Numerical evaluation reveals the effect of branching morphology on vessel transport properties during angiogenesis

Blood flow governs transport of oxygen and nutrients into tissues. Hypoxic tissues secrete VEGFs to promote angiogenesis during development and in tissue homeostasis. In contrast, tumors enhance pathologic angiogenesis during growth and metastasis, suggesting suppression of tumor angiogenesis could limit tumor growth. In line with these observations, various factors have been identified to control vessel formation in the last decades. However, their impacts on the vascular transport properties of oxygen remain elusive. Here, we take a computational approach to examine the effects of vascular branching on blood flow in the growing vasculature. First of all, we reconstruct a 3D vascular model from the 2D confocal images of the growing vasculature at postnatal day 5 (P5) mouse retina, then simulate blood flow in the vasculatures, which are obtained from the gene targeting mouse models causing hypo- or hyper-branching vascular formation. Interestingly, hyper-branching morphology attenuates effective blood flow at the angiogenic front, likely promoting tissue hypoxia. In contrast, vascular hypo-branching enhances blood supply at the angiogenic front of the growing vasculature. Oxygen supply by newly formed blood vessels improves local hypoxia and decreases VEGF expression at the angiogenic front during angiogenesis. Consistent with the simulation results indicating improved blood flow in the hypo-branching vasculature, VEGF expression around the angiogenic front is reduced in those mouse retinas. Conversely, VEGF expression is enhanced in the angiogenic front of hyper-branching vasculature. Our results indicate the importance of detailed flow analysis in evaluating the vascular transport properties of branching morphology of the blood vessels.

Blood vessels are important for the transport of various substances, such as oxygen, nutrients, and cells, to the entire body. Control of blood vessel formation is thought to be important in health and disease. In the last decades, various factors which regulate blood vessel branching morphology have been identified. Gene modification of some of these identified factors results in hyper-branching of the vasculature while others cause hypo-branching of the vessel. Given the importance of the transport property of the blood vessel, it is important to examine the effect of these identified factors on the transport property of the affected vascular morphology. In line with these facts, we reconstruct 3D vessel structures from 2D confocal microscopy images. We then numerically simulate blood flow in the structures. Interestingly, our results suggest vessel network complexity negatively affects the blood perfusion efficiency and tissue oxygenation during angiogenesis. Thus, our results highlight the importance of flow analysis considering the detailed 3D branching pattern of the vascular network to quantitatively evaluate its transport properties.

Abstract P5-01-11: A new anti-HER2 peptide “CH401MAP” can stimulate the immunity of breast cancer patients

