Matthew D. Ringel

Expression of the Sodium Iodide Symporter and Thyroglobulin Genes Are Reduced in Papillary Thyroid Cancer

Altered expression of the gene encoding the sodium iodine symporter (NIS) may be an important factor that leads to the reduced iodine accumulation characteristic of most benign and malignant thyroid nodules. Both up- and down-regulation of NIS gene expression have been reported in thyroid cancer using several different methods. The goal of the present study was to accurately identify alterations in NIS gene expression in benign and malignant thyroid nodules using an accurate real-time quantitative RT-PCR assay system. Total RNA was prepared from 18 benign thyroid nodules, 20 papillary thyroid cancers, and 23 normal thyroid samples from 38 subjects. Quantitative RT-PCR was used to measure NIS and thyroglobulin (TG) mRNA expression in normal thyroid tissue and in each nodular tissue sample. Papillary thyroid cancer samples had significantly lower NIS mRNA expression (72 ± 41 picogram equivalents [pg Eq]), than did benign nodules (829 ± 385 pg Eq), or normal tissues (1907 ± 868 pg Eq, P = 0.04). Most important, in the paired samples, NIS gene expression was decreased in each papillary thyroid cancer compared with normal tissue (69% median decrease; range, 40–96%; P = .013). Eleven of the 12 benign nodules also demonstrated lower NIS gene expression than the normal tissue (49% decrease; range, 2–96%; P = .04). Analysis of the paired samples demonstrated that Tg mRNA expression was significantly lower in each of the thyroid cancer samples than in corresponding normal tissue (759 ± 245 pg Eq vs. 1854 ± 542 pg Eq, P = .03). We have demonstrated a significant decrement in NIS gene expression in all papillary thyroid cancers and in over 90% of benign nodules examined compared with adjacent normal thyroid tissue, using a highly accurate quantitative RT-PCR technique. Similarly, thyroid cancers demonstrated significantly lower TG mRNA expression than corresponding normal thyroid. Reduced NIS expression may be an important factor in the impairment of iodine-concentrating ability of neoplastic thyroid tissues.

Akt Controls Vascular Smooth Muscle Cell Proliferation In Vitro and In Vivo by Delaying G1/S Exit

Abstract— Constitutive activation of serine/threonine kinase Akt causes uncontrolled cell-cycle progression in different cell types and in malignancy. To investigate how Akt activation modulates cell-cycle progression in vascular smooth muscle cells (SMCs) in vitro and in the intact animal, we inhibited Akt-dependent signaling by adenovirus-mediated transfection of a dominant-negative Akt mutant (AA-Akt). We observed reduced proliferation rate (P <0.01), DNA synthesis (P <0.01), and a significant arrest in G1/S exit (P <0.01) both in vitro in response to serum stimulation and in vivo after vascular injury. In vivo transfection of the balloon-injured vessel with AA-Akt reduced SMC proliferation, resulting in decreased neointima compared with control virus (P <0.01). These effects were at least in part modulated, both in vitro and in vivo, by increased p21Cip1 expression, as demonstrated by lack of effect of AA-Akt on cell proliferation in p21−/− mouse SMCs. In conclusion, this study demonstrates that Akt-dependent signaling enhances cell-cycle progression of nontransformed SMCs in vitro and in response to vascular injury in the intact animal. These results suggest a role for Akt signaling in modulating the response of normal tissues to stress and the response of the arterial wall to acute and possibly repetitive injuries that ultimately contribute to restenosis and atherosclerosis.

Papillary and follicular variant of papillary carcinoma of the thyroid: Initial presentation and response to therapy

INTRODUCTION : The 2 most common histologic variants of papillary carcinoma are pure papillary carcinoma (PTC) and follicular variant of papillary thyroid carcinoma (FVPTC). The purpose of this study is to compare the presentation and short-term response to therapy of these variants and to determine if FVPTC is a more aggressive form of thyroid cancer that warrants intensive therapy. METHODS : A retrospective chart review of patients treated for PTC and FVPTC between 1996 and 1999 was performed. Clinical variables were compared with the Wilcoxon Rank-Sum test or the Fischers Exact Test. RESULTS : Of 160 patients with papillary thyroid carcinoma included, 114 (71%) had PTC and 46 (29%) had FVPTC. Mean follow-up was 38.6 months. FVPTC presented with larger tumors (median 1.5 cm vs 1.0 cm, P = 0.007) and higher tumor stage than PTC. PTC patients were more likely to present with local invasion and to have local recurrence (9.65% vs 0% for both variables). There were no significant differences in patient age, gender, vascular invasion, lymph node or distant metastases, surgical treatment, radioactive iodine therapy, remission, or mortality. CONCLUSION : FVPTC presented with larger original tumor size and higher tumor stage but a lower local invasion rate and recurrence rate than patients with PTC despite similar therapies. These data suggest that FVPTC and PTC carry similar prognoses in early stages and that FVPTC may have a reduced predilection for local invasion. Although further studies with longer follow-up are required, these results do not suggest that FVPTC warrants more aggressive therapy than PTC.

Measurement of thyroglobulin mRNA in peripheral blood as an adjunctive test for monitoring thyroid cancer

Aims: Monitoring treated patients with thyroid cancer for recurrent or metastatic disease is currently based upon the serial measurement of circulating plasma thyroglobulin (Tg) concentrations. However, the clinical usefulness of Tg immunoassays is limited by poor sensitivity and interference from anti-Tg antibodies. This study investigated whether the detection of Tg mRNA in peripheral blood, using reverse transcriptase polymerase chain reaction (RT-PCR), is of value in the biochemical surveillance of patients with thyroid cancer. Methods: RNA was extracted from peripheral blood of five normal controls, six patients with abnormal thyroid function tests, and 28 patients who had undergone thyroidectomy for well differentiated thyroid cancer. From each, an 87 bp product from base pair 262 to 348 in the cDNA sequence of the thyroglobulin gene was amplified by RT-PCR. Results: Tg mRNA was detected in normal individuals and patients with thyroid cancer. In the group of patients studied, identification of metastatic thyroid tissue by radioiodine scanning correlated better with Tg mRNA assay results than with serum Tg concentrations (accuracy 84% v 75%). No interference from circulating Tg antibodies was apparent. In patients studied prospectively over a 12 month period, there was a significant correlation between detectable Tg mRNA in peripheral blood and the presence or absence of metastatic disease, as demonstrated by radioiodine scanning. Conclusions: These results suggest that detection of Tg mRNA in blood is a more sensitive marker for metastatic thyroid disease than Tg immunoassay, and appears to be unaffected by the presence of circulating anti-Tg antibodies.

Epidermal growth factor inhibition of c-Myc-mediated apoptosis through Akt and Erk involves Bcl-xL upregulation in mammary epithelial cells

In earlier studies, we and others have established that activation of EGFR can promote survival in association with upregulation of Bcl-x(L). However, the mechanism responsible for upregulation of Bcl-x(L) is unknown. For the current studies we have chosen pro-apoptotic, c-Myc-overexpressing murine mammary epithelial cells (MMECs) derived from MMTV-c-Myc transgenic mouse tumors. We now demonstrate that EGFR activation promotes survival through Akt and Erk1/2. Blockade of EGFR kinase activity and the PI3-K/Akt and MEK/Erk pathways with pharmacological inhibitors resulted in a significant induction of cellular apoptosis, paralleled by a downregulation of both Akt and Erk1/2 proteins. Consistent with a survival-promoting role of Akt, we observed that constitutively activated Akt (Myr-Akt) inhibited apoptosis of pro-apoptotic, c-Myc-overexpressing cells following the inhibition of EGFR tyrosine kinase activity. In addressing possible downstream effectors of EGFR through activated Akt, we detected significant upregulation of Bcl-x(L) protein, suggesting this pro-survival protein is a target of Akt in MMECs. By using pharmacological inhibitors of PI3-K/Akt and MEK/Erk together with dominant-negative Akt and Erk1 we observed the decrease in Bcl-x(L) protein. Our findings may be of importance for understanding the emerging role of Bcl-x(L) as a potential marker of poor prognosis in breast cancer.

