ABCMdb

PMID: 16337740

Cervenak J, Andrikovics H, Ozvegy-Laczka C, Tordai A, Nemet K, Varadi A, Sarkadi B
The role of the human ABCG2 multidrug transporter and its variants in cancer therapy and toxicology.
Cancer Lett. 2006 Mar 8;234(1):62-72. Epub 2005 Dec 7., 2006-03-08 [PubMed]

Sentences

No. Mutations Sentence Comment

5 ABCG2 p.Arg482Thr Interestingly, a single nucleotide mutation, changing amino acid 482 from arginine to threonine or glycine in ABCG2, results in a major increase in the catalytic activity and a wider drug recognition by this protein. Login to comment 80 ABCG2 p.Arg482Thr ABCG2 p.Arg482Gly ABCG2 p.Arg482Met The cDNA sequence analysis of the MCF-7/AdVP3000 human breast cancer cell line and the S1M1-80 human colon cancer cell line revealed that in these cell lines, each showing anthracycline resistance and an ability to extrude rhodamine 123, a single amino acid change occurred at position 482, resulting an R482T (c.1445GOC) mutant in the MCF-7/AdVP3000 cell line, an R482G replacement (c.1444AOG) in S1M1-80 cells, and an R482M substitution (c.1445GOT) in the MT-4/DOX500 human T cell line [27,41,54]. Login to comment 81 ABCG2 p.Arg482Ser ABCG2 p.Arg482Met Moreover, in the 88.6/D800-A, 88.6/D800-B and KOT52/ D800 mouse fibroblast cell lines, an R482M (KOT52/D800 and 88.6/D800-A cells) and an R482S (88.6/D800-B cells) mutation was observed, with a similar, anthracycline resistant phenotype [42]. Login to comment 87 ABCG2 p.Arg482Thr ABCG2 p.Arg482Gly In vitro experiments revealed that the expression of the wild-type, R482G and R482T variant forms of ABCG2 in HEK-293 cells conferred 15-fold, 47-fold, and 54-fold resistance against mitoxantrone, respectively [50]. Login to comment 88 ABCG2 p.Arg482Thr ABCG2 p.Arg482Gly It was also demonstrated that the R482G and R482T mutants showed an increased transport activity for various compounds and increased ATP hydrolytic activity in Sf9 cell membranes [51]. Login to comment 94 ABCG2 p.Thr153Met ABCG2 p.Ala149Pro ABCG2 p.Pro269Ser ABCG2 p.Arg163Lys In addition to the aa 482 ABCG2 mutations, several other variants [c.445GOC (A149P), c.458COT (T153M), c.488GOA (R163K), c.805COT (P269S)] leading to coding sequence changes were identified in different cell lines that were also not detected in healthy individuals [47,55]. Login to comment 95 ABCG2 p.Thr153Met In cases of in vitro expression, the above ABCG2 variants except for T153M which was not tested, did not show any differences from the wild-type ABCG2 protein, neither in their subcellular localization in LLC-PK1 polarized cells, nor in their estrone sulphate, DHEAS (dehydroepiandrosterone sulfate), methotrexate or PAH (p-aminohippurate) transport. Login to comment 97 ABCG2 p.Ala24Val ABCG2 p.Gln166Glu ABCG2 p.Phe208Ser According to the first cloning studies, the ABCG2 cDNA obtained from normal human placenta [8] showed the following sequence alterations, as compared to the database reference sequence: c.71COT (A24V), c.496COG (Q166E) and c.623TOC (F208S). Login to comment 103 ABCC1 p.Arg433Ser Another report showed that a naturally occurring mutation of R433S in MRP1 caused decreased organic anion transport and J. Cervenak et al. / Cancer Letters 234 (2006) 62-72 65 increased doxorubicin resistance [73]. Login to comment 109 ABCG2 p.Gln141Lys ABCG2 p.Val12Met ABCG2 p.Ile206Leu ABCG2 p.Asn590Tyr ABCG2 p.Asp620Asn ABCG2 p.Ser441Asn ABCG2 p.Phe489Leu ABCG2 p.Phe431Leu ABCG2 p.Gln126* To date, altogether eight non-synonymous (V12M, Q141K, I206L, F431L, S441N, F489L, N590Y, D620N), five synonymous (silent) (c.114TOC, c.369COT, c.474COT, c.1098GOA, c.1425AOG) missense mutations, one nonsense (Q126X), and one frameshift (c.1515delC) mutations were identified in the coding region of ABCG2 in healthy individuals or in patients [43-46,49,63-65]. Login to comment 110 ABCG2 p.Gln141Lys ABCG2 p.Val12Met Among the above variations, affecting the protein structure, two alterations [c.34GOA (V12M), c.421CO A (Q141K)] have been reported to be polymorphic in several populations. Login to comment 112 ABCG2 p.Ile206Leu ABCG2 p.Asn590Tyr ABCG2 p.Asp620Asn ABCG2 p.Ser441Asn ABCG2 p.Phe489Leu ABCG2 p.Phe431Leu ABCG2 p.Gln126* Some of the above sequence variations showed an allele frequency of about 1% in distinct populations (Q126X, F489L in the Japanese and N590Y in the Caucasian population [45-47,49,64]), while most of the mutations were only detected in single individuals (missense mutations: I206L, F431L, S441N, D620N, and a frameshift mutation: c.1515delC [44-46,49]). Login to comment 114 ABCG2 p.Val12Met The V12M polymorphism in exon 2 (c.34GOA) affects the N-terminal intracellular region of the protein. Login to comment 116 ABCG2 p.Val12Met The V12M polymorphism was found in all ethnic groups tested, with the highest allele frequency in Mexican-Indians (90%, but only 10 individuals were tested), while only 2% in a Swedish population [43,49]. Login to comment 117 ABCG2 p.Val12Met Upon the combination of several population studies, a consistent and significant (P!0.0001) difference can be observed between the overall allele frequencies of V12M in Caucasian/African American and Japanese populations (Table 1). Login to comment 118 ABCG2 p.Gln126* An interesting sequence variant Q126X (c.376CO T), affecting the coding region and leading to premature termination of protein synthesis, was consistently observed in certain Japanese cohorts, however, it was absent in two different Caucasian and African American groups [45,46,64]. Login to comment 119 ABCG2 p.Gln141Lys The Q141K polymorphism located in exon 5 (c.421COA) leads to the replacement of the negatively charged glutamic acid residue with a positively charged lysine residue. Login to comment 121 ABCG2 p.Gln141Lys The Q141K variant was also detected in all ethnic groups tested: the allele frequency ranged between 1 and 35%, (the African and African-American subjects with low, while the Japanese and Chinese populations with high allele frequencies) [46,63]. Login to comment 122 ABCG2 p.Val12Met Similarly to V12M, substantial and significant (P!0.0001) allele frequency differences can be observed between the three major ethnic groups tested, potentially reflecting different population admixture and unequal effects of environmental selection factors. Login to comment 123 ABCG2 p.Gln141Lys ABCG2 p.Val12Met ABCG2 p.Gln126* On the basis of definitive molecular haplotype analyses (PCR-RFLP) for the three major variants [c.34GOA (V12M), c.376COT (Q126X), c.421COA (Q141K)] in a Japanese population, four haplotypes were identified G-C-C (V-Q-Q), G-C-A (V-Q-K), A-CC (M-Q-Q), and G-T-C (V-X-Q). Login to comment 127 ABCG2 p.Gln141Lys ABCG2 p.Val12Met ABCG2 p.Gln126* The above