In previous decades, numerous attempts have been made to develop therapeutic peptide vaccines for cancer. However, the HLA (Human Leukocyte Antigen) types are limited because most peptide vaccines are specific to the major HLA types of the area. Peptide vaccines specific for Caucasians thus may not be specific to Japanese. Moreover, they are not designed to stimulate both helper and killer T cells. We are trying to make a peptide vaccine specific to the MHC of Japanese patients that stimulates both helper and killer T cells. We selected a new-HER2 peptide including a B-cell epitope which has anti-tumor effects in a mouse system. The B-cell epitope was determined for a H401 monoclonal antibody (mAb) specific for HER2. As for epitope mapping of the chimera mAb CH401, enzyme-linked immunosorbent assay was employed with 20mer MAPs carrying a partial HER2 sequence. The CH401 epitope was determined as N:163-182, and the CH401MAP including the epitope induced anti-tumor effects in HER2-overexpressing tumor cells in a mouse system. We predicted the peptide MHC affinity and examined the in vitro reaction of PBMCs from Japanese breast cancer patients. The study enrolled 173 female breast cancer patients who underwent surgery between October 2010 and July 2012 at Tokai University Hospital. We used SYFPEITHI, BIMAS and IEDB algorithms to estimate peptide and HLA affinity. Lymphocyte proliferation ability, cell surface marker expression, cytokine (interleukin (IL)-2, IL-4 and interferon (IFN)-g) secretion and specific antibody production were analyzed in vitro. According to the algorithms, 97.1% of patients showed high to intermediate affinity of the CH401 epitope peptide to Japanese major HLA class I. Similarly, 34.5% of patients showed high to moderate affinity to HLA class II. The proliferative ability of patient groups was significantly higher than that of the HD group (HER2 0 group, p<0.05; HER2 1+2+ group, p<0.01; HER2 3+ group, p<0.01). Cell percentages of CD8+ cells were significantly increased after 21 days of CH401MAP stimulation. In the HER2 0 patient group, CD4+CD25+ cell ratio was also increased, while no significant increase was seen in the other groups. Foxp-3 expression was not increased in any groups, suggesting that these cells were not regulatory T cells. Concentrations of IL2 in stimulated supernatant tended to increase in all patient groups. In particular, concentration in the HER2 1+2+ group at 48 h was significantly increased (p<0.001). IL-4 and IFN-g secretion also tended to increase. CH401MAP-specific antibodies were measured for all breast cancer patient groups and HD, showing significant differences. However, within each patients’ group, no significant differences were observed irrespective of CH401MAP stimulation (p<0.001). As a result, reactivity with CH401MAP and breast cancer patient PBMCs activated immunity in the total breast cancer patient group, and the association with HER2 expression level of the primary cancer was poor overall. Collectively, CH401MAP may become a promising peptide vaccine to prevent recurrent breast cancer in Japanese patients.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-01-11.

Ex vivo evidence for asymmetric tyrosine phosphorylation of ZAP-70 on double-positive thymocytes in the positive selection process

Antigen stimulation via TCR in mature T cells provides rapid induction of tyrosine phosphorylation of intracellular substrates including ZAP-70. To study the potential involvement of tyrosine phosphorylation in CD4+CD8+ [double-positive (DP)] thymocytes in the positive selection process in vivo, we isolated and analyzed them in the presence of phosphatase inhibitor. DP thymocytes were obtained from TCR transgenic mice (TCR-Tg) expressing MHC class I- or class II-restricted TCR in selecting and non-selecting MHC backgrounds respectively. The phosphorylation of ZAP-70 in DP thymocytes of class I-restricted TCR-Tg was significantly higher in the positively selecting background than in the non-selecting one. However, such a phosphorylation difference between selecting and non-selecting TCR-Tg was found to be considerably less in class II-restricted TCR-Tg. A similar bias for ZAP-70 phosphorylation was also observed on selecting DP thymocytes when I-A(beta) deficient- and beta2-microglobulin-deficient mice were compared. These ex vivo studies suggest that TCR-mediated signaling on DP thymocytes induces ZAP-70 phosphorylation under a different manner of engagement of TCR to class I and class II molecules in the positive selection process.

Evidence for down-regulation of highly expressed TCR by CD4 and CD45 on non-selected CD4+CD8+ thymocytes

Immature CD4+CD8+ double-positive (DP) thymocytes are positively selected for further development if they express TCR reacting with thymic ligands of low affinity. However, the majority of DP thymocytes express low TCR levels. This low level of TCR may be insufficient to recognize thymic ligands. To understand the basis for the low expression of TCR on DP thymocytes, we determined the density of TCR expression at various stages of their development using TCR transgenic (TCR-Tg) mice. We found that TCR expression was high in the thymocytes that had recently transited into the DP stage but then gradually decreased on DP cells if they were not selected by TCR interaction with MHC molecules. However, such TCR suppression was not observed in positively selected DP cells and in the non-selected DP cells obtained from CD45 deficient mice or from mice receiving anti-CD4 mAb. These findings suggest that the once highly expressed TCR at the DP stage is suppressed by CD45 and/or CD4 on non-selected thymocytes. Furthermore, TCR suppression is prevented by TCR-mediated signals. The maintenance of high TCR levels on positively selected DP thymocytes may facilitate their selection.

