Colchicine resistance

Druley, T.E., Stein, W.D., Ruth, A., and Roninson, l.B. (2001) P-glycoprotein-mediated colchicine resistance in different cell lines correlates with the effects of colchicine on P-glycoprotein conformation. Biochemistry, 40 (14). 4323 331. 

A comparative study of transport kinetics between [ Tc]MIBI and [ Tc]Tetrofosmin in drug-sensitive cells and its resistant counterparts demonstrated that functional activity of Pgp can be detected with equal sensitivity with both radiotracers. The steady-state accumulation of [ " Tc]Tetrofosmin in a human epidermoid carcinoma cell line KB 3-1 (59.4 3.0 fmol/mg protein) and its colchicine-resistant derivative KB 8-5 (1.9 0.06 fmol/mg protein) were approximately half of the values obtained for [ Tc]MIBI in the same cells (104.6 4.1 and 2.85 0.1 fmol/mg protein, respectively). Nevertheless the ratio of cell accumulation (KB 3-1/KB 8-5) for [ Tc]Tetrofosmin (43.7) was similar to that obtained for [ Tc]MIBI (37.4), suggesting that both tracers could detect Pgp expression with the same efficacy. The lower cellular accumulation of [ Tc]Tetrofosmin compared with [ Tc]MIBI was systematically reported in independent studies with different resistant cell lines [68,75], a fact that is probability related with the individual characteristics of each radiotracer. In fact, despite having similar characteristics, these tracers are not identical. [99mTc]Tetrofosmin is less sensitive than [ Tc]MIBI to the electric transmembrane potentials generated in living cells. Moreover, whereas [ Tc]MIBI accumulates preferentially in mitochondria, [ Tc]Tetrofosmin remains in cytoplasm and only a small part is sequestered in mitochondria. 

Several groups of drugs that bind to tubulin at different sites interfere with its polymerization into microtubules. These drugs are of experimental and clinical importance (Bershadsky and Vasiliev, 1988). For example, colchicine, an alkaloid derived from the meadow saffron plant Colchicum autumnale or Colchicum speciosum), is the oldest and most widely studied of these drugs. It forms a molecular complex with tubulin in the cytosol pool and prevents its polymerization into microtubules. Other substances such as colcemid, podophyllotoxin, and noco-dazole bind to the tubulin molecule at the same site as colchicine and produce a similar effect, albeit with some kinetic differences. Mature ciliary microtubules are resistant to colchicine, whereas those of the mitotic spindle are very sensitive. Colchicine and colcemid block cell division in metaphase and are widely used in cytogenetic studies of cultured cells to enhance the yield of metaphase plate chromosomes. 

Human KB carcinoma cells resistant to vinblastine and other drugs have been shown to exhibit increased membrane vesicular binding of tritiated vinblastine, and this binding is correlated with photoaffinity labeling of a 150,000- to 170,000-dalton protein in the vesicles. Labeling of this protein is inhibited by vinblastine, vincristine, and verapamil but not by colchicine (79). The failure of colchicine to inhibit the labeling of the membrane protein is unexpected since the cells from which the protein was isolated are resistant to colchicine as well as vinblastine. 

In this situation, cell lines are shown to be resistant to colchicine, doxorubicin, vinblastine, and actinomycin D. This syndrome is accompanied by an increase in measurable membrane glycoprotein (the P-170 or permeability glycoprotein). It is believed that this protein transports hydrophobic chemicals out of cells and thereby prevents drug action. Current efforts to inhibit this efferent transport protein are currently underway but, sadly, have to date been largely unsuccessful (i5). 

Persistent chronic gouty arthritis resistant to systemic therapy with colchicine and/or NSAIDs and/or corticosteroids is relieved by intraarticular corticosteroids. 

Bebawy et al. [186] demonstrated that CPZ (9) and vinblastine inhibited each other s transport in a human lymphoblastic leukemia cell line (CCRF-CEM/VLBioo). CPZ (9) reversed resistance to vinblastine but not to fluores-cently labeled colchicine and it increased resistance to colchicine. Colchicine was supposed to be transported from the inner leaflet of the membrane and vinblastine from the outer leaflet. CPZ (9) was assumed to be located in the inner membrane leaflet where it interacts with anionic groups of phospholipids and it may inhibit vinblastine transport via allosteric interactions. The authors concluded that transport of P-gp substrates and its modulation by CPZ (9) (or verapamil (79)) are dependent on substrate localization inside the membrane. Contrary to CPZ (9) location in the inner leaflet of the membrane, other modulators and substrates of P-gp were proved to be rather localized within the interface region of the membrane. The location of seven P-gp substrates and two modulators within neutral phospholipid bilayers was examined by NMR spectroscopy by Siarheyeva et al. [129]. The substrates and the modulators of P-gp were found in the highest concentrations within the membrane interface region. The role of drug-lipid membrane interactions in MDR and its reversal was reviewed in detail elsewhere [53,187]. 

