Our results further clarify the mechanism of cisplatin resistance in LCSCs in terms of reduced cisplatin uptake and enhanced ability to implement DNA repairs. These findings may aid in the design of the next-generation of platinum-based anticancer drugs.
We have raised a murine IgM monoclonal antibody (MA6) against immunoprecipitate obtained by reacting the serum of an NPC patient with extract of the Burkitt lymphoma cell line, Raji. It reacts against an antigen (BLCa) which is broadly represented on human B lymphoid tissues and cell lines but is different from the functional B-cell markers such as surface immunoglobulins, Ia products, Fc and complement receptors. BLCa was found to occur on lymphoid cell lines representing all stages of B-cell differentiation. These included the pre-B and null-cell lines, Nalm 6 and Reh, the EBV-transformed lymphoid cell lines and the myeloma cell line. MA6 was reactive against all the Burkitt lymphoma cell lines, whether or not these harbored the EBV genomes, with the exception of P3HR-I. The antibody was found to be selectively reactive against a proportion of peripheral blood B lymphocytes and to stain the B-cell-rich primary follicles and mantle zones of secondary follicles in the lymph node. However, MA6 was not reactive against cell lines of T-lymphocyte, myeloid, monocyte fibroblast or epithelial origin. It did, nevertheless selectively stain tumor cells from a variety of carcinoma tissues originating from different anatomical sites, including the nasopharynx.
The murine monoclonal antibody (MAb) MA6 is selectively reactive against a large variety of human B lymphocytes including those in early stages of B-cell differentiation such as committed progenitors of B lymphocytes, pre-B lymphocytes, Burkitt lymphoma cells, and those at later stages of differentiation such as peripheral blood B lymphocytes and myeloma cells. The major antigen identified by this antibody on such B lymphocytes (BLCa) is a 55-kDa glycoprotein or a group of similar glycoproteins, with the MA6-reactive determinant localized on the carbohydrate moiety. On isoelectric focusing, this antigen exhibits a degree of charge microheterogeneity, migrating as a diffused band with an average isoelectric point at pH 5.7. BLCa was also identified by another murine MAb, MA5. The antigenic determinant recognized by this antibody is also localized on the carbohydrate moiety of the molecule, but, unlike the MA6-reactive determinant, it is shared by other glycoproteins from different types of cells.
An electroporation device was developed to introduce transient membrane pores and, consequently, enhance membrane permeability in living cells in a controllable manner. The validity of this platform was assessed on six non-small cell lung cancer (NSCLC) cell lines using different fluorescent dyes. Interestingly, it was found that the electroporation efficiency of these cells, i.e. the percentage of cells with membrane pores created, decreases significantly (from ∼60% to 30%) as their resistivity against Erlotinib increases, demonstrating the potential of such approach as a screening tool for assessing drug resistance in tumours in the future. Furthermore, we showed that the inverse relationship between the electroporation efficiency and Erlotinib resistance is likely due to the fact that NSCLC cell lines with higher drug resistivity appear to have lower cortical tensions and hence make it harder for membrane pores to be created, consistent with existing electroporation theories.
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