results collectively suggest that the V12M, Q126X, and Q141K variants are likely to occur on separate chromosomes. Login to comment 130 ABCG2 p.Gln141Lys ABCG2 p.Val12Met Mainly the two major non-synonymous polymorphisms, V12M and Q141K, were investigated. Login to comment 132 ABCG2 p.Gln141Lys ABCG2 p.Val12Met Imai et al. [64] and Morisaki et al. [66] in stable mammalian expression systems found that in PA317 or HEK-293 cells the expressed Q141K ABCG2 protein had a lower expression level than the wild-type ABCG2, or the V12M variant. Login to comment 133 ABCG2 p.Gln141Lys ABCG2 p.Val12Met Morisaki et al. demonstrated that both the V12M and Q141K ABCG2 could reach the plasma membrane in the HEK-293 cells, while a significant portion of Table 1 Summary of population genetics data on naturally occurring sequence variations, affecting the coding region of the human ABCG2 gene Position in the ABCG2 genea Position in the ABCG2 cDNAb Amino acid substitution Population n C/K C/C AF (%G 95%CI) Ref. Login to comment 134 ABCG2 p.Gln141Lys ABCG2 p.Val12Met ABCG2 p.Asn590Tyr ABCG2 p.Phe489Leu ABCG2 p.Gln126* g.34GOA (exon 2) c.34GOA V12M Caucasian 150 27 2 10.3G3.5 [47] Caucasian 150 11 0 3.7G2.2 [46] Caucasian 86 n.a n.a 2.0Gn.a [49] Swedish 60 2 0 1.7G2.3 [43] Total Caucasian 360 40 2 6.1G1.8 Japanese 220 61 8 17.5G3.6 [46] Japanese 29 9 1 19.0G10.3 [64] Total Japanese 249 70 9 17.7G3.4 African-American 150 17 1 6.3G2.8 [46] g.8191COT (exon 4) c.376COT Q126X Caucasian 150 0 0 0.0 [46] Caucasian 150 0 0 0.0 [47] Total Caucasian 300 0 0 0.0 Japanese 220 4 0 0.9G0.9 [46] Japanese 124 3 0 1.2G1.4 [64] Japanese 60 2 0 1.7G2.3 [45] Total Japanese 404 9 0 1.1G0.7 African-American 150 0 0 0.0 [46] g.8825CO A (exon 5) c.421COA Q141K Caucasian 172 33 3 11.3G3.4 [63] Caucasian 150 25 4 11.0G3.6 [46] Caucasian 150 22 2 8.7G3.2 [47] Caucasian 85 n.a n.a 14.0Gn.a [49] Swedish 60 10 1 10.0G5.5 [43] Total Caucasian 532 90 10 10.3G1.9 Japanese 220 90 27 32.7G4.5 [46] Japanese 124 48 9 26.6G5.6 [64] Chinese 95 43 11 34.2G6.9 [63] Total Asian 439 181 47 31.3G3.1 African, Sub-Saharan 938 14 1 0.9G0.4 [63] African-American 150 5 1 2.3G1.7 [46] African-American 94 8 1 5.3G3.3 [63] Total Africanc 1182 27 3 1.4G0.5 g.40645AO T (exon 12) c.1465TOC F489L Japanese 100 1 0 0.5G1.0 [46] Japanese 60 1 0 0.8G1.7 [45] Total Japanese 160 2 0 0.6G0.9 g.45367AO T (exon 15) c.1768AOT N590Y Caucasian 150 1 0 0.3G0.7 [47] Caucasian 65 1 0 0.8G1.5 [49] Total Caucasian 215 2 0 0.5G0.7 Only those cDNA SNPs were listed that were detected in at least two independent studies. Login to comment 142 ABCG2 p.Gln141Lys J. Cervenak et al. / Cancer Letters 234 (2006) 62-72 67 Q141K (though having a lower expression level), remained intracellular [66]. Login to comment 143 ABCG2 p.Gln141Lys According to other studies, a 30-40% reduction in cell surface expression of the Q141K variant, although having a similar mRNA level than the wild-type ABCG2, was observed [55,64]. Login to comment 144 ABCG2 p.Gln141Lys Recent investigation of the expression level of ABCG2 in 99 Japanese placenta samples revealed that individuals homozygous for the Q141K variant showed significantly lower expression levels of this transporter protein, while the heterozygous samples displayed an intermediate expression level [46]. Login to comment 146 ABCG2 p.Gln141Lys ABCG2 p.Val12Met Mizuarai et