Ueda K, Cardarelli C, Gottesman MM, Pastan I. Expression of a full-length cDNA for the human MDR1 gene confers resistance to colchicines, doxorubicin, and vinblastine. PNAS 1987 84 3004-3008. 

Fig. 7 The location on tubulin of residues that modulate the sensitivity to MT-destabilizing agents and the location of exogenous inhibitor and nucleotide sites on P tubulin. The a subunit is in semitransparent pink together with a composite P-subunit color-coded as in Fig. 3a with ball-and-stick models of bound taxol (orange), colchicine (yellow) and GDP (magenta). Ball-and-stick models of vinblastine (cyan) are drawn on the two partial vinca sites on a and on P tubulin. The sulfur atom of Cys P12 is highlighted as a yellow sphere. The sites of nine amino acid substitutions [49] that both confer resistance to vinblastine and colchicine and stabilize MTs are depicted as red (on a tubulin) or green (on P tubulin) spheres. Two residues of the P H10 helix whose mutations enhance the sensitivity to colchicine site ligands and destabilize MTs [71] are also shown as blue spheres...

Welwistatin also inhibits cell proliferation with reversible depletion of cellular microtubules in ovarian carcinoma cells and A-10 vascular smooth muscle cells by inhibiting the polymerization of tubulin, but it does not alter the ability of tubulin to bind [3H]colchicine or to hydrolyze GTP [8]. Due to the cytotoxicity associated with the inhibition of tubulin polymerization, which is the main mechanism of action of antitumor drugs such as vincristine and vinblastine, and because P-gp-overexpressing cells show virtually no resistance to welwistatin due to its MDR reversal properties, this natural product could be a good candidate in the chemotherapy of drug-resistant tumors. 

The hatomarubigins, isolated from Streptomyces sp. 2238-SVT4, are antitumor antibiotics which enhance the cytotoxicity of colchicine against multidrug-resistant KB cancer cells (human squamous cell carcinoma) [142, 143], Structures 202 - 204 show a rare 11-OH group hatomarubigin C (203) is a reduc-... 

Focused use of microarrays to generate large gene expression data sets relevant to transporters has been rare. To date these microarrays have been limited in the number of transporters present on them [8]. They have been used in an attempt to correlate pharmacokinetic properties with gene expression, for example, for valacyclovir [79], as well as to understand the transporter expression profile in different tissues or cell lines upon dietary component or xenobiotic treatment [1]. The lack of transporters on many commercially available microarrays has prompted some groups to produce arrays with a heavier emphasis on transporters. These arrays have, for example, then been used to demonstrate the upregulation of ABC transporters and dowmegulation of GST-Pi in cell lines resistant to colchicines or... 

Corticosteroids may be used to treat acute attacks of gouty arthritis, but they are reserved primarily for resistant cases or for patients with a contraindication to colchicine and NSAID therapy. Doses of 40 to 80 USP units of adrenocorticotropic hormone gel are given intramuscularly every 6 to 8 hours for 2 to 3 days, and then the doses are reduced in stepwise fashion and discontinued. Intra-articular administration of triamcinolone hexacetonide in a dose of 20 to 40 mg may be useful in treating acute gout limited to one or two joints. Prednisone may be administered orally in doses of 30 to 60 mg for 3 to 5 days in patients with multiple-joint involvement. Because rebound attacks may occur on steroid withdrawal, the dose should be tapered gradually by 5-mg decreases over 10 to 14 days and discontinued. 

Recurrences of acute gouty arthritis may be prevented with continuous low-dose daily oral colchicine or by uric acid-lowering therapy with either uricosuric agents or inhibition of xanthine oxidase with allopurinol. Combination therapy consisting of colchicine plus a uricosuric agent or allopurinol may be employed in resistant cases. The choice of treatment depends on the serum urate concentration, the amount of uric acid excreted in a 24-hour period, and the renal function stams of the patient. 

Prophylactic therapy with low-dose oral colchicine, 0.5 to 0.6 mg twice daily, may be effective in preventing recurrent arthritis in patients with no evidence of visible tophi and a normal or slightly elevated serum urate concentration. Patients do not become resistant to or tolerant of daily colchicine, and if they sense the beginning of an acute attack, they should increase the dose to 1 mg every 2 hours in most instances the attack will abort after 1 or 2 mg of colchicine. If the serum urate concentration is within the normal range and the patient has been symptom-free for 1 year, maintenance colchicine may be discontinued. The patient should be advised, however, that discontinuation of the treatment program may be followed by an exacerbation of acute gouty arthritis. 

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