Thyroid hormone resistance syndromes

A Rare Case of Partial Peripheral Thyroid Hormone Resistance Due to a Point Mutation in the Membrane Integrin Α(V)Β(3) and Concomitant Hashimoto`s Thyroiditis

BACKGROUND:

Peripheral resistance to thyroid hormones is a type of unresponsiveness of the peripheral cells or tissues to FT3 and/or FT4. Generalised resistance to thyroid hormones affects the pituitary gland and most of the peripheral tissues. Selective pituitary resistance or central resistance to thyroid hormones include unresponsiveness of the pituitary gland, but the peripheral tissues are responsive. Selective peripheral resistance involves peripheral tissue or cellular resistance to thyroid hormones, but the pituitary gland is responsive.

CASE PRESENTATION:

We present a rare case of a female patient with partial peripheral resistance to thyroid hormones due to a point mutation coding for the beta subunit of the integrin molecule α(V)β(3) and concomitant Hashimoto`s thyroiditis. Clinically, the patient`s symptoms were in favour of hypothyroidism, and the laboratory results were in favour of the secondary hyperthyroid state. PCR protein amplification detected a point mutation coding for the membrane receptor, which mediates a signal via the MAPK pathway when bonded with thyroid hormones.

CONCLUSION:

Peripheral resistance to thyroid hormones is a very rare condition and can often be misdiagnosed due to the broad spectrum of clinically similar differential diagnostic entities. Molecular analysis is required to confirm the exact underlying cause for the impaired peripheral sensitivity to thyroid hormones syndrome.

Thyroid hormone resistance and its management

The syndrome of impaired sensitivity to thyroid hormone, also known as syndrome of thyroid hormone resistance, is an inherited condition that occurs in 1 of 40,000 live births characterized by a reduced responsiveness of target tissues to thyroid hormone due to mutations on the thyroid hormone receptor. Patients can present with symptoms of hyperthyroidism or hypothyroidism. They usually have elevated thyroid hormones and a normal or elevated thyroid-stimulating hormone level. Due to their nonspecific symptomatic presentation, these patients can be misdiagnosed if the primary care physician is not familiar with the condition. This can result in frustration for the patient and sometimes unnecessary invasive treatment such as radioactive iodine ablation, as in the case presented herein.

Effect of vitamin C on the absorption of levothyroxine in patients with hypothyroidism and gastritis

BACKGROUND

Malabsorption of l-T4 is a major clinical problem. Changes in gastric pH caused by several medical illnesses are associated with difficulties in the control of patients with hypothyroidism receiving the hormone. Means to correct these alterations would be of clinical value.

OBJECTIVES

Our objective was to study the effect of vitamin C on the absorption of l-T4 in patients with hypothyroidism and gastritis.

DESIGN

Thirty-one patients with hypothyroidism, 28 females age 47.5 ± 13.5 (mean ± SD) years and 3 males age 55.7 ± 11.2 years ingested the dose of l-T4 in 120 mL water containing or not containing 500 mg vitamin C in a solution of pH 2.9 ± 0.1 (mean ± SD). Serum concentrations of free T4 and TSH were measured at the end of 3 periods of 2 months each, 2 controls and 1 vitamin C. Serum total T3 was measured in 16 of the patients, before and at the end of the vitamin C period. Serum TSH and free T4 and T3 were measured by a solid-phase, enzyme-labeled chemiluminescent competitive immunoassay All patients had gastrointestinal pathology and were not in good control when taking l-T4 before the study, and 23 had autoimmune thyroiditis or idiopathic hypothyroidism. The median l-T4 dose was 100 μg with an interquartile range of 50 μg. The protocol was reviewed and approved by our institution's ethics committee. Patients were asked to sign a written consent to participate in the study.

RESULTS

Serum concentrations of TSH, free T4, and T3 improved while on vitamin C. Serum TSH decreased in all patients (control, 11.1 [10.5] μIU/mL, median [interquartile range]), vitamin C 4.2 (3.7) μIU/mL, P = .0001), and it was normalized in 17 patients (54.8%). The average decrease was 69.2%. Serum T4 was higher with vitamin C in 30 of the 31 patients (control, 1.1 [0.3] ng/dL; vitamin C, 1.3 [0.3] ng/dL; P < .0001), and serum T3 increased as well in all 16 patients in whom it was measured (control, 60.5 [16.5] ng/dL; vitamin C, 70 [21] ng/dL; P < .005).