[Thymic lymphoid hyperplasia of myasthenia gravis patients: correlation with clinical features and efficacy of thymectomy]

Thirty nine thymus tissues from myasthenia gravis patients without thymoma who underwent extended thymectomy were evaluated on thymic lymphoid hyperplasia with special emphasis on clinical features and the efficacy of thymectomy. Of 39 patients, 31 were women, but 3 of 7 patients without thymic lymphoid hyperplasia were men. The hyperplastic index of the thymus correlated largely with serum anti-Ach-R antibody titers before surgery. Age, myasthenic type and preoperative duration of the symptoms were almost unrelated to the hyperplastic change in the thymus. The effect of thymectomy was more remarkable in the patients with the hyperplastic thymus than that in them without it, who obtained still no remission after surgery, although the remission rate of them with it reached to 25%. Of 7 patients without the hyperplastic thymus, 4 had no detectable antibody to acetylcholine receptor, whereas in 32 patients with it only 2 were seronegative. This negative immunological factor might make adverse response to thymectomy. Although unfavorable response to thymectomy were observed in the patients without the hyperplastic thymus, most of them were significantly improved through a supplementary treatment with steroid after surgery. Thymectomy was a favorable treatment for myasthenia gravis patients with thymic lymphoid hyperplasia, whereas in them without it the result of thymectomy was unsatisfactory.

[Immediate breast reconstruction with the transverse rectus abdominis musculocutaneous flap (TRAM-flap)]

The surgical treatment of breast cancer shows a recent trend toward breast-saving procedures, in consideration of quality and body image. Surgeons who performed mastectomy, however, have not taken aggressive approaches to reconstructive surgery, leaving this to plastic surgeons. We adopted the transverse rectus abdominis musculocutaneous flap (TRAM-flap) for breast reconstruction in 1988 and performed immediate breast reconstructions in 37 cases. There were no major complications, and good cosmetic results were obtained. For general surgeons, this excellent technique can safely cope with tissue defects in radical mastectomy, as well as modified radical mastectomy. Immediate breast reconstruction with this technique will be an integral part of breast cancer surgery in company with breast-saving surgery.

[B cell population and its autoimmune activity in the thymus of patients associated with myasthenia gravis]

Immunohistochemical studies using antibodies to B lymphocyte and to immunoglobulin G bearing cell were carried out for resected thymus-specimens of 10 patients associated with myasthenia gravis. In each case, abundant B cells (L26 positive cell) resided in the follicles and the medulla of thymus, especially, were congregated in the follicles developing germinal center and around Hassall's corpuscles. Amount of B cell population was various among each case regardless of type of myasthenia gravis or age. B cells were greatly increased in the thymus of patients with values of anti-acetylcholine receptor antibody titers over 100 nmol/l. Although numerous B cells were present in the thymus of these patients, IgG bearing cells were extremely rare. In the most cases, B cells lacked IgG expression. From the results, numerous B cells pre-activating autoimmune antibody production were accumulated in the thymus of patients associated with myasthenia gravis.

[Reoperation in patients with thymoma]

For past seven years, reoperations were carried out for six patients with thymoma and myasthenia gravis (MG). Of six patients, five patients were suspected recurrent thymoma and remaining one patient was diagnosed as the residual thymus after thymothymectomy or thymomectomy. Myasthenia gravis has been progressing in five patients after initial operation except for one patient. Two cases of pleural dissemination tumors, one case of local recurrent thymoma and one case of the residual thymus were confirmed by surgery, remaining two patients had no recurrent tumor. As surgical procedure, median sternotomy using for reoperation has a great surgical risk, because left brachiocephalic vein closely adhered to the sternum is apt to be injured. Clinical symptoms of MG were improved in all the patients after reoperation regardless of recurrent tumor.