Evaluation of adult papillary thyroid carcinomas by comparative genomic hybridization and microsatellite instability analysis

To clarify the mechanism of tumorigenesis in papillary thyroid carcinoma (PTC) and ascertain whether genomic changes correlate with histologic features, we conducted a comprehensive molecular evaluation of PTC using comparative genomic hybridization (CGH) and microsatellite instability (MSI) analysis in a set of 17 histologically well-characterized PTC specimens. To our knowledge, this is the first study that evaluates chromosomal and nucleotide instability in the same PTC tumor specimens. Four of 15 samples (27%) had aberrations detected by CGH. All four had a partial or complete gain of chromosome 20, and 3 of 4 had a partial or complete loss of chromosome 13. No MSI was detected in any of the PTC samples (n=16), and all samples examined by immunohistochemistry (n=9) expressed the DNA repair enzymes hmlh1 and hmsh2. All PTC samples with abnormal CGH had vascular invasion or invasion of the thyroid capsule, and there was a significant correlation between the presence of chromosomal aberrations and capsular/vascular invasion (P=0.026). We conclude that although chromosomal and microsatellite instability are uncommon in PTC, tumors with chromosomal aberrations are more likely to be associated with invasion.

Current Therapy for Childhood Thyroid Cancer: Optimal Surgery and the Legacy of King Pyrrhus

Follicular cell-derived thyroid cancer is far less common in children than adults and accounts for approximately 1% of all pediatric malignancies. Compared with adults, children and adolescents with differentiated papillary and follicular thyroid cancer are more likely to have advanced or multicentric disease and metastatic dissemination of cancer to regional lymph nodes and distant tissues at the time of initial diagnosis. Cancer recurrence is also more common in children with differentiated thyroid cancer (DTC) than in adults. On the other hand, despite the advanced stage of their cancers, children and adolescents with DTC have an excellent prognosis and enjoy very low mortality rates. This striking dissonance suggests that late diagnosis rather than aggressive behavior may account for the more extensive disease at presentation. Still, there may be fundamental differences in the biology of childhood and adult thyroid cancer that have potentially important clinical implications. For example, the juvenile thyroid gland exhibits enhanced sensitivity to radiation-induced genetic change and neoplasia, which could relate to the increased propensity to multicentric disease. Nikiforov et al.1 demonstrated that approximately 70% of pediatric papillary thyroid cancers contained RET/PTC oncogene rearrangements regardless of a history of radiation exposure. By contrast, only 20% of sporadic adult papillary cancers contain a RET/PTC rearrangement.2 Regardless of patient age, management of DTC generally includes surgery, total thyroidectomy if the tumors are larger than 1.5 cm or metastases are detected, and resection of enlarged cervical lymph nodes. Surgery is generally followed by administration of radioactive iodine to eradicate any remaining normal and malignant thyroid tissue. After this initial ablative therapy, patients are treated with supraphysiological doses of L-thyroxine to suppress pituitary secretion of thyrotropin, a trophic hormone that can promote growth of thyroid cancer cells. Patients are subsequently monitored to detect any evidence of recurrence or progression of thyroid cancer, most commonly by whole body iodine-131 (I) scintigraphy and measurement of serum levels of thyroglobulin after administration of recombinant thyrotropin or after induction of hypothyroidism via withdrawal of L-thyroxine therapy. In selected patients additional tests might include ultrasound examination of the neck or magnetic resonance imaging, computed tomography, and positron emission tomography scans. Recurrent or persistent cancer is then treated with additional surgery, radioactive iodine, or external beam radiation, either alone or in combination. Do the available data support aggressive initial surgery in the management of childhood DTC? Are the benefits worth the risks of permanent hypothyroidism and laryngeal nerve dysfunction? Exchange scalpel for sword, and the exploits of Pyrrhus, the courageous if imprudent warrior king of the Hellenistic kingdom of Epirus, come to mind. In 281 BC, Pyrrhus assembled an army of 25,000 men and 20 elephants to march against Rome and establish a kingdom of Sicily and lower Italy. Although successful, his many battles were so costly that he was forced to withdraw from Italy, remarking, “Another such victory and I shall be ruined.” By analogy, clinicians must ask whether our surgical victories over thyroid cancer come at too great a morbidity. A conclusive answer is not yet available, and the impact of initial surgical therapy on outcome in patients with DTC continues to be a very controversial topic. Management of adult patients with DTC is based on the results of large, Received November 1, 2002; accepted November 8, 2002. From the Section of Endocrinology (MDR), Washington Hospital Center/MedStar Research Institute, Washington, DC; and the Division of Pediatric Endocrinology (MAL), Johns Hopkins University School of Medicine, Baltimore, Maryland. Address correspondence to: Michael A. Levine, MD, Division of Pediatric Endocrinology, Johns Hopkins University School of Medicine, 211 Park Building, 600 N. Wolfe St., Baltimore, MD