CONCLUSIONS

In patients with hypothyroidism and gastrointestinal pathology, vitamin C improves the abnormalities in serum free T4, T3, and TSH concentrations. This approach is helpful in the management of these patients.

Perioperative management of a patient with thyroid hormone resistance who underwent total thyroidectomy for thyroid cancer

Resistance to thyroid hormone (RTH) is a rare, predominantly inherited syndrome that involves impaired tissue responsiveness to thyroid hormones. We describe the perioperative management of a patient with RTH who underwent total thyroidectomy. Although surgery performed under general anesthesia was uneventful, after the surgery the patient developed difficult-to-treat hypocalcemia that lasted until postoperative day 4. Moreover, thyroid function even after discharge remained unstable despite replacement therapy. We suggest that the parathyroid and thyroid function of patients with RTH be followed very closely and that nociceptive stimulus of the surgery and postoperative pain be reduced as much as possible.

[Therapeutic possibilities in patients with selective pituitary resistance to thyroid hormones]

Selective pituitary resistance to thyroid hormones (SPRTH) is a non-neoplastic form of inappropriate secretion of thyrotropin (TSH). The etiology of this hormonal resistance is linked to inactivating mutations in the thyroid hormone receptor beta (TR-beta) gene. These mutations affect critical portions of the receptor's triiodothyronine (T3)-binding domain. Clinically, SPRTH is characterized by hyperthyroidism with goiter and absence of pituitary mass in the morphologic study. Laboratory data show an elevation of free T3 and free thyroxine concentrations without suppression of TSH, with normal molar subunit alpha/TSH ratio. At this time, there is no specific therapy for SPRHT. Beta blockers, such as atenolol, and benzodiazepines have been used as a symptomatic therapy. Among the drugs with the capacity for reducing TSH secretion are TR agonists, such as triiodothyroacetic acid, D-thyroxine, triiodothyropropionic acid, and L-T3.

Resistance to thyroid hormone: report of 2 kindreds with 35 patients

OBJECTIVE

To report two kindreds with resistance to thyroid hormone (RTH), particularly the clinical and laboratory evolution after thyroidectomy and with antithyroid drug treatment.

METHODS

Clinical data and thyroid function were determined in 82 members from three different generations of both families. Unaffected relatives were used as a control group. Response of thyroid-stimulating hormone (TSH) to the hypothalamic thyrotropin-releasing hormone (TRH) was evaluated in five patients and compared with five nonaffected relatives.

RESULTS

Thirty-five (22 male and 13 female) patients had high serum levels of thyroxine and triiodothyronine in conjunction with nonsuppressed TSH. Goiter was present in 66% of affected family members; prevalence was 10% in childhood and 88% in adulthood. The prevalence of goiter was 18% in nonaffected relatives. No patient showed evidence of thyroid hypofunction or hyperfunction, and the TSH response to TRH was similar to that of nonaffected relatives. The incidence of RTH in offspring was 60%, consistent with autosomal dominant transmission. Four patients had undergone thyroidectomy, and two required a second operation because of recurrence of goiter. Patients who had undergone thyroidectomy had normal or near-normal levels of thyroid hormone and very high values of TSH despite thyroid hormone therapy. Five patients were treated with antithyroid drugs for 2 to 10 years, but their thyroid function remained similar to that of nontreated patients.

CONCLUSION

RTH is a relatively rare and benign condition that can be misdiagnosed as hyperthyroidism. The disease is responsible for a high prevalence of goiter in affected families. Thyroidectomy and treatment with antithyroid drugs are not indicated and may have lifelong implications.

