Multidrug resistance of non-adherent cancer cells

Metastases are the cause of 90% of human cancer deaths. Cancer in _situ_ can usually be effectively removed by surgery. Once cancer cells disseminate from the original site and start to circulate in blood, lymph, or other body fluids, the disease becomes almost incurable. Here we show that cancer cells in a non-adherent, 3-dimentional growth pattern are highly drug resistant compared to their adherent counterparts that grow in monolayer, attaching to the wall of tissue culture plates. The non-adherent cancer cells retain the adhering potential and can attach to an appropriate surface to reacquire adherent phenotype. Once the non-adherent cancer cells become attached, they regain drug response, similar to the original adherent cells. A significant increase in the expression of CD133, CD44, Nanog, survivin, and thymidylate synthase was observed in the non-adherent cancer cells compared to their adherent counterparts, which may underlie the mechanisms of multidrug resistance of the cells. Since the non-adherent cancer cells cultured in vitro resemble the circulating metastatic cells in vivo in that both cells exhibit suspended non-adherent phenotype, possess re-attaching potential, and are highly drug resistant, we suggest that circulating metastatic cells can attach to an appropriate surface to gain adherent phenotype and subsequently acquire drug sensitivity. We propose that devices coated with cell attachment materials or small particles of extracellular matrix and collagen that mimic the structural framework of real human tissues to which cells can attach and grow may be able to stabilize the circulating metastatic cells. Once the metastatic cells undergo attachment and become adherent, they gain drug sensitivity and can be killed by anticancer drugs that are either administered to the blood or conjugated to the devices

The Distribution of Histone Polypeptides and It\u27s Methylated Basic Amino Acids from the Various Organs of the Rat

Total histones were extracted from the cerebellum, cerebrum, liver, thymus and kidney of thirty 12 day old albino rats. Polyacrylamide gel electrophoresis of twenty-five μg of histone from the various organs was carried out. The F1, F3, F2a2 plus F2b and F2a1 components were separated into distinct bands and the relative percent of the various bands on the gels were determined by scanning the gels through a densitometer. The relative distribution of the histone components from the various organs was compared. It was found that there was no significant difference in the distribution of the histone components from the organs studied. The distribution of the various histone components does not exhibit any form of tissue heterogeneity. The five histone components (F1, F2a2, F2b, and F2a1) from the nuclei of the cerebellum, cerebrum, liver, thymus and lidney of forty-six 15 days old albino rats, which had previously received 10 μcuries of L-[3H] lysine and 5 μcuries of L-[14C-methyl] methionine, were extracted. The animals were sacrificed 14 days after the injection of the isotopic compounds. The various histone components from the various organs were further purified by gel filtration and their purity checked by polyacrylamide gel electrophoresis. The purified histone components were hydrolyzed in 6 N HCl in vacuo and the basic amino acids fractionated on Beckman P-35 resin. Quantitation of the basic amino acids were carried out with the aid of an automatic amino acid analyzer. It was found that only F2a1 and F3 histones were methylated significantly. The products of methylation in the F2a1 histones were ε-N-monomethyllysine and ε-N-dimethyllysine, with a predominance of ε-N-dimethyllysine. The products of the methylation in the F3 histones were ε-N-monomethyllysine, ε-N-dimethyllysine and ε-N-trimethyllysine. No methylarginine was detected in any of the histones analyzed. The amount of methyllysine in the F2a1 histones varied from 0.67 moles/mole in kidney to 0.93 moles/mole in cerebrum. Liver F2a1 had the second highest amount of methyllysine next to cerebrum. The slightly higher methyllysine content in the cerebrum and liver may reflect the maturity of those cells in these particular organs. Since methylation of the lysyl residues occurs after the synthesis of the polypeptide chain, methylation of the histones in newly formed cells might be slightly less in older, matured ells. Pure F3 histones were obtained by repeated gel filtration after which quantities available did not allow for complete analysis. It appears that methylation of the lysyl residues in the histone polypeptides does not contribute to tissue heterogeneity

Modulation of fibronectin synthesis and fibronectin binding during transformation and differentiation of mouse AKR fibroblasts

