM2011-599

Inhibition of Both the Autocrine and the Paracrine Growth of Human Leukemia with a Fully Human Antibody Directed Against Vascular Endothelial Growth Factor Receptor 2

Vascular endothelial growth factor (VEGF) and its receptors (VEGFR) have been implicated in promoting solid tumor growth and metastasis via stimulating tumor-associated angiogenesis. Here we show that certain "liquid" tumors such as acute myeloid leukemia not only produce VEGF but also express functional VEGFR, resulting in an autocrine loop for tumor growth and propagation. In addition, the leukemia-derived VEGF can also stimulate the production of growth factors, including interleukin 6 (IL6) and granulocyte-macrophage colony stimulating factor (GM-CSF), by human endothelial cells, which in turn further promotes the growth of leukemia cells (the paracrine loop). A fully human anti-VEGFR2 (or kinase insert domain-containing receptor, KDR) antibody, IMC-2C6, strongly blocks KDR/VEGF interaction and neutralizes VEGF-stimulated activation of KDR in endothelial cells. In a system where leukemia cells are co-cultured with endothelial cells, IMC-2C6 inhibits both the production of IL6 and GM-CSF by endothelial cells and the growth of leukemia cells. Finally, IMC-2C6 effectively blocks VEGF-induced migration of KDR+ human leukemia cells, and when administered in vivo, significantly prolonged survival of mice inoculated with KDR+ human leukemia cells. Taken together, our data suggest that anti-KDR antibodies may have broad applications in the treatment of both solid tumors and certain types of leukemia.

Vascular endothelial growth factor receptor 3 is involved in tumor angiogenesis and growth

Vascular endothelial growth factor receptor 3 (VEGFR-3) binds VEGF-C and VEGF-D and is essential for the development of the lymphatic vasculature. Experimental tumors that overexpress VEGFR-3 ligands induce lymphatic vessel sprouting and enlargement and show enhanced metastasis to regional lymph nodes and beyond, whereas a soluble form of VEGFR-3 that blocks receptor signaling inhibits these changes and metastasis. Because VEGFR-3 is also essential for the early blood vessel development in embryos and is up-regulated in tumor angiogenesis, we wanted to determine if an antibody targeting the receptor that interferes with VEGFR-3 ligand binding can inhibit primary tumor growth. Our results show that antibody interference with VEGFR-3 function can inhibit the growth of several human tumor xenografts in immunocompromised mice. Immunohistochemical analysis showed that the blood vessel density of anti-VEGFR-3-treated tumors was significantly decreased and hypoxic and necrotic tumor tissue was increased when compared with tumors treated with control antibody, indicating that blocking of the VEGFR-3 pathway inhibits angiogenesis in these tumors. As expected, the anti-VEGFR-3-treated tumors also lacked lymphatic vessels. These results suggest that the VEGFR-3 pathway contributes to tumor angiogenesis and that effective inhibition of tumor progression may require the inhibition of multiple angiogenic targets.

VEGFR1-positive haematopoietic bone marrow progenitors initiate the pre-metastatic niche

The cellular and molecular mechanisms by which a tumour cell undergoes metastasis to a predetermined location are largely unknown. Here we demonstrate that bone marrow-derived haematopoietic progenitor cells that express vascular endothelial growth factor receptor 1 (VEGFR1; also known as Flt1) home to tumour-specific pre-metastatic sites and form cellular clusters before the arrival of tumour cells. Preventing VEGFR1 function using antibodies or by the removal of VEGFR1(+) cells from the bone marrow of wild-type mice abrogates the formation of these pre-metastatic clusters and prevents tumour metastasis, whereas reconstitution with selected Id3 (inhibitor of differentiation 3)-competent VEGFR1+ cells establishes cluster formation and tumour metastasis in Id3 knockout mice. We also show that VEGFR1+ cells express VLA-4 (also known as integrin alpha4beta1), and that tumour-specific growth factors upregulate fibronectin--a VLA-4 ligand--in resident fibroblasts, providing a permissive niche for incoming tumour cells. Conditioned media obtained from distinct tumour types with unique patterns of metastatic spread redirected fibronectin expression and cluster formation, thereby transforming the metastatic profile. These findings demonstrate a requirement for VEGFR1+ haematopoietic progenitors in the regulation of metastasis, and suggest that expression patterns of fibronectin and VEGFR1+VLA-4+ clusters dictate organ-specific tumour spread.