Cardiac involvement in thyroid hormone resistance

To analyze the cardiovascular alterations thought to occur in resistance to thyroid hormone (RTH), cardiac involvement in 54 patients with RTH was investigated with the help of two-dimensional and Doppler echocardiography. Data from 41 of 54 adult subjects with RTH were also compared with those of 24 and 20 cases with hyperthyroidism (H) and hypothyroidism (h), respectively, as well as 22 healthy euthyroid controls (C). With respect to the type of mutations, no correlation was found between cardiovascular features and genotype. Compared with affected adults, children with RTH showed markedly higher serum free T3 (FT3), free T4 (FT4), and baseline TSH concentrations. Compared with healthy children of comparable age, RTH children had significantly higher heart rate and lower left ventricular (LV) ejection fraction (P = 0.006). Also, higher heart rate and FT4 as well as shorter diastolic relaxation of the myocardium (all P = 0.001) between RTH subjects with and without thyrotoxic cardiovascular features were found. Cardiac symptoms (palpitations, 32% vs. 71%) and signs (sinus tachycardia, 26% vs. 79%; atrial fibrillation, 6% vs. 17%) were significantly less frequent in RTH vs. H (all P = 0.001). Compared with C and h, heart rate, cardiac output, stroke volume, and systolic aortic flow velocity were strongly increased in RTH (all P = 0.0001) and H, although ejection (P = 0.0012) and shortening (P = 0.0001) fractions of the LV were markedly lower in RTH vs. H. Diastolic parameters, such as isovolumic relaxation (P = 0.0001) and deceleration time (P = 0.013), were shorter in RTH vs. h and C. In RTH, positive correlations between FT3 and heart rate, and between FT4 and LV ejection fraction were observed, whereas negative correlations between both FT3 and FT4 and isovolumic relaxation were noted. In conclusion, these findings indicate a modulated hyperthyroid effect on cardiac systolic and diastolic function of the myocardium in RTH, whereas other parameters, such as ejection and shortening fractions of the LV, systolic diameter, and LV wall thickness, were comparable to C. Differences in term of cardiovascular changes were smaller between the RTH and C groups than the RTH and the H or h groups. Thus, an incomplete cardiac response to thyroid hormone is present in RTH.

Generalized resistance to thyroid hormone associated with possible selective cardiac nonresistance

OBJECTIVE

To review the condition of generalized resistance to thyroid hormone and to report a case of generalized thyroid hormone resistance associated with atrial fibrillation.

METHODS

A case report is presented of a 52-year-old man with atrial fibrillation who was referred by a cardiologist for thyroid ablation because of "hyperthyroidism," when his free thyroxine was found to be 4.35 ng/dL (normal, 0.55 to 2.46) and his free triiodothyronine was 6.5 pg/mL (normal, 1.4 to 4.4).

RESULTS

This clinically euthyroid man with no signs or symptoms of hyperthyroidism except for the possibly related atrial fibrillation had a thyrotropin level of 3.45 mIU/L (normal, 0.46 to 4.7) in conjunction with the aforementioned increased levels of thyroid hormones. Further evaluation revealed normal 6-hour (11.7%) and 24-hour (27.6%) (123)I uptakes. Magnetic resonance imaging of the pituitary revealed a normal-sized gland with no masses.

CONCLUSION

This is a rare case of generalized resistance to thyroid hormone in a patient with only atrial fibrillation. Whether the heart was selectively nonresistant to thyroid hormone as the cause of his atrial fibrillation or whether his atrial fibrillation was due to his mitral valve prolapse documented on echocardiography could not be determined with certainty. His ventricular rate of 83 per minute and laboratory evaluation suggest that thyroid hormone was not the cause of the atrial fibrillation.

Increased levothyroxine requirements presenting as "inappropriate" TSH secretion syndrome in a patient with nephrotic syndrome

Patients with primary thyroid failure on levothyroxine (LT4) replacement who develop nephrotic syndrome (NS) may rarely present with an increase in LT4 requirements. In this report, we describe a patient with thyroid failure following radioactive iodine ablation for Graves' disease who required an escalation of LT4 doses following the onset of NS. The case presented with disproportionately elevated TSH levels in the presence of normal (or slightly subnormal) thyroid hormone levels, thus, masquerading as a state of "inappropriate" TSH secretion. This pattern of extreme dysregulation in thyroid function indices due to urinary loss of thyroid hormones has not been previously described in NS, and, therefore, extends the spectrum of endocrine manifestations of NS.

[Thyroid hormone resistance syndromes: clinical aspects]

INTRODUCTION

Syndromes of resistance to thyroid hormone correspond to variable clinical states which are usually transmitted as autosomal dominant traits and characterized by the lack of sensitivity of target tissues to triiodothyronine (T3). The diagnosis has to be performed in order to offer an appropriate therapy.

