Differential expression of the enzyme that esterifies retinol, lecithin:retinol acyltransferase, in subtypes of human renal cancer and normal kidney.

PURPOSE: Retinoids, a group of compounds, including vitamin A (retinol), and related metabolites, have been shown to regulate the growth and differentiation of many types of cells. IFN-alpha and either 13-cis-retinoic acid or liposomal all-trans retinoic acid have been used in the treatment of patients with metastatic renal cell carcinoma. We knew that samples from renal cell carcinomas contained greatly reduced levels of retinol and retinyl esters relative to samples from normal human kidney. This prompted us to examine the levels of LRAT (lecithin:retinol acyltransferase) protein in various subtypes of human kidney cancers relative to normal human kidney by immunohistochemistry. EXPERIMENTAL DESIGN: We examined 31 partial or radical nephrectomy specimens diagnosed with kidney tumors between 1997 and 1998. Representative paraffin-embedded tissue blocks from each tumor, with each containing adjacent nonneoplastic renal parenchyma, were used for immunohistochemical analysis with affinity purified antibodies to human LRAT protein. RESULTS: LRAT protein was detected at high levels in the epithelial cells in the tubules and the lining of Bowman's capsule in the glomeruli of normal, nonneoplastic kidney sections. Among the 31 tumors, there were 13 cases of conventional (clear cell) renal cell carcinoma (RCC; including 2 multilocular cystic RCCs), 7 papillary RCC, 6 chromophobe RCC, 1 RCC, unclassified, and 4 renal oncocytoma. All tumors showed diffuse immunoreactivity for LRAT. In each case, the staining was uniform throughout the tumor, with only minimal variation in the staining intensity between different areas. All 4 renal oncocytomas, 2 of 6 chromophobe RCCs, 1 conventional (clear cell) carcinoma, 1 RCC, unclassified, and 2 conventional RCCs, which were of the multilocular cystic-type stained strongly (3+) for LRAT. In contrast, the remaining conventional RCCs and the papillary RCC samples stained much less intensely for LRAT. Of the 10 tumors that stained 3+ for LRAT in the study, 9 were either benign tumors or tumors with low malignant potential. CONCLUSIONS: These data show that LRAT expression is higher in renal tumors with an indolent biological behavior. Additional studies will ascertain if LRAT possesses any prognostic or therapeutic role in renal cancer.     

Regulation of keratin 19 gene expression by estrogen in human breast cancer cells and identification of the estrogen responsive gene region

Estrogens regulate the proliferation, cytoarchitectural, and invasive properties of estrogen receptor (ER)-containing breast cancer cells. To identify genes under direct regulation by estrogen in breast cancer cells, we have used representational difference analysis (RDA) of cDNAs. In this way, we have identified (cyto)keratin 19 (K19), a major component of cell intermediate filaments, as being under rapid and direct regulation by estrogen in MCF-7 cells. Stimulation by estradiol (E2) of K19 mRNA is rapid, with maximal increase at 3 h, and is not blocked by cycloheximide, suggesting that it is a primary response to the hormone. Increased accumulation of K19 protein is observable by 8 h after E2 and levels continue to increase at 24-48 h after E2 treatment. Suppression of E2-induced K19 gene expression by the antiestrogen ICI 182,780 suggests that ER mediates this regulation. Analysis of the human K19 chromosomal gene, by transient transfection assays employing reporter gene constructs with the 5' and 3' flanking regions and portions of the body of the K19 gene, has resulted in identification of a complex enhancer region in the first intron. This enhancer region consists of a near-consensus estrogen response element (K19 ERE, which differs by only 1 bp from the consensus ERE) and two ERE half sites, as well as two AP1-like sites. The results of transfections with either the K19 gene promoter or the heterologous thymidine kinase promoter and constructs containing mutated or deleted portions of the enhancer region show that the K19 ERE is responsible for the E2-dependent transactivation of the keratin 19 gene and for the synergism that is observed between E2 and TPA with both ER alpha and ER beta. These studies document ER regulation of the K19 gene, localize the estrogen responsive region, and suggest that up-regulation of keratin 19 gene expression by estrogen may contribute to the cytoskeletal and nuclear matrix reorganization, and increased metastatic potential of ER-containing breast cancer cells upon exposure to estrogens.     