Induction of cutaneous delayed-type hypersensitivity reactions in VEGF-A transgenic mice results in chronic skin inflammation associated with persistent lymphatic hyperplasia

Vascular endothelial growth factor-A (VEGF-A) expression is up-regulated in several inflammatory diseases including psoriasis, delayed-type hypersensitivity (DTH) reactions, and rheumatoid arthritis. To directly characterize the biologic function of VEGF-A in inflammation, we evaluated experimental DTH reactions induced in the ear skin of transgenic mice that overexpress VEGF-A specifically in the epidermis. VEGF-A transgenic mice underwent a significantly increased inflammatory response that persisted for more than 1 month, whereas inflammation returned to baseline levels within 7 days in wild-type mice. Inflammatory lesions in VEGF-A transgenic mice closely resembled human psoriasis and were characterized by epidermal hyperplasia, impaired epidermal differentiation, and accumulation of dermal CD4+ T-lymphocytes and epidermal CD8+ lymphocytes. Surprisingly, VEGF-A also promoted lymphatic vessel proliferation and enlargement, which might contribute to the increased inflammatory response, as lymphatic vessel enlargement was also detected in human psoriatic skin lesions. Combined systemic treatment with blocking antibodies against VEGF receptor-1 (VEGFR-1) and VEGFR-2 potently inhibited inflammation and also decreased lymphatic vessel size. Together, these findings reveal a central role of VEGF-A in promoting lymphatic enlargement, vascular hyperpermeability, and leukocyte recruitment, thereby leading to persistent chronic inflammation. They also indicate that inhibition of VEGF-A bioactivity might be a new approach to anti-inflammatory therapy.

Differences in therapeutic indexes of combination metronomic chemotherapy and an anti-VEGFR-2 antibody in multidrug-resistant human breast cancer xenografts

One of the greatest barriers to the treatment of cancer with chemotherapeutic drugs is acquisition of drug resistance. This includes multidrug resistance mediated by P-glycoprotein (Pgp) to multiple lipophilic natural compounds such as taxanes, doxorubicin (Adriamycin), and vinblastine. The considerable efforts made thus far to reverse this and other types of drug resistance have had very limited success. We report here that a variety of orthotopic human breast cancer xenografts selected for high levels of Pgp and multidrug resistance respond in a significant and durable manner to different continuous low-dose (e.g., one-tenth the maximum tolerated dose of chemotherapy) chemotherapy regimens, when used in combination with an antivascular endothelial cell growth factor (anti-VEGF) receptor-2 (flk-1)-neutralizing antibody (DC101). The Pgp substrates paclitaxel (Taxol), Adriamycin, and vinblastine were all effective using this type of combination treatment, although the chemotherapy protocols showed little or no effect as monotherapies. Similar results were also obtained using cisplatinum (a non-Pgp substrate drug) against cisplatinum-resistant tumors. Evidence of significant tumor cell death by the combination treatment was detected within 3 weeks of initiation of therapy by histopathological analysis, in the absence of shrinkage of tumor mass. There were, however, marked differences in the cumulative toxicity of long-term regimens of Adriamycin and cisplatinum, where toxicity was observed, when compared with the tubulin inhibitors, vinblastine and Taxol, where it was not. We conclude that vascular-targeting protocols involving frequent administration of very low doses of certain chemotherapeutic drugs can provide a stable and safe way to circumvent multidrug resistance in established orthotopically growing tumors, as long as these are used in combination with a second antiangiogenic drug, in this case, anti-VEGFR-2 blocking antibodies.