al. expressed ABCG2 in polarized LLC-PKI cells, and by using confocal microscopy demonstrated that the wtABCG2 and Q141K showed mainly apical staining, while the V12M variant showed intracellular localization [47]. Login to comment 147 ABCG2 p.Gln141Lys ABCG2 p.Val12Met ABCG2 p.Gln166Glu ABCG2 p.Ser441Asn ABCG2 p.Ala149Pro ABCG2 p.Pro269Ser ABCG2 p.Arg163Lys In a recent study, similarly LLC-PKI cells where used to express the V12M and Q141K variants and additionally five other polymorphisms (A149P, R163K, Q166E, P269S and S441N [55]). Login to comment 148 ABCG2 p.Gln141Lys ABCG2 p.Val12Met ABCG2 p.Ser441Asn Interestingly, they found that all polymorphisms, including V12M and Q141K, had an apical localization, and only the S441N variant showed intracellular staining. Login to comment 149 ABCG2 p.Ser441Asn The impaired localization pattern of the S441N variant was accompanied by a poor expression level. Login to comment 151 ABCG2 p.Gln141Lys ABCG2 p.Gln141Lys ABCG2 p.Val12Met Clearly, more detailed studies are required to clarify the mechanism of a reduced protein expression for Q141K, and the altered cellular localization found for the V12M and Q141K variants under certain conditions. Login to comment 153 ABCG2 p.Gln141Lys ABCG2 p.Val12Met When the functions of the ABCG2 variants were examined in cytotoxicity assays, a 10-fold decrease in drug resistance, as compared to the wild-type ABCG2, was reported by Mizuarai et al., when the V12M or Q141K-transfected LLC-PKI cells were challenged by mitoxantrone, topotecan, or an indolocarbazole topoisomerase I inhibitor [47]. Login to comment 154 ABCG2 p.Gln141Lys In contrast, Morisaki et al. found that only the Q141K variant had a moderately lower level resistance against mitoxantrone, topotecan or SN-38, as compared to the wild-type ABCG2-transfected cells [66]. Login to comment 161 ABCG2 p.Gln141Lys Q141K is mapped in the functionally important ATP-binding cassette region of ABCG2 (Fig. 1) between the Walker A and the signature motifs, therefore, it is possible that the ATPase activity of this variant is altered. Login to comment 162 ABCG2 p.Gln141Lys ABCG2 p.Val12Met Two studies compared the vanadate-sensitive ATPase activity of ABCG2 V12M and Q141K variants, using Sf9 (Spodoptera frugiperda) cell membranes [47,66]. Login to comment 163 ABCG2 p.Gln141Lys A reduced, 1.3 and 1.8-fold lower basal ATPase activity was observed by Mizuarai et al. and Morisaki et al., respectively, for the Q141K than for wild-type ABCG2. Login to comment 164 ABCG2 p.Val12Met ABCG2 p.Asp620Asn On the other hand, the V12M (and D620N) ABCG2 showed a similar ATPase activity as the wild-type protein. Login to comment 182 ABCG2 p.Gln141Lys A recent investigation performed an exploratory, retrospective evaluation of the functional consequence of the ABCG2 421COA (Q141K) variant in 20 adult white patients, treated with diflomotecan [72]. Login to comment 185 ABCG2 p.Gln141Lys ABCG2 p.Gln141Lys This observation is in harmony with studies indicating a reduced protein expression and function for the Q141K variant, while seems to contradict the results of de Jong et al. As mentioned above, the allele frequency of ABCG2 421COA (Q141K) varies in diverse populations (Table 1), and in Japan and China this polymorphism appears to be common, with an overall allele frequency of 31.3G3.1%. Login to comment