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Lectin reactivity of murine fibrosarcoma lines with a different metastatic potential.

Lectins are suitable tools for investigating the glycoconjugate characteristics of metastatic cells. In the present study, we investigated whether there were differences between high metastatic T3 cells and a low metastatic isolate in their reactivities to several lectins specific for galactosyl and sialyl groups. Analysis of reactivity of the two cell lines to wheat germ agglutinin revealed a complex pattern. In fact, T3 cells had high-affinity, neuraminidase-resistant as well as low-affinity, neuraminidase-sensitive receptors. Instead, the low metastatic isolate showed only high-affinity receptors, both neuraminidase-resistant and neuraminidase-sensitive The two cell lines reacted similarly to galactose-specific lectins. These findings indicate that sialyl groups, rather than galactosyl groups, affect the metastatic behavior of our cell system.

Animals↗

Improved response of a murine fibrosarcoma (Meth-A) to interstitial radiation when combined with hyperthermia.

Removable Iridium-192 implants provided a dose of 10 Gy/day or 41.5 cGy/hr at 0.5 cm from the center of 1.0 cm diameter tumors. The total radiation (x) alone was 20, 40 or 60 Gy, representing 2, 4, or 6 days of continuous radiation. The doses used for the combined treatments at elevated temperatures were 10, 20 or 30 Gy. The local tumor hyperthermia (LTH) treatment (43.6 for 35 min, water bath) was administered once for each 10 Gy of dose. The combined radiation + LTH was clearly superior to that achieved with radiation or LTH alone and yielded Thermal Enhancement Ratios (TER) of 3.4-3.9. Local tumor control rate was 67% and 89% for the 20 and 30 Gy x + LTH groups, respectively. A comparison of the results obtained in this study with those of earlier studies on the same tumor system indicate that the effects of Iridium-192 alone on this rapidly proliferating tumor were comparable to similar total doses of fractionated external beam radiation. Iridium + LTH produced a tumor response comparable to that achieved with external fractionated radiation + LTH. Combined treatment effect of elevated temperature appears to be less dose rate dependent in the range of 40 cGy/hr to 100 cGy/min and more dependent upon total dose accumulation.

Animals↗

Radioprotection of mouse skin vasculature and the RIF-1 fibrosarcoma by WR-2721.

The degree of radioprotection obtained with WR-2721 is critically dependent upon the oxygen tension of the tissue concerned. It was therefore considered of interest to examine the response of vascular tissue, which would be supposedly well oxygenated, to treatment with WR-2721 plus X rays. The response of this tissue is of interest because of its role in late radiation damage. In addition, for therapeutic gain an agent must protect normal tissue without concomitant tumor protection. However, data on tumor radioprotection have been conflicting and therefore the effect of WR-2721 on an experimental tumor was also tested. Vascular damage was assessed using the fact that tumors grow more slowly in irradiated beds (Tumor Bed Effect). The response of the RIF-1 tumor treated in vivo was measured by in vitro assay of clonogenic survival. WR-2721 (400 mg kg-1) injected 30 minutes before 5 to 30 Gy X rays protected skin stroma by a factor of 1.6. However, WR-2721 given 10 to 60 minutes before 20 Gy X rays to the RIF-1 tumor had either no effect or was protective, according to the method of immobilizing the mice during irradiation. Differences between the ways animals are physically restrained for tumor irradiation could account for the conflicting data concerning tumor radioprotection with WR-2721.

Amifostine↗

Reduction of invasion in human fibrosarcoma cells by ribosomal protein S3 in conjunction with Nm23-H1 and ERK.

RpS3 is a component of the 40S ribosomal subunit of eukaryotes and also plays a role as a base damage endonuclease. Nm23-H1 encodes nucleoside diphosphate kinase A and acts as a suppressor of metastasis in certain human tumors. RpS3 interacted with nm23-H1, and the two proteins were colocalized in the cell periphery and cytoplasm. The 190th leucine of rpS3, and the 118th histidine and the 120th serine of nm23-H1 play key roles in the interaction of two proteins, respectively. The expression of rpS3 reduced the secretion of MMP-9 and the invasive potential in HT1080 cells. Additionally, the phosphorylated ERK was reduced by the expression of rpS3. In MCF7 cells, where the ERK pathway is inactivated and MMPs are not secreted and the ERK pathway can be activated by PMA, the PMA-induced ERK phosphorylation was reduced by the expression of rpS3. However, the L190A mutant of rpS3, which did not interact with nm23-H1, did not inhibit the invasive potential, the secretion of MMP-9, and the activation of the ERK pathway in HT1080 cells and PMA-activated MCF7 cells. These results suggest that rpS3 inhibits invasion via blocking the ERK pathway and MMP-9 secretion; the results also suggest that the interaction of rpS3 and nm23-H1 appears to be critical in this inhibition.

Breast Neoplasms↗

Regulation of collagen prolyl 4-hydroxylase and matrix metalloproteinases in fibrosarcoma cells by hypoxia.

The cellular response to hypoxia is characterized by an enhanced deposition of extracellular matrix (ECM) components, mainly collagens. Collagen homeostasis is determined by the rate of synthesis and degradation. In this study, we investigated the synthesis of enzymes of collagen metabolism like collagen prolyl 4-hydroxylase (P4H), matrix metalloproteinases (MMP-2 and MMP-9) and their regulatory factors MT1-MMP, TIMP-1 and TIMP-2 in HT1080 fibroblasts under the influence of hypoxia. The results indicate that hypoxia affects collagen homeostasis in a biphasic manner concerning basic mechanisms of gene expression. P4H-alpha subunits are up-regulated at the transcriptional and translational level, whereas the beta-subunit is not susceptible to hypoxia. MMP-9 is primarily regulated at the transcriptional and translational level, whereas MMP-2 is mainly controlled by proteolytic activation of the proenzyme. Our results suggest that short-term hypoxia facilitates fibrosis in HT1080 cells by activation of P4H-alpha expression and inhibition of the synthesis of MMPs. Under long-term hypoxia, however, anti-fibrotic mechanisms prevail. Although P4H-alpha expression sustains at a high level, collagenolytic activities dominate by abolishing inhibition of synthesis and activity of MMPs.

Blotting, Western↗

Immunohistochemical study of STAT3 expression in feline injection-site fibrosarcomas.

STAT3 (signal transducer and activator of transcription 3) is a cytoplasmic transcription factor that plays a role in the G1 to S phase cell-cycle transition and is induced by cytokines and growth factors. In the present study, the relation between histological grade and anti-STAT3 immunoreactivity was evaluated in 39 feline injection-site sarcomas treated surgically, 24 of the cats having received preoperative treatment with doxorubicin. Anti-STAT3 immunoreactivity was significantly lower in cases receiving preoperative doxorubicin, specifically with regard to nuclear localization. Moreover, STAT3 expression (intranuclear) was significantly correlated with mitotic activity in the animals that did not receive doxorubicin (P=0.019), and with differentiation score (P=0.009). STAT3 expression was correlated with the histological grade in both doxorubicin-treated and -untreated cats; in the treated cats, however, this correlation applied only to cytoplasmic STAT3 (P=0.018). Doxorubicin treatment induced a significant decrease in STAT3 expression (nuclear, P<0.0001; cytoplasmic, P=0.033) as compared with cases treated by surgery alone. These findings support existing evidence from human and experimental pathology on the potential role of STAT3 in oncogenesis and tumour progression.

Animals↗