Impaired recruitment of bone-marrow-derived endothelial and hematopoietic precursor cells blocks tumor angiogenesis and growth

The role of bone marrow (BM)-derived precursor cells in tumor angiogenesis is not known. We demonstrate here that tumor angiogenesis is associated with recruitment of hematopoietic and circulating endothelial precursor cells (CEPs). We used the angiogenic defective, tumor resistant Id-mutant mice to show that transplantation of wild-type BM or vascular endothelial growth factor (VEGF)-mobilized stem cells restore tumor angiogenesis and growth. We detected donor-derived CEPs throughout the neovessels of tumors and Matrigel-plugs in an Id1+/-Id3-/- host, which were associated with VEGF-receptor-1-positive (VEGFR1+) myeloid cells. The angiogenic defect in Id-mutant mice was due to impaired VEGF-driven mobilization of VEGFR2+ CEPs and impaired proliferation and incorporation of VEGFR1+ cells. Although targeting of either VEGFR1 or VEGFR2 alone partially blocks the growth of tumors, inhibition of both VEGFR1 and VEGFR2 was necessary to completely ablate tumor growth. These data demonstrate that recruitment of VEGF-responsive BM-derived precursors is necessary and sufficient for tumor angiogenesis and suggest new clinical strategies to block tumor growth.

Acquired resistance to the antitumor effect of epidermal growth factor receptor-blocking antibodies in vivo: a role for altered tumor angiogenesis

Inhibitors of epidermal growth factor receptor (EGFR) signaling are among the novel drugs showing great promise for cancer treatment in the clinic. However, the possibility of acquired resistance to such drugs because of tumor cell genetic instabilities has not yet been explored. Here we report the experimental derivation and properties of such cell variants obtained from recurrent tumor xenografts of the human A431 squamous cell carcinoma, after two consecutive cycles of therapy with one of three different anti-EGFR monoclonal antibodies: mR3, hR3, or C225. Initial response to a 2-week period of treatment was generally total tumor regression and was not significantly different among the three antibody groups. However, tumors often reappeared at the site of inoculation, generally after prolonged latency periods, and most of the tumors became refractory to a second round of therapy. Cell lines established from such resistant tumors retained high EGFR expression, normal sensitivity to anti-EGFR antibody or ligand, and unaltered growth rate when compared with the parental line in vitro. In contrast, the A431 cell variants exhibited an accelerated growth rate and a significantly attenuated response to anti-EGFR antibodies in vivo relative to the parental line. Because of the reported suppressive effect of EGFR inhibitors on vascular endothelial growth factor (VEGF) expression, and the demonstrated role of VEGF in the angiogenesis and growth of A431 tumor xenografts, relative VEGF expression was examined. Five of six resistant variants expressed increased levels of VEGF, which paralleled an increase in both angiogenic potential in vitro and tumor angiogenesis in vivo. In addition, elevated expression of VEGF in variants of A431 cells obtained by gene transfection rendered the cells significantly resistant to anti-EGFR antibodies in vivo. Taken together, the results suggest that, at least in the A431 system, variants displaying acquired resistance to anti-EGFR antibodies can emerge in vivo and can do so, at least in part, by mechanisms involving the selection of tumor cell subpopulations with increased angiogenic potential.

