title: Constitutive expression of multidrug resistance in human colorectal tumours and cell lines.
abstract: In this study we report detection of mdr1 gene expression in the liver metastases of 7/11 patients with colon carcinoma and characterise the MDR phenotype associated with a panel of 19 human colon carcinoma cell lines. Within this panel, mdr1 mRNA biosynthesis and surface localisation of Pgp were assessed with respect to MDR functionality where the cell lines are representative of different clinical stages of tumour progression, metastatic potential and differentiation. The data indicates that constitutive levels of mdr1 mRNA/Pgp expression may not necessarily result in the functional expression of the MDR phenotype. While low levels of mdr1 mRNA/Pgp were detected in 5/8 well differentiated colon cell lines, only 2/8 were functionally MDR. In contrast, 10/11 moderate and poorly differentiated lines expressed mdr1 mRNA/Pgp and of these, 9/11 were functionally MDR. The phosphorylation status of the mature 170 kD P-glycoprotein and the surface localisation of this glycoprotein showed the strongest correlation with functionality. Analysis of cell lines for cross-resistance and chemosensitivity profiles against a battery of chemotherapeutic drugs suggests multiple mechanisms, in addition to Pgp, contribute to the overall resistance of colorectal cancer.
authors.affiliation: Lederele Laboratories, Oncology Research Section, Pearl River, New York 10965.
authors.forename: R
authors.initials: R
authors.lastname: Kramer
authors.forename: T K
authors.initials: TK
authors.lastname: Weber
authors.forename: B
authors.initials: B
authors.lastname: Morse
authors.forename: R
authors.initials: R
authors.lastname: Arceci
authors.forename: R
authors.initials: R
authors.lastname: Staniunas
authors.forename: G
authors.initials: G
authors.lastname: Steele
authors.forename: I C
authors.initials: IC
authors.lastname: Summerhayes
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002352:Carrier Proteins / Q000502:physiology*; D015179:Colorectal Neoplasms / Q000235:genetics / Q000503:physiopathology*; D004351:Drug Resistance; D015870:Gene Expression; D006801:Humans; D066298:In Vitro Techniques; D008113:Liver Neoplasms / Q000235:genetics / Q000556:secondary; D008207:Lymphatic Metastasis; D008562:Membrane Glycoproteins / Q000502:physiology*; D009362:Neoplasm Metastasis; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm