Chromatin condensation and DNA cleavage at internucleosomal sites have been recognized early as hallmarks of apoptosis, and it has been suggested that extensive DNA chain scission could directly result in the formation of dense chromatin bodies. Here we have shown that no causal relationship exists between DNA degradation and chromatin condensation in glucocorticoid-induced thymocyte apoptosis. The chromatin rearrangement occurred independent of as well as prior to DNA cleavage and involved a specific conformational change at the nucleosome level. In the early stages of the process, the core particles appeared to be tightly packed face-to-face in smooth 11-nm filaments that progressively folded to generate a closely woven network. The network finally collapsed, producing dense apoptotic bodies. Since trypsin digestion relaxed condensed chromatin and histone H4 underwent appreciable deacetylation in the apoptotic cell, we suggest that changes in the DNA-histone interactions represented a major modulating factor of condensation.Although the term "apoptosis" was originally derived from the Greek to emphasize cytoplasmic and nuclear alterations peculiar to the process of programmed cell death (1), no attempt has been made thus far to search for the molecular events underlying these changes, particularly the collapse of the bulk of chromatin into dense domains. The reasons for this delay in the development of a fundamental approach are manifold. In the first place, the unique condensed appearance of the apoptotic nucleus is closely associated with the cleavage of chromatin at internucleosomal sites (2), a circumstance that supports the hypothesis of a causal relationship between extensive chromatin digestion and condensation (3). This early view has recently been challenged on the basis of more refined determinations of the chain length of the DNA isolated from apoptotic cells (4 -6) but has long distracted from the search for the molecular mechanisms involved in the process of condensation. Moreover, since apoptosis plays a key regulatory role in several physiological and pathological processes, major efforts are currently being directed to the elucidation of the biochemical aspects and to the identification of the genes involved in the activation of the cell death program. The onset of chromatin condensation might direct the orderly turning off of genes required for the execution of metabolic suicide, therefore warranting a detailed structural characterization of apoptotic chromatin and a search for terminal modulating factors.Bearing in mind the spatial distribution of interphase chromatin, the appearance of the apoptotic nucleus immediately suggests the occurrence of a structural change involving extremely large domains, and the question arises whether a specific conformational transition at the nucleosome level might account for such a catastrophic phenomenon. In the first place, is chromatin in apoptosis characterized by a three-dimensional array of nucleosomes different from that prevailing in the interphase 3...

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Rationale: Loss of histone macroH2A1 induces appearance of cancer stem cells (CSCs)-like cells in hepatocellular carcinoma (HCC). How CSCs interact with the tumor microenvironment and the adaptive immune system is unclear.Methods: We screened aggressive human HCC for macroH2A1 and CD44 CSC marker expression. We also knocked down (KD) macroH2A1 in HCC cells, and performed integrated transcriptomic and secretomic analyses.Results: Human HCC showed low macroH2A1 and high CD44 expression compared to control tissues. MacroH2A1 KD CSC-like cells transferred paracrinally their chemoresistant properties to parental HCC cells. MacroH2A1 KD conditioned media transcriptionally reprogrammed parental HCC cells activated regulatory CD4+/CD25+/FoxP3+ T cells (Tregs).Conclusions: Loss of macroH2A1 in HCC cells drives cancer stem-cell propagation and evasion from immune surveillance.

INTRODUCTIONMetastases to the breast from extra-mammary tumors are uncommon and few sporadic cases are reported in the international literature. An accurate differential diagnosis of secondary cancer is mandatory because both prognosis and treatment differ with respect to primary breast tumors.PRESENTATION OF CASEWe present the case of a 70-year-old woman with an isolated metastasis to the breast occuring 9 years after undergoing a nephrectomy for Renal Cell Carcinoma (RCC).Clinical examination revealed a palpable and mobile mass in the right breast with an enlarged ipsilateral axillary lymph node. Mammographic findings showed a dense, well circumscribed solid mass and the breast ultrasonography findings were those of a hypoechoic homogeneous solid nodule with no posterior attenuation but with prominent peripheral vascularity. A tru-cut biopsy was conclusive for a metastatic deposit by RCC. A whole-body CT scan showed no evidence of further recurrences. The patient underwent metastasectomy and exeresis of the papable lymphnode.DISCUSSIONIn patients with former surgery for RCC, a diagnosis based on a preoperative biopsy allows to indicate the proper surgical treatment: in facts, as compared to primary breast tumors treatment, the rationale to pursue wide surgical margins is pointless in cases of metastases and, similarly, the biopsy of the sentinel lymphnode is void of sense due to the lack of its physiopathological prerequisite.CONCLUSIONWe suggest to consider a micro-histological biopsy of any new breast lesion appearing in a patient with a history of treatment for RCC. Prompt diagnosis is necessary to choose the right treatment.

Many catalases have the shared property of containing bound NADPH and being susceptible to inactivation by their own substrate, H2O2. The presence of additional (unbound) NADPH effectively prevents bovine liver and human erythrocytic catalase from becoming compound II, the reversibly inactivated state of catalase, and NADP+ is known to be generated in the process. The function of the bound NADPH, which is tightly bound in bovine liver catalase, has been unknown. The present study with bovine liver catalase and [14C]NADPH and [14C]NADH revealed that unbound NADPH or NADH are substrates for an internal reductase and transhydrogenase reaction respectively; the unbound NADPH or NADH cause tightly bound NADP+ to become NADPH without becoming tightly bound themselves. This and other results provide insight into the function of tightly bound NADPH.