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Abstract: Reduced drug accumulation due to overexpression of individual members of the ATP binding cassette (ABC) superfamily of membrane transporters has been investigated as a cause of multidrug resistance and treatment failure in oncology. This study was designed to develop an immunohistochemical assay to determine the expression and localization of the 72kDa ABC half-transporter ABCG2 in normal tissues. Formalin-fixed, paraffin embedded archival tissue from 31 distinct normal tissues with an average of eight separate tissue samples of each were immunostained with rabbit-anti-ABCG2 antibody 405 using a modified avidin–biotin procedure. As a negative control, each sample was also stained with antibody pre-adsorbed with peptide to assess background staining. As a means of verification, selected tissues were also stained with the commercially available monoclonal antibody 5D3. ABCG2 positivity was consistently found in alveolar pneumocytes, sebaceous glands, transitional epithelium of bladder, interstitial cells of testes, prostate epithelium, endocervical cells of uterus, squamous epithelium of cervix, small and large intestinal mucosa/epithelial cells, islet and acinar cells of pancreas, zona reticularis layer of adrenal gland, kidney cortical tubules and hepatocytes. Placental syncytiotrophoblasts showed both cytoplasmic and surface staining. Our results support a hypothesis concluding that ABCG2 plays a role in the protection of organs from cytotoxins. However, many of the cell types expressing ABCG2 have a significant secretory function. These data suggest a dual function for ABCG2 in some tissues: the excretion of toxins and xenobiotics including anti-cancer agents and a potential, as-yet undefined role in the secretion of endogenous substrates. [Copyright &y& Elsevier]

The article discusses a research study which examined the association between survival and occult metastases detected by immunochemical staining of sentinel lymph nodes and bone marrow specimens from female patients with early-stage invasive breast cancer. Results of immunochemical staining showed that 76.3 percent of the SLN specimens were tumor-negative and 10.5 percent were tumor-positive, while 3.0 percent of bone marrow specimens were positive for tumors. Data reveals that 435 patients had died and 376 had disease recurrence. Evidence showed the insignificant association of SLN metastases with overall survival, while bone marrow metastases were found to be associated with decreased overall survival.

The article discusses application of fine-needle aspiration (FNA) to reverse-phase protein microarray (RPPM) technology. It is suggested that this study can help the development of rational drug targets. It also offers that data on protein-DNA interactions during tumorigensis may help in the development of therapeutic strategies for a patient's molecular profile. Also discussed are breast cancer, proteomics, and RPPM's sensitivity and precision.

Recent studies have characterized the ABC half-transporter associated with mitoxantrone resistance in human cancer cell lines. Encoded by the ABCG2 gene, overexpression confers resistance to camptothecins, as well as to mitoxantrone. We developed four polyclonal antibodies against peptides corresponding to four different epitopes on the mitoxantrone resistance-associated protein, ABCG2. Three epitopes localized on the cytoplasmic region of ABCG2 gave rise to high-affinity antibodies, which were demonstrated to be specific for ABCG2. Western blot analysis of cells with high levels of ABCG2 showed a single major band of the expected 72-kDa molecular size of ABCG2 under denaturing conditions. Immunoblot analysis performed under non-reducing conditions and after treatment with cross-linking reagents demonstrated a molecular weight shift from 72 kDa to several bands of 180 kDa and higher molecular weight, suggesting detection of dimerization products of ABCG2. Evidence of N-linked glycosylation was also obtained using tunicamycin and N-glycosidase F. Finally, both by light, fluorescence and electron microscopic immunohistochemical staining, we demonstrate cytoplasmic and predominantly plasma membrane localization of ABCG2 in cell lines with high levels of expression. Plasma membrane staining was observed on the surface of the chorionic villi in placenta. These results support the hypothesis that ABCG2 is an ABC half-transporter that forms dimers in the plasma membrane, functioning as an ATP-dependent outward pump for substrate transport. [Copyright &y& Elsevier]

The objective of the present study was to characterize the genitourinary syndromes that accompany indinavir-associated pyuria. Of 23 indinavir-treated patients with persistent pyuria, 4 had isolated interstitial nephritis, 10 had both interstitial nephritis and urothelial inflammation, 7 had isolated urothelial inflammation, and 2 had pyuria with nonspecific urinary tract inflammation. A total of 21 patients had multinucleated histiocytes identified by cytologic testing of urine specimens. Urine abnormalities resolved in all 20 patients who stopped receiving indinavir therapy. Pyuria continued in the 3 patients who continued receiving indinavir. Six patients had elevated serum creatinine levels, which returned to baseline levels when indinavir was discontinued. In conclusion, indinavir-associated pyuria was frequently associated with evidence of interstitial nephritis and/or urothelial inflammation, multinucleated histiocytes were commonly present in urine specimens, and cessation of indinavir therapy was associated with prompt resolution of urine abnormalities. [ABSTRACT FROM AUTHOR]