CURRENT KNOWLEDGE AND KEY POINTS

Clinical states range between two extremes: the generalized form, with global euthyroidism, and the predominantly pituitary form, with thyrotoxicosis. Surprisingly, these various clinical situations are usually determined by the same genetic defect, i.e., an anomaly of one of the two alleles of the gene encoding the thyroid hormone receptor TR beta. High levels of circulating thyroid hormones in the presence of detectable thyroid stimulating hormone (TSH) levels is the characteristic biological feature. Pituitary thyreotropic adenoma, another etiology of inappropriate secretion of TSH, needs thus to be ruled out. No treatment is required in case of generalized resistance to thyroid hormone, whereas two specific drugs (TRIAC and D-T4) appear to be useful in the predominantly pituitary form.

FUTURE PROSPECTS AND PROJECTS

Mechanisms of resistance have been well documented, therefore allowing better understanding of T3 action on its nuclear receptor. Several transcriptional cofactors or corepressors have been identified and have to be investigated to explain the intriguing inter- and intra-familial, and even intra-individual, phenotypic variability. New insights should, furthermore, be gained from these studies to precisely determine how therapeutic agents work in resistance to thyroid hormone.

Association of oestrogen receptor gene polymorphisms with outcome of ovarian stimulation in patients undergoing IVF

Oestrogen plays an important role in follicular formation and oocyte maturation via its receptor (ER). Many studies have shown association of the ER gene polymorphisms with a variety of pathological conditions. In this study we have examined the relationship of a common PvuII and a rare BstUI polymorphism in the ER gene to the mean numbers of follicles and oocytes, their mean ratios, mean number of embryos, mean oestrogen concentrations, mean size of the follicles and pregnancy rates. Analyses were carried out in 200 local Chinese patients undergoing in-vitro fertilization (IVF) and embryo transfer in three consecutive cycles. The mean follicular number, oocyte number, embryo number, follicular size and pregnancy rate were significantly smaller in patients homozygous for PvuII polymorphism (P < 0.001). These results indicate that PvuII polymorphism may be associated with ovarian follicular development and subsequently with the pregnancy rate. This study supports the view that genetic variability in the ER gene may have a role in the quality of the ovarian follicles in stimulation, which may affect implantation. However BstUI polymorphism was not found in either the IVF or control groups, suggesting that it has no role in the local Chinese population.

The Syndrome of Resistance to Thyroid Hormone, Misdiagnosed and Treated as Thyrotoxicosis

OBJECTIVE

To report two cases of resistance to thyroid hormone and to promote increased awareness of this syndrome, which is frequently misdiagnosed and incorrectly treated.

METHODS

We describe a young woman and her father, both of whom were diagnosed at a younger age as having thyrotoxicosis and were treated with thyroidectomy and radioactive iodine. Both patients later proved to have resistance to thyroid hormone and required supraphysiologic doses of levothyroxine to normalize the thyroid-stimulating hormone (TSH) while remaining euthyroid.

RESULTS

Laboratory evaluation revealed increased serum total thyroxine and triiodothyronine levels as well as normal to increased TSH levels. The free alpha sub-unit/TSH ratio was normal, and magnetic resonance imaging of the pituitary gland showed no tumor. Metabolic studies in the daughter, with use of graded doses of triiodothyronine, supported the diagnosis.

CONCLUSION

Both patients shown to have resistance to thyroid hormone were misdiagnosed and inappropriately treated in the past. The resultant hypothyroidism has been difficult to treat, particularly in the father who has coronary artery disease.

Peak oxygen uptake, muscle volume, and the growth hormone-insulin-like growth factor-I axis in adolescent males

PURPOSE

The growth effects of exercise appear to be mediated in part by central neuroendocrine control reflected in circulating levels of growth hormone (GH), insulin-like growth factor-I (IGF-I), and their binding proteins (BP). In previous studies positive correlations between peak VO2 and circulating IGF-I have been demonstrated. The relationship between peak oxygen uptake and these potential regulating factors has not been examined in adolescent males where patterns of GH pulsatility and levels of IGF-I are rapidly changing.

METHODS

Forty-three healthy adolescent males (age 16 +/- 0.7 yr, 70% at Tanner V) performed cycle ergometry to determine p oxygen uptake (peak VO2), and magnetic resonance images to determine the thigh muscle volume. Baseline blood samples were collected for GHBP, the extracellular portion of the GH tissue receptor (by ligand mediated immunofunctional assay), IGF-I (by RIA), and IGFBPs 1-5 (by RIA). Mean GH was determined from samples obtained every 20 min overnight.