In previous studies it was shown that transformation of AKR fibroblasts with 3-methylcholanthrene was associated with a loss of surface fibronectin and that induction of differentiation of the transformed cells with N,N-dimethylformamide (DMF) was associated with reacquisition of surface fibronectin (Chakrabarty et al., J. Cell. Physiol. 133:415, 1987). It is shown in the present study that changes in surface fibronectin reflect altered fibronectin synthesis and altered fibronectin binding. Both the nontransformed cells (AKR-2B) and their transformed counterparts (AKR-MCA) bound 125 I-fibronectin in a receptor-like fashion, but the AKR-MCA cells had only 20% of the receptors found on the AKR-2B cells. Whole cell extracts prepared from the AKR-2B cells and separated by sodium dodecyl sufate-polyacrylamide gel electrophoresis under reducing conditions were examined for 125 I-fibronectin binding. Under these conditions, the majority of binding occurred to moieties with molecular weights of 180 kD, 150 kD, and 97 kD. Binding to similar moieties on the AKR-MCA cells was virtually absent but occurred rapidly after treatment with DMF. The appearance of these moieties paralleled the acquisition of 125 I-fibronectin binding activity by whole cells. Antibodies to the fibronectin receptor isolated from human placenta reacted with the DMF-sensitive moieties in immunoblot assays. Both the appearance of the fibronectin binding moieties and the acquisition of 125 I-fibronectin binding activity by whole cells occurred within 6 hr of DMF treatment and increased over the suosequent 4 day period. The time course of these events paralleled closely the time course for induction of fibronectin biosynthesis by DMF. These changes in fibronectin binding and fibronectin production were associated with alterations in cell-substrate adhesion. The AKR-2B cells rapidly attached and spread on bovine serum albumin-coated dishes and on fibronectin-coated dishes, whereas the AKR-MCA cells were less adhesive on both substrates. Capacity to attach and spread was regained concomitantly with the induction of fibronectin binding and fibronectin production. Adhesion on both substrates was partially inhibited by antibodies to the fibronectin receptor and by RGDS. These studies suggest that fibronectin production and fibronectin binding are coregulated in AKR fibroblasts and that they function together to bring about changes in cell-substrate adhesion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49878/1/1041430307_ftp.pd

Induction of calcium sensing receptor in human colon cancer cells by calcium, vitamin D and aquamin: Promotion of a more differentiated, less malignant and indolent phenotype

The calcium sensing receptor (CaSR) is a robust promoter of differentiation in colonic epithelial cells and functions as a tumor suppressor. Cancer cells that do not express CaSR (termed CaSR null) are highly malignant while acquisition of CaSR expression in these cells circumvents the malignant phenotype. We hypothesize that chemopreventive agents mediate their action through the induction of CaSR. Here, we compare the effectiveness of Ca2+, vitamin D, and Aquamin (a marine algae product containing Ca2+, magnesium and detectable levels of 72 additional minerals) on the induction of CaSR in the CBS and HCT116 human colon carcinoma cell lines and the corresponding CaSR null cells isolated from these lines. All three agonists induced CaSR mRNA and protein expression and inhibited cellular proliferation in the parental and CaSR null cells. Aquamin was found to be most potent in this regard. Induction of CaSR expression by these agonists resulted in demethylation of the CaSR gene promoter with a concurrent increase in CaSR promoter reporter activity. However, demethylation per se did not induce CaSR transcription. Induction of CaSR expression resulted in a down‐regulated expression of tumor inducers and up‐regulated expression of tumor suppressors. Again, Aquamin was found to be most potent in these biologic effects. This study provides a rationale for the use of a multi‐mineral approach in the chemoprevention of colon cancer and suggests that induction of CaSR may be a measure of the effectiveness of chemopreventive agents. © 2013 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111913/1/mc22123.pd

Approximation Algorithm for Line Segment Coverage for Wireless Sensor Network

The coverage problem in wireless sensor networks deals with the problem of covering a region or parts of it with sensors. In this paper, we address the problem of covering a set of line segments in sensor networks. A line segment ` is said to be covered if it intersects the sensing regions of at least one sensor distributed in that region. We show that the problem of finding the minimum number of sensors needed to cover each member in a given set of line segments in a rectangular area is NP-hard. Next, we propose a constant factor approximation algorithm for the problem of covering a set of axis-parallel line segments. We also show that a PTAS exists for this problem.Comment: 16 pages, 5 figures