Proteasomes are the main proteases responsible for cytosolic protein degradation and the production of major histocompatibility complex class I ligands. Incorporation of the interferon γ–inducible subunits low molecular weight protein (LMP)-2, LMP-7, and multicatalytic endopeptidase complex–like (MECL)-1 leads to the formation of immunoproteasomes which have been associated with more efficient class I antigen processing. Although differences in cleavage specificities of constitutive and immunoproteasomes have been observed frequently, cleavage motifs have not been described previously.We now report that cells expressing immunoproteasomes display a different peptide repertoire changing the overall cytotoxic T cell–specificity as indicated by the observation that LMP-7−/− mice react against cells of LMP-7 wild-type mice. Moreover, using the 436 amino acid protein enolase-1 as an unmodified model substrate in combination with a quantitative approach, we analyzed a large collection of peptides generated by either set of proteasomes. Inspection of the amino acids flanking proteasomal cleavage sites allowed the description of two different cleavage motifs. These motifs finally explain recent findings describing differential processing of epitopes by constitutive and immunoproteasomes and are important to the understanding of peripheral T cell tolerization/activation as well as for effective vaccine development.

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BACKGROUND Extraadrenal paragangliomas of the head and neck are tumors with variable clinical behavior. Because tumor growth as well as surgery can cause disabling loss of function, knowledge of the natural history of paragangliomas is important for the development of treatment strategies. METHODS The tumor volume, growth rate, and tumor doubling time of 48 paragangliomas at different anatomic locations in the head and neck region were estimated retrospectively using sequential radiologic imaging. RESULTS During a mean follow‐up period of 4.2 years, a volume increase of > 20% was observed in 60% of the paragangliomas. In these cases the median growth rate was 1.0 mm/year and the median tumor doubling time was 4.2 years. More growing tumors were observed in intermediate size tumors than in very small or large paragangliomas, suggesting a biphasic growth pattern. CONCLUSIONS The majority of head and neck paragangliomas have a very low growth rate. Although management of paragangliomas also is determined by other parameters, preoperative estimation of the tumor doubling time may influence the treatment proposal. A “wait and scan” policy must be considered in all cases. Cancer 2000;88:2811–6. © 2000 American Cancer Society.

The incidence and the severity of chemotherapy-associated oral mucositis were determined in a retrospective analysis of 150 patients with various solid tumors. In addition, possible risk factors for the development of mucositis were identified. Patients were treated with chemotherapeutic regimens appropriate to tumor type and disease stage on an in- or outpatient basis. Mucositis was scored using the World Health Organization (WHO) criteria. Eighty-seven episodes of mucositis occurred in 47 (31%) patients. Twenty-six patients each experienced only one episode, whereas 21 patients had up to eight episodes of mucositis. The 1,281 chemotherapy cycles that have been analyzed included 87 cycles in which mucositis was observed. In 16 patients (11%) only slight oral mucosal changes were recorded (maximum WHO score 1), while 25 patients (17%) experienced mild to moderate mucositis (maximum WHO score 2), and in 6 patients (4%) mucositis was moderate to severe (maximum WHO score 3). No grade 4 mucositis developed. In 24 of the 47 patients with mucositis (51%) clinical features of acute pseudomembranous candidiasis were present. Leukopenia, leukopenic fever, and use of corticosteroids and central venous catheters were associated with the chemotherapy cycles with mucositis. Multivariate analysis identified the administration of paclitaxel, doxorubicin, or etoposide as independent risk factor (adjusted rate ratios 8.06, 7.35, and 6.70, respectively), whereas low body mass was associated with a slightly increased risk (adjusted rate ratio 0.92) for the development of mucositis. In conclusion, almost one-third of patients receiving chemotherapy for solid tumors experienced one or more episodes of mild to more severe oral mucositis, indicating that this is a frequent complication in such patients.