RESULTS

Peak VO2/kg was positively correlated with mean overnight GH levels (r = 0.41, P < 0.005). Both peak VO2/kg and thigh muscle volume/kg were negatively correlated with GHBP (r = -0.33, P < 0.02) and IGFBP-4 (r = -0.52, P < 0.005). There were no correlations between peak VO2/kg and IGF-I or IGFBPs 1-3, and 5.

CONCLUSIONS

GH pulsatility is increased adolescent males who have higher peak VO2, but this did not translate into increases in IGF-I. We speculate that in the fitter males, lower GHBP levels may reduce hepatic sensitivity to GH. Thus, circulating IGF-I was unchanged despite higher mean GH in subjects with higher peak VO2. IGFBP-4 which is known to inhibit IGF-I was negatively correlated with peak VO2 leading, possibly, to increased IGF-I bioactivity. Fitness (as assessed by muscle mass and peak VO2) does modulate the GH-IGF-I axis, but not solely through circulating IGF-I; both GHBP and IGFBPs play important roles.

Detection of a new de novo mutation at codon 251 of exon 8 of thyroid hormone receptor beta gene in an Italian kindred with resistance to thyroid hormone

Resistance to thyroid hormone (RTH) is almost invariably associated with mutations of the thyroid hormone (TH) receptor beta (hTR beta) gene and is inherited as an autosomal dominant disease. Mutations of hTR beta identified in patients affected by RTH cluster generally at two spots of the ligand binding domain. We investigated whether an Italian kindred with RTH had a mutation in the thyroid hormone (TH) receptor beta gene. Blood samples were obtained from the available family members for biochemical and genetic analyses. Thyroid function tests in basal conditions, and in the case of the propositus also following incremental doses of T3, were performed. Exon 4 to 10 of hTR beta gene were amplified using the polymerase chain reaction (PCR) and the mutation was identified by direct sequence analysis. The affinity constant of this mutated receptor for T3 was measured by in vitro transcription-translation and was then compared with that of wild type. We identified a heterozygous G to A transition at nucleotide 1037 of exon 8 at codon 251, resulting in a glycine (G) to glutamic acid (E) substitution (G251E) in the patient affected by RTH and in his affected offspring, but not in the normal family members. This novel mutation represents a de novo mutation since both parents of the index case were unaffected and did not have this genomic mutation. When expressed in vitro, the mutant protein (G251E) showed a marked decrease of the affinity for T3, suggesting an impaired ligand-dependent transactivation activity of this mutant receptor. In vivo studies with incremental doses of L-T3 demonstrated a reduced sensitivity to TH in the index case, in particular at the pituitary level where the thyrotrophs' activity was not completely inhibited even by 200 micrograms/day of L-T3. G251E mutation represents the fourth mutation described up to now in exon 8 of hTR beta among the subjects affected by RTH. A third cluster of mutations of the c-erbA beta gene located proximally with respect to the other two so far described begins to emerge in RTH patients.

Management of hypothyroidism during pregnancy

Hypothyroidism during pregnancy occurs in 1/1600-2000 deliveries, according to the most recent publications. The most common causes are chronic autoimmune thyroid disease, radiodine-131 treatment, or surgical removal. The diagnosis is difficult to make on clinical grounds alone, even in advanced cases, and a high index of suspicion is needed. Some women are at high risk of developing hypothyroidism, and they should be screened. These women may have had previous treatment for hyperthyroidism; high-dose neck irradiation, evidence of thyroid autoimmunity, amiodarone therapy, suspected hypopituitarism, and type I diabetics. The best laboratory test is the serum TSH, followed, if elevated, by a free T4 index and a TPO-ab titer. Thyroid antibodies have been associated with an increased (double) risk of miscarriage and postpartum thyroiditis. Frequent (22-44%) pregnancy-induced hypertension leading to preterm delivery, and prematurity is the main complication observed in those still hypothyroid near term. Proper therapy eliminates or reduces the risk. No congenital anomalies have been reported in the most recent studies, and the data available shows that both physical and mental development have been normal until children are 10 years old. However, one study reported lower IQs in children of euthyroid women with positive TPO-ab than in children of TPO-ab negative mothers. Levothyroxine is the treatment of choice. Euthyroidism must be reached and maintained in a timely fashion. Many women need more thyroxine during pregnancy, and surveillance of thyroid function is needed throughout gestation to make dose adjustments when needed. During the postpartum periods the thyroxine requirements decrease to preconception levels.

