The tumor necrosis factor (TNF), Fas, and TNF-related apoptosis-inducing ligand (TRAIL) receptors (R) are highly specific physiological mediators of apoptotic signaling. We observed earlier that a number of FasR-insensitive cell lines could redirect the proapoptotic signal to an anti-apoptotic ERK1/2 signal resulting in inhibition of caspase activation. Here we determine that similar mechanisms are operational in regulating the apoptotic signaling of other death receptors. Activation of the FasR, TNF-R1, and TRAIL-R, respectively, rapidly induced subsequent ERK1/2 activation, an event independent from caspase activity. Whereas inhibition of the death receptor-mediated ERK1/2 activation was sufficient to sensitize the cells to apoptotic signaling from FasR and TRAIL-R, cells were still protected from apoptotic TNF-R1 signaling. The latter seemed to be due to the strong activation of the anti-apoptotic factor NF-B, which remained inactive in FasR or TRAIL-R signaling. However, when the cells were sensitized with cycloheximide, which is sufficient to sensitize the cells also to apoptosis by TNF-R1 stimulation, we noticed that adenovirus-mediated expression of constitutively active MKK1 could rescue the cells from apoptosis induced by the respective receptors by preventing caspase-8 activation. Taken together, our results show that ERK1/2 has a dominant protecting effect over apoptotic signaling from the death receptors. This protection, which is independent of newly synthesized proteins, acts in all cases by suppressing activation of the caspase effector machinery.

Controlled degradation of extracellular matrix (ECM) is essential for the growth, invasion, and metastasis of malignant tumors, and for tumor-induced angiogenesis. Matrix metalloproteinases (MMPs) are a family of zinc-dependent neutral endopeptidases collectively capable of degrading essentially all ECM components and they apparently play an important role in all these aspects of tumor development. Furthermore, recent evidence suggests that MMPs also play a role in tumor cell survival. In this review, we discuss the current concept concerning the role of MMPs and their inhibitors in tumor invasion, as a basis for prognosis and targeted therapeutic intervention in cancer.

Tissue inhibitors of metalloproteinases (TIMPs) are important regulators of matrix metalloproteinase (MMP) and adamalysin (ADAM) activity. We have previously shown that adenovirally expressed tissue inhibitor of metalloproteinases-3 (TIMP-3) induces apoptosis in melanoma cells and inhibits growth of human melanoma xenografts. Here, we have studied the role of death receptors in apoptosis of melanoma cells induced by TIMP-3. Our results show, that the exposure of three metastatic melanoma cell lines (A2058, SK-Mel-5, and WM-266-4) to recombinant TIMP-3, N-terminal MMP inhibitory domain of TIMP-3, as well as to adenovirally expressed TIMP-3 results in stabilization of tumor necrosis factor receptor-1 (TNF-RI), FAS, and TNFrelated apoptosis inducing ligand receptor-1 (TRAIL-RI) on melanoma cell surface and sensitizes these cells to apoptosis induced by TNF-a, anti-Fas-antibody and TRAIL. Stabilization of death receptors by TIMP-3 results in activation of caspase-8 and caspase-3, and subsequent apoptosis is blocked by specific caspase-8 inhibitor (Z-IETD-FMK) and by pan-caspase inhibitor (Z-DEVD-FMK). Adenovirus-mediated expression of TIMP-3 in human melanoma xenografts in vivo resulted in increased immunostaining for TNF-RI, FAS, and cleaved caspase-3, and in apoptosis of melanoma cells. Taken together, these results show that TIMP-3 promotes apoptosis in melanoma cells through stabilization of three distinct death receptors and activation of their apoptotic signaling cascade through caspase-8.

