| Induction of differentiation and/or apoptosis is a new and promising approach to cancer therapy, well illustrated by the treatment of acute promyelocytic leukaemia (AMPL) with all-trans-retinoic acid (ATRA). Treatment with ATRA results in complete remission in 92-95% of patients with the disease. HL-60 cells have been reported to undergo differentiation in response to RA similar to that observed with primary APML cells, and may be a valid model for this type of leukaemia. It has been shown that retinoic acid (RA) can regulate the expression of multiple genes and consequently plays an important role in physiological and pharmacological functions. To study the mechanism of RA action, previously described changes in gene expression induced by RA had been studied by various methods in past years, such as RT-PCR, differential mRNA display or cDNA microarray. However, the presence of transcripts encoding given proteins could not represent the appearance of corresponding functional protein. Moreover, many proteins induced by RA are not fully characterized and the signalling pathways that regulate their expression are not fully elucidated. RA has been shown to be effective in the therapy of APML and this is assumed to due to differentiation and clonal depletion. For the possible immunological mechanism involved, it was shown that treatment of HL-60 cells with 10 nmol/L RA for 7 days induced them to differentiate into a population that possessed an enhanced immunostimulatory capacity and appeared to be up-regulation of adhesion and costimulatory cell surface molecules. As a clinical drug for cancer differentiation therapy, besides up-regulation of adhesion and costimulatory molecules, the action mechanism of RA is whether it is involved with the expression of some cell proteins. Recently proteomics has been one of hotspots in biological science. Proteome indicates the PROTEins expressed by a genOME or tissue. Unlike the genome, the proteome is not a fixed feature of an organism. Instead, it changes with thestate of development, the tissue or even the environmental condition under which an organism finds itself. The proteomic approach had been applied in multiple areas such as regulation of cell growth and development, signal transduction, molecular marker for disease diagnosis, and pharmaceutical studies, et al. It has been an important part of functional genomics. To understand the action mechanism of RA it is useful to analysis the alteration of protein expression in HL-60 cells treated by ATRA We compared the protein expression profiles in HL-60 cells with and without ATRA treatment by comparative proteome and identified part of protein spots remarkably expressed in treated cells by protein sequencing and database searching.To obtain more differentiated and viable cells, ATRA concentration and treatment time was investigated. The treated cells were monitored by nitro blue tetrazolium (NBT) reduction experiment to indicate cell differentiation and haemocytometric counts using exclusion of trypan blue to indicate cell viability respectively. By comparing different ATRA concentration and treatment time, the concentration of 2×10-7 mol/L ATRA and treatment time of 96 hours were applied. Then the morphology, cell cycles, and immunostimulated capacity of HL-60 cells were tested after 96 hours treatment with ATRA. It was shown that the NBT positive cell is up 90%, part of cells had pseudopod-like projections and kidney-like nuclei, cytoplasmic/nuclear area raio become larger, which it indicated that the treated cells were differentiated along mature pathway. The treated cells were dominant at G0/G1 phase. The increase in cytotoxic activity of responding lymphocytes stimulated with differentiated cells indicated the treated cells with ATRA acquired immunostimulatory capability.To characterize the alteration of protein expression during tumour cell differentiation induced by all-trans retinoic acid (ATRA) and to understand downstream signaling and molecular mechanism of ATRA action, we compared the protein expr...
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