Retinoic-acid-resistant neuroblastoma cell lines show altered MYC regulation and high sensitivity to fenretinide.

BACKGROUND: High-dose, pulse-13-cis-retinoic acid (13-cis-RA) given after intensive cytotoxic therapy improves event-free survival for high-risk neuroblastoma (NB), but more than 50% of patients have tumor recurrence. PROCEDURE: We conducted multistep selection for resistance to all-trans-retinoic acid (ATRA) in NB cell lines with (SMS-KCNR and LA-N-5) or without (SMS-LHN) MYCN genomic amplification. RESULTS: After 12 exposures to 10 microM ATRA, the two MYCN-amplified cell lines (KCNR 12X RR and LA-N-5 12X RR) showed partial resistance to the cytostatic/differentiation effects of ATRA; complete resistance was seen in LHN 12X RR. ATRA-selected cells showed general RA resistance (cross-resistance to 13-cis-RA). Transient (KCNR 12 X RR, LA-N-5 12X RR) or sustained (LHN 12X RR) novel overexpression of c-myc was associated with RA resistance. RA-insensitive overexpression of MYCN by transduction in SMS-LHN also conferred RA resistance. Both parental and RA-resistant lines showed 2-4 logs of cell kill in response to N-(4-hydroxyphenyl)retinamide (4- HPR, fenretinide). Compared to parental lines, 4-HPR achieved 1-3 log greater cell kills in RA-resistant LHN 12X RR, LA-N-5 12X RR, KCNR 12X RR, and MYCN-transduced SMS-LHN or SK-N-RA. NB cell lines (n = 26) from 21 different patients showed that 16 of 26 (62%) were sensitive to 4-HPR (LC(90) < 10 microM), including lines established at relapse after myeloablative and/or 13-cis-RA therapy. CONCLUSION: Thus, RA-resistant NB cell lines can be sensitive (and in some cases collaterally hypersensitive) to 4-HPR.

Postmenopausal hormone use following a 3-year randomized clinical trial.

Postmenopausal women often discontinue estrogen therapy within the first year. No studies have examined reasons why women continue or discontinue hormone replacement therapy (HRT) after several years of use, when hormone side effects have subsided. We wanted to identify determinants of estrogen use after participation in a 3-year randomized placebo-controlled trial. The Postmenopausal Estrogen/Progestin Intervention (PEPI) study compared the effects of estrogen alone or in combination with one of three progestogens with placebo. Post-PEPI use of hormone therapy was ascertained 1-4 years after the trial in 775 (90%) of the originally enrolled women. Potential correlates of treatment decisions were identified from sociodemographic characteristics, medical histories, and clinical measures ascertained at baseline and during and after the trial. Among women who had been assigned to placebo during PEPI, post-PEPI hormone use was significantly less common in women who were adherent to placebo during PEPI, older, or of non-Caucasian ethnicity. Hormone use was positively associated with hysterectomy. Among women assigned to an active regimen during PEPI, post-PEPI hormone use was significantly more common in women who used hormones before PEPI and in women who were adherent to hormones during PEPI. Older age, less education, and being non-Caucasian predicted less hormone use. Post-PEPI hormone use was highest in San Diego and lowest in Iowa City. Women on placebo who lost more bone mineral density (BMD) were more likely to begin hormones than women with less bone loss. Lipids, blood pressure, and other cardiovascular risk factors had relatively little influence on hormone use. The main predictors of post-PEPI hormone use were those associated with use in the general population (education, ethnicity, geographical region, hysterectomy, and prior use/adherence).

Expression of protein gene product 9.5 and tyrosine hydroxylase in childhood small round cell tumors.

Small round cell tumors of childhood can be histologically ambiguous, can require tumor markers for an accurate diagnosis, and include neuroblastoma, peripheral primitive neuroectodermal tumor (pPNET), Ewing's sarcoma (ES), lymphoma, and rhabdomyosarcoma. Because the cell type of origin for ES remains controversial, characterizing gene expression in ES can provide diagnostic markers and lead to better understanding of tumor biology. We studied RNA expression of the neuronal genes protein gene product 9.5 (PGP 9.5) and tyrosine hydroxylase (TH) by Northern analysis in cell lines and tissue from small round cell tumors. PGP 9.5 showed strong expression in 17 of 17 neuroblastoma cell lines, 9 of 9 pPNET cell lines, and 11 of 11 ES cell lines. PGP 9.5 was weakly expressed in 1 of 1 alveolar rhabdomyosarcoma cell lines but not in 1 of 1 embryonal rhabdomyosarcomas, and weak expression was seen in 1 of 7 leukemia cell lines. In tumor tissue, all 12 neuroblastomas expressed PGP 9.5, as did all 7 pPNET and all 7 ES. PGP 9.5 was very weakly expressed in 6 of 9 rhabdomyosarcomas and 1 of 9 lymphomas. TH was expressed only in neuroblastomas, and no TH expression was seen in cell lines or tissue from other tumors. As high expression of PGP 9.5 was only found in neural tumors; PGP 9.5 expression by ES provides further evidence for a neural origin of this tumor, whereas TH expression is highly specific for neuroblastomas. PGP 9.5 expression should allow sensitive detection of minimal residual disease for ES and pPNET using reverse transcription-PCR, and the variability in TH and PGP 9.5 expression levels in neuroblastomas indicates that expression of both genes should be used for monitoring minimal residual disease by reverse transcription-PCR.

Human neuroblastoma cell lines that express N-myc without gene amplification.

BACKGROUND: About one half of aggressive neuroblastomas lack N-myc amplification. Cell lines from such tumors are needed to determine the biological basis of aggressive tumor behavior. METHODS: Neuroblastoma cell lines were established from a primary tumor (SMS-LHN) and a bone marrow metastasis (LA-N-6) of two children with Stage IV neuroblastoma. Although both cell lines and their original tumors lacked N-myc genomic amplification, these patients died of progressive disease. RESULTS: SMS-LHN and LA-N-6 can be distinguished from primitive neuroectodermal tumor (PNET) lines by cell surface antigen expression and catecholamine production. Cytogenetic analysis of each cell line revealed unique genetic rearrangements, whereas both lines showed abnormalities involving chromosome 2. Neither cell line contained double-minute chromosomes, homogeneously staining regions, a 1p chromosomal deletion, or t(11;22). The growth rates of these two new lines in vitro and in vivo (as xenografts in nude mice) are slower than N-myc amplified neuroblastoma lines. Both lines express greater amounts of N-myc RNA and protein relative to nonneuroblastoma cell lines (including PNET), although not to the extent of cell lines with N-myc genomic amplification. CONCLUSIONS: The relatively large amount of N-myc expression in these two new cell lines suggests that N-myc expression without amplification could play a role in the pathogenesis of some neuroblastomas. These cell lines should be useful for investigating mechanisms and consequences of N-myc gene activation other than genomic amplification.