Here, we have examined the role of distinct MAPK pathways in the regulation of collagenase-1 (matrix metalloproteinase (MMP)-1) and stromelysin-1 (MMP-3) expression by human skin fibroblasts. Tumor necrosis factor-␣ rapidly and transiently activated ERK1/2 and JNK in fibroblasts, whereas the activation of p38 MAPK was more persistent. Inhibition of p38 activity by SB203580 markedly (by 80 -90%) inhibited induction of MMP-1 and MMP-3 expression by tumor necrosis factor-␣, whereas blocking the activation of ERK1/2 by PD98059 had no effect. Activation of endogenous ERK1/2 by adenovirusmediated transfer of constitutively active MEK1 resulted in potent induction of MMP-1 and MMP-3 expression. Activation of endogenous or adenovirally expressed p38␣ by adenovirally delivered constitutively active MKK3b and MKK6b also enhanced MMP-1 and MMP-3 expression and augmented the up-regulatory effect of ERK1/2 activation on the expression of these MMPs. Activation of ERK1/2 resulted in induction of c-jun, junB, and c-fos expression, whereas activation of p38 alone had no effect. In contrast, activation of p38␣ resulted in marked stabilization of MMP-1 and MMP-3 mRNAs. These results identify two distinct and complementary signaling mechanisms mediating induction of MMP-1 and MMP-3 expression in dermal fibroblasts: AP-1-dependent transcriptional activation via the ERK1/2 pathway and AP-1-independent enhancement via p38␣ MAPK by mRNA stabilization. It is conceivable that both modes of action play an important role in controlling the proteolytic phenotype of fibroblasts, e.g. in wound repair and tumor invasion.

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We have studied the effect of a newly identified tumor suppressor tissue inhibitor of metalloproteinases- 3 (TIMP-3) on the growth of human melanoma and squamous-cell carcinoma (SCC). Adenoviral delivery of the TIMP-3 gene to human melanoma (A2058) and SCC (UT-SCC-7) cells ex vivo inhibited tumorigenesis after subcutaneous (s.c.) injection of the infected cells into SCID/SCID mice. Three daily consecutive intratumoral injections of 1.4x10(9) plaque-forming units (pfu) of TIMP-3 adenovirus (RAdTIMP-3) inhibited the growth of preestablished melanoma and SCC xenografts in SCID/SCID mice, whereas growth of control virus-injected tumors was not affected. The antitumor effect of RAdTIMP-3 was obtained with in vivo adenoviral transduction efficiency of 8-10%, and it was more potent than that of adenovirally delivered p53. Adenovirusmediated expression of TIMP-3 potently reduced gelatinolytic activity, increased the number of apoptotic cells, and inhibited vascularization of melanomas. Escalation of the adenoviral dose to three rounds of three daily consecutive injections with 1.4x10(9) pfu of RAdTIMP-3 every 6 days entirely inhibited growth of injected melanomas for 32 days. Mixing RAdTIMP-3-infected A2058 cells with uninfected cells in 1:1 ratio in culture resulted in death of all cells in 96 hours. Adenovirally delivered TIMP-3 was also expressed by A2058 cells in soluble form into the culture medium, where it exerted a cytotoxic effect on uninfected A2058 cell cultures after relocating to the cell layer. These results identify TIMP-3 as a novel type of secreted tumor suppressor, which has antiinvasive, antiangiogenic, and proapoptotic effects in vivo, and which displays a potent bystander effect validating further exploration of its applicability in human cancer gene therapy.

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Background and Aims: The coronavirus outbreak significantly changed the need of healthcare services. We hypothesized that the COVID-19 pandemic decreased the frequency of pediatric fracture operations. We also hypothesized that the frequency of emergency pediatric surgical operations decreased as well, as a result of patient-related reasons, such as neglecting or underestimating the symptoms, to avoid hospital admission. Materials and Methods: Nationwide data were individually collected and analyzed in all five tertiary pediatric surgical/trauma centers in Finland. Operations related to fractures, appendicitis, and acute scrotum in children aged above 16 years between March 1 and May 31 from 2017 to 2020 were identified. The monthly frequencies of operations and type of traumas were compared between prepandemic 3 years and 2020. Results: Altogether, 1755 patients were identified in five tertiary hospitals who had an emergency operation during the investigation period. There was a significant decrease (31%, p = 0.03) in trauma operations. It was mostly due to reduction in lower limb trauma operations (32%, p = 0.006). Daycare, school, and organized sports–related injuries decreased significantly during the pandemic. These reductions were observed in March and in April. The frequencies of appendectomies and scrotal explorations remained constant. Conclusion: According to the postulation, a great decrease in the need of trauma operations was observed during the peak of COVID-19 pandemic. In the future, in case similar public restrictions are ordered, the spared resources could be deployed to other clinical areas. However, the need of pediatric surgical emergencies held stable during the COVID-19 restrictions.