Phase I trial of interferon alpha2b and liposome-encapsulated all-trans retinoic acid in the treatment of patients with advanced renal cell carcinoma

BACKGROUND: Studies suggest that retinoic acid (RA) can augment the antitumor effects of interferon-based therapy in patients with advanced renal cell carcinoma (RC); however, this benefit has not been achieved convincingly using oral formulations of 13-cis RA and all-trans RA. Liposome-encapsulated all-trans RA (ATRA-IV) has improved pharmacokinetics with increased and prolonged ATRA serum levels compared with oral retinoids. METHODS: Cohorts of 3-6 patients with progressive metastatic RC received a dose of 3 MU interferon alpha2b per day subcutaneously, which was escalated weekly to 5 MU and then to 10 MU, plus ATRA-IV beginning at a dose of 90 mg/m(2) intravenously three times per week (Monday, Wednesday, and Friday), with a planned escalation to a maximum of 140 mg/m(2). RESULTS: Two of the initial five patients experienced Grade 3 leukopenia while receiving 3 MU interferon and 90 mg/m(2) ATRA-IV. Therefore, the trial was amended to begin ATRA-IV at a dose of 15 mg/m(2) three times per week with a planned escalation by 15 mg/m(2) per cohort plus interferon-alpha at a dose of 3 MU subcutaneously 5 days per week (Monday through Friday), which was escalated weekly to 5 MU and then to 10 MU. Twelve patients were treated on the revised schedule. Toxicity was mild and included Grade 2 anemia (n = 7 patients), leukopenia (n = 2 patients), nausea (n = 2 patients), fatigue (n = 2 patients), fever (n = 2 patients), hepatic toxicity (n = 1 patient), edema (n = 1 patient), neurocortical toxicity (n = 1 patient), headache (n = 1 patient), and infection (n = 1 patient). One patient developed hyperthyroidism, and one patient required admission for bacteremia from a line infection. Dose limiting toxicity was Grade 3 hepatic toxicity, which was observed at a dose of 30 mg/m(2) ATRA-IV in 2 of 6 patients. Only 2 of 12 patients agreed to a dose escalation up to 10 MU interferon-alpha. Of 12 patients who were evaluable for response, 2 patients (17%) had a partial response in bone and lung, including 1 partial response of > 91 weeks' duration, at a dose of 15 mg/m(2) ATRA-IV three times per week and 5 MU interferon-alpha. Five additional patients experienced stable disease, two of whom had disease progression in bone only. CONCLUSIONS: The acceptable toxicity profile and preliminary efficacy results suggest that this regimen warrants further evaluation. ATRA-IV (15 mg/m(2) TIW) and interferon-alpha (3 MU Monday through Friday escalated weekly to 5 MU and to 7 MU) are recommended for further study in patients with advanced RC.     

P-Glycoprotein Is Positively Correlated with p53 Protein Accumulation in Human Colorectal Cancers

To explore the relationship between mutant p53 and Pgp expression, we have examined the levels of both proteins in human colorectal adenocarcinomas. Serial frozen sections of 40 surgical samples were stained with an anti-Pgp (MRK16) and two different anti-p53 protein antibodies (Abs), PAb421 and Pabl80l. Nineteen (47.5%) of 40 samples examined were positive for Pgp, and 18 (45%) of 40 were positive for p53. The samples that stained positively with PAb421 also stained positively with Pahl80l. Pgp expression was detected in 13 (76.5%) of 17 samples that were positive for p53 using PAb421 and in 15 (83.3%) of 18 samples that were positive for p53 using Pabl80. Thus, we found that p53 and Pgp were co-expressed in a significant number of samples ( P < 0.002). There was no relationship between Pgp or p53 protein accumulation and histologic grade or stage. The present results demonstrate that Pgp expression is closely associated with p53 protein accumulation in human colorectal cancers. These data provide evidence to support the idea that mutant p53 activates the MDR1 gene in vivo .     

CANCER BIOLOGY: Drug-resistant breast cancer cells frequently retain expression of a functional wild-type p53 protein

Abnormalities in the p53 tumor suppressor gene have been shownto affect cellular processes related to cell cycle control andgene amplification. In this study we compare the status andfunction of wild-type p53 in MCF-7 breast cancer cells withsublines selected for resistance to chemo-therapeutic agentshaving different mechanisms of action. Sublines that were resistantto melphalan, pyrazafurin, mitoxantrone, etoposide and PALAall retained expression of wild-type p53. Methotrexate-resistantMCF-7 cells were unusual heterozygotes that expressed a wild-typeand dominant, in-frame p53 deletion mutant and the doxorubicin-resistantcells expressed only mutant p53. Analysis of the Gl checkpointafter treatment with ionizing radiation revealed that the pyrazafurin-,melphalan- and mitoxan-trone-resistant cells arrested stronglyin Gl. The etoposide-and PALA-resistant cells had an intermediateGl arrest phenotype and the methotrexate- and doxorubicin-resistantcells had a minimal Gl arrest phenotype. mRNA and protein analysesof downstream effector genes, including p21^CIP1A/Waf1, mdm2,Gadd 45 and the retinoblastoma protein, did not entirely differentiatesublines having a strong versus intermediate Gl arrest phenotype.Neither the p53 status nor the strength of the Gl arrest couldbe correlated with cell survival after ionizing radiation. Whendrug-sensitive MCF-7 cells were treated with the same chemotherapeuticagents, p53 and p21^CIPI/Waf1 levels increased between 2-and14-fold. Together these data suggest that other cellular factorslikely play a role in overcoming the inhibitory effects of ionizingradiation on p53 in drug-resistant breast cancer cells.