No abstract

Summary HuIL-6 cDNA, cloned into a neomycin resistant conferring expression vector, BMGNeo, was transfected into Lewis Lung Carcinoma (LLC) cells. LLC cells (5 x 106 ml-X) transfected with IL-6 cDNA (LLC-IL6) secreted IL-6 into the culture supernatant at a concentration of 9.9 ngml-' within 48 h. When 1,000,000 of untransfected LLC, BMGNeo vector transfected LLC (LLC-Neo) or LLC-1L6 cells were transplanted into C57BL/6 mice subcutaneously, the mean ± s.d. of survival times of these mice were 33.3 ± 9.7, 34.3 ± 7.1 and 17.0 ± 3.1 days, respectively. The survival time of LLC-1L6 cells transplanted mice was significantly shorter than that of LLC (P<0.01) or LLC-Neo (P<0.01) cells transplanted mice without a measurable difference of tumour size. Plasma concentration of IL-6 steadily increased in LLC-IL6 transplanted mice. Body weight and serum albumin were significantly lower in LLC-1L6 transplanted mice than in LLC transplanted mice. Mouse IL-la and mouse TNF-a were not detected in the plasma of LLC-1L6 transplanted mice. These data suggested that secretion of IL-6 from LLC cells was unable to alter net tumour growth rate but rather caused a state similar to cachexia without detectable increase of IL-Ia and TNF-a in the plasma. This state may be responsible for the shortened survival of LLC-1L6 tumour-bearing mice.

Eukaryotic structural maintenance of chromosome proteins (SMC) are major components of cohesin and condensins that regulate chromosome structure and dynamics during cell cycle. We here determine the crystal structure of human condensin SMC hinge heterodimer with ϳ30 residues of coiled coils. The structure, in conjunction with the hydrogen exchange mass spectrometry analyses, revealed the structural basis for the specific heterodimer formation of eukaryotic SMC and that the coiled coils from two different hinges protrude in the same direction, providing a unique binding surface conducive for binding to single-stranded DNA. The characteristic hydrogen exchange profiles of peptides constituted regions especially across the hinge-hinge dimerization interface, further suggesting the structural alterations upon single-stranded DNA binding and the presence of a half-opened state of hinge heterodimer. This structural change potentially relates to the DNA loading mechanism of SMC, in which the hinge domain functions as an entrance gate as previously proposed for cohesin. Our results, however, indicated that this is not the case for condensins based on the fact that the coiled coils are still interacting with each other, even when DNA binding induces structural changes in the hinge region, suggesting the functional differences of SMC hinge domain between condensins and cohesin in DNA recognition.

In order to develop a more effective method of immunotherapy we have transfected mouse interleukin-2 (IL2) or mouse interleukin-4 (IL4) cDNA into a spontaneous non-immunogenic murine lung cancer. Lewis lung carcinoma (LLC). IL2 cDNA transfection more strongly decreases tumorigenicity of LLC than IL4 cDNA transfection. Recombinant-human-IL2 treatment of mice that were transplanted with untransfected LLC could not prolong their survival. In contrast, vaccination with IL2-cDNA-transfected LLC (LLC-IL2) and LLC-IL2 mixed with IL4-cDNA-transfected LLC (LLC-IL4) could significantly suppress tumor growth of LLC in a tumor-specific manner. The vaccination with LLC-IL2 mixed with the same number of LLC-IL4 cells was more suppressive to the growth of LLC than that with LLC-IL2 cells alone, while LLC-IL4 vaccination alone was ineffective. Nude, severe-combined-immune-deficient (SCID) and beige mice were unable to reject LLC-IL2 cells. However, immunodeficient mice responded to LLC-IL2, but not to LLC, since their survival times after transplantation with LLC-IL2 cells were significantly longer than the survival time of normal or immunodeficient mice transplanted with untransfected LLC cells. We conclude that vaccination with IL2-producing tumors and, with more pronounced effect, in combination with IL4-producing tumors, is able to induce an immune response to this normally non-immunogenic tumor. Tumor rejection appears to be achieved by the combined activity of CTL and NK cells. This strategy has potential for new immunotherapeutic interventions in cancer patients.

We oxidized histidine residues in monoclonal antibody drugs of immunoglobulin gamma 1 (IgG1) using ultraviolet C irradiation (UVC: 200-280 nm), which is known to be potent for sterilization or disinfection. Among the reaction products, we identified asparagine and aspartic acid by mass spectrometry. In the photo-induced oxidation of histidine in angiotensin II, 18 O atoms from H 2 18 O in the solvent were incorporated only into aspartic acid but not into asparagine. This suggests that UVC irradiation generates singlet oxygen and induces [2 + 2] cycloaddition to form a dioxetane involving the imidazole c γ − C δ2 bond of histidine, followed by ring-opening in the manner of further photo-induced retro [2 + 2] cycloaddition. This yields an equilibrium mixture of two keto-imines, which can be the precursors to aspartic acid and asparagine. The photo-oxidation appears to occur preferentially for histidine residues with lower pK a values in IgG1. We thus conclude that the damage due to UVC photo-oxidation of histidine residues can be avoided in acidic conditions where the imidazole ring is protonated.