Treatment of pituitary resistance to thyroid hormone (PRTH) in an 8-year-old boy

We report on an 8-year-old boy with pituitary resistance to thyroid hormone (PRTH) having a cysteine for arginine substitution at codon 320 in the TR-beta gene who was presented because of thyrotoxicosis. Due to its suppressive effect on the pituitary thyrotropin secretion, treatment with D-thyroxine (D-T4) was started. After a few days, clinical euthyroidism was achieved but thyroid stimulating hormone secretion was not suppressed. Symptoms of thyrotoxicosis relapsed when therapy was interrupted so that therapy with D-T4 was reinstituted and continued to date. Symptoms did not recur, and the psychomotor development proceeded normally. D-T4 should therefore be considered in the treatment of thyrotoxicosis in PRTH.

Phenotypic variability in patients with generalised resistance to thyroid hormone

Genetic linkage of generalised resistance to thyroid hormone (GRTH) to the human thyroid receptor beta 1 gene has been identified. To date 38 different mutations in several kindreds have been documented. We report on a family with GRTH displaying an adenine for guanine substitution at nucleotide 1234 resulting in a threonine for alanine substitution at codon 317 of exon 9. This mutation has been described for different phenotypes, suggesting that the heterogeneity in GRTH may be the result of multiple genetic factors.

Estrogen resistance caused by a mutation in the estrogen-receptor gene in a man

BACKGROUND AND METHODS

Mutations in the estrogen-receptor gene have been thought to be lethal. A 28-year-old man whose estrogen resistance was caused by a disruptive mutation in the estrogen-receptor gene underwent studies of pituitary-gonadal function and bone density and received transdermal estrogen for six months. Estrogen-receptor DNA, extracted from lymphocytes, was evaluated by analysis of single-strand-conformation polymorphisms and by direct sequencing.

RESULTS

The patient was tall (204 cm [80.3 in.]) and had incomplete epiphyseal closure, with a history of continued linear growth into adulthood despite otherwise normal pubertal development. He was normally masculinized and had bilateral axillary acanthosis nigricans. Serum estradiol and estrone concentrations were elevated, and serum testosterone concentrations were normal. Serum follicle-stimulating hormone and luteinizing hormone concentrations were increased. Glucose tolerance was impaired, and hyperinsulinemia was present. The bone mineral density of the lumbar spine was 0.745 g per square centimeter, 3.1 SD below the mean for age-matched normal women; there was biochemical evidence of increased bone turnover. The patient had no detectable response to estrogen administration, despite a 10-fold increase in the serum free estradiol concentration. Conformation analysis of his estrogen-receptor gene revealed a variant banding pattern in exon 2. Direct sequencing of exon 2 revealed a cytosine-to-thymine transition at codon 157 of both alleles, resulting in a premature stop codon. The patient's parents were heterozygous carriers of this mutation, and pedigree analysis revealed consanguinity.

CONCLUSIONS

Disruption of the estrogen receptor in humans need not be lethal. Estrogen is important for bone maturation and mineralization in men as well as women.

Characterization of estrogen receptor cDNAs from human uterus: identification of a novel PvuII polymorphism

Using reverse transcription and the polymerase chain reaction, we have cloned estrogen receptor complementary DNAs from normal human uterine tissue. Restriction endonuclease analysis identified a polymorphic PvuII recognition site within half of the receptor cDNAs. Sequence analysis revealed a number of differences with the sequence previously reported for the ER cDNA isolated from MCF7 cells and confirmed that the codon for amino acid 400 was erroneously assigned as valine (GTG) rather than glycine (GGG). Sequencing also defined the nature of the PvuII polymorphism, with allele A coding for Glu22 and allele B (with an additional PvuII site) coding for Gln22. We demonstrate that both alleles of this receptor activate transcription of an estrogen-responsive gene to the same extent. This selective cloning method should have wide application in the investigation of naturally occurring cDNA variants from diseased tissues, such as breast cancer cell lines and primary tumor specimens.