Vascular trauma induces rapid but transient mobilization of VEGFR2(+)AC133(+) endothelial precursor cells

Bone marrow (BM)-derived circulating endothelial precursor cells (CEPs) are thought to play a role in postnatal angiogenesis. Emerging evidence suggests that angiogenic stress of vascular trauma may induce mobilization of CEPs to the peripheral circulation. In this regard, we studied the kinetics of CEP mobilization in two groups of patients who experienced acute vascular insult secondary to burns or coronary artery bypass grafting (CABG). In both burn and CABG patients, there was a consistent, rapid increase in the number of CEPs, determined by their surface expression pattern of vascular endothelial growth factor receptor 2 (VEGFR2), vascular endothelial cadherin (VE-cadherin), and AC133. Within the first 6 to 12 hours after injury, the percentage of CEPs in the peripheral blood of burn or CABG patients increased almost 50-fold, returning to basal levels within 48 to 72 hours. Mobilized cells also formed late-outgrowth endothelial colonies (CFU-ECs) in culture, indicating that a small, but significant, number of circulating endothelial cells were BM-derived CEPs. In parallel to the mobilization of CEPs, there was also a rapid elevation of VEGF plasma levels. Maximum VEGF levels were detected within 6 to 12 hours of vascular trauma and decreased to baseline levels after 48 to 72 hours. Acute elevation of VEGF in the mice plasma resulted in a similar kinetics of mobilization of VEGFR2(+) cells. On the basis of these results, we propose that vascular trauma may induce release of chemokines, such as VEGF, that promotes rapid mobilization of CEPs to the peripheral circulation. Strategies to improve the mobilization and incorporation of CEPs may contribute to the acceleration of vascularization of the injured vascular tissue.

Hematopoietic activity of a stromal cell transmembrane protein containing epidermal growth factor-like repeat motifs

Primitive hematopoietic stem cells are closely associated with discrete in vivo microenvironments. These "niches" are thought to provide the molecular signals that mediate stem cell differentiation and self-renewal. We have dissected the fetal liver microenvironment into distinct cellular components by establishing an extensive panel of stromal cell lines. One particular cell line maintains repopulating stem cells for prolonged in vitro culture periods. A subtraction cloning strategy has yielded a cDNA that encodes a cell surface glycoprotein with a restricted pattern of expression among stromal cell lines. This molecule, previously identified as delta-like/preadipocyte factor-1, contains epidermal growth factor-like repeats that are related to those in the notch/delta/serrate family of proteins. We have investigated the potential role of this molecule in hematopoietic stem/progenitor cell regulation. We show that the delta-like protein displays activity on purified stem cells by promoting the formation of "cobblestone areas" of proliferation. These cobblestone areas contain both primitive high-proliferative potential progenitors and in vivo repopulating stem cells.

High-level expression of a biologically active human interleukin-6 mutein

We have constructed two different muteins of interleukin-6 (IL-6) which were expressed in Escherichia coli. Both muteins lack the first 22 N-terminal amino acids of native IL-6 and lack one or the other of the two naturally occurring pairs of cysteines at either position 45 and 51 or position 74 and 84 of IL-6. We found that there was a dramatic increase in the level of IL-6 produced from each mutein clone, compared to the level produced by the wild-type IL-6 clone. We also observed that the yield of soluble and properly refolded mutein IL-6 was highest when the cysteines at position 74 and 84 were left intact. The mutein IL-6 with cysteines at position 74 and 84 was as active as wild-type IL-6 and a lower concentration of the mutein IL-6 was required to reach maximal activity, compared to wild-type IL-6. The mutein IL-6 with cysteines at position 45 and 51 had a much reduced biological activity.

Heparin modulates the interaction of VEGF165 with soluble and cell associated flk-1 receptors

The 165-amino acid form of vascular endothelial growth factor (VEGF165) is a mitogen for vascular endothelial cells and a potent angiogenic factor. Expression of a chimeric receptor containing the extracellular domain of the flk-1 receptor fused to the transmembrane and intracellular domains of the human c-fms receptor in NIH-3T3 cells, resulted in the appearance of high affinity binding sites for 125I-VEGF165 on transfected cells. The binding of 125I-VEGF165 to the flk-1/fms chimeric receptor of the transfected cells as well as the VEGF165-induced autophosphorylation of the chimeric receptors were inhibited in the presence of low concentrations of heparin (1-10 micrograms/ml). In contrast, similar concentrations of heparin potentiated the binding of 125I-VEGF165 to the endogenous VEGF receptors of the transfected cells, indicating that to some extent, the effect of heparin on 125I-VEGF165 binding is receptor type-dependent. A soluble fusion protein containing the extracellular domain of flk-1 fused to alkaline phosphatase (flk-1/SEAP) was used to study the effects of heparin on the binding of 125I-VEGF165 to flk-1 in a cell-free environment. The fusion protein specifically inhibited VEGF165-induced proliferation of vascular endothelial cells, but bound 125I-VEGF165 inefficiently in the absence of heparin. Addition of low concentrations of heparin or heparan sulfate (0.1-1 microgram/ml) resulted in a strong potentiation of 125I-VEGF165 binding, whereas higher heparin or heparan sulfate concentrations inhibited the binding. The effect of heparin on the binding of 125I-VEGF165 to flk-1/SEAP could not be mimicked by desulfated heparin or by chondroitin sulfate. Both bFGF and aFGF inhibited the binding when low concentrations of heparin were added to the binding reaction. However, higher concentrations of heparin abolished the inhibition, indicating that the inhibition is probably caused by competition for available heparin. Taken as a whole, these results indicate that heparin-like molecules regulate the binding of VEGF165 to its receptors in complex ways which depend on the heparin binding properties of VEGF165, on the specific VEGF receptor type involved, and on the amount and composition of heparin-like molecules that are present on the cell surface of VEGF receptor containing cells.

Expression of basic fibroblast growth factor in normal human tissues

The distribution of basic fibroblast growth factor (bFGF) was studied immunohistochemically in fresh frozen sections of normal human tissues. Immunodetection was performed with a specific anti-bFGF mouse monoclonal antibody that was found to react with recombinant human bFGF in Western blot analysis, and to specifically neutralize the mitogenic activity of bFGF on bovine vascular endothelial cells. Expression of bFGF on normal human tissues was ubiquitously detected in the basement membranes of all size blood vessels, but was not found in epidermal or epithelial basement membranes of a variety of tissues tested. Intensity and patterns of localization in blood vessels was consistent in various tissues, but varied among different regions of the vascular bed. Whereas homogeneous and intense immunoreactivity were observed in large and intermediate size blood vessels, heterogeneity of expression was found in capillaries. The most intense immunoreactivity was observed in branching capillaries. Endothelial cell staining was heterogeneous and varied in different regions. Strong staining for bFGF was also found in cardiac muscle fibers, smooth muscle cells of mid-size blood vessels, the gut and the myometrium, in central nervous system neurons and cerebellar Purkinje cells, and on epithelial cells of the bronchi, colon, endometrium, and sweat gland ducts of the skin. The presence of bFGF in the extracellular compartment of a diverse variety of organs may play a role in angiogenesis. However, the function of bFGF in parenchymal cells remains to be determined.

Social support and immune function among spouses of cancer patients

This study investigated whether social support was related to immune function among spouses of cancer patients. Effects of depression and negative life events were examined as potential mediators. Results showed evidence of greater immunocompetence on 2 of 3 dynamic measures: natural killer cytotoxicity and proliferation response to phytohemagglutinin among spouses who reported high levels of social support. All six components of social support assessed by the Social Provisions Scale (Cutrona & Russell, 1987) were strongly related to these indices of immune function. No evidence was found for mediation by either life events or depression.

Social support and immune function among spouses of cancer patients

This study investigated whether social support was related to immune function among spouses of cancer patients. Effects of depression and negative life events were examined as potential mediators. Results showed evidence of greater immunocompetence on 2 of 3 dynamic measures: natural killer cytotoxicity and proliferation response to phytohemagglutinin among spouses who reported high levels of social support. All six components of social support assessed by the Social Provisions Scale (Cutrona & Russell, 1987) were strongly related to these indices of immune function. No evidence was found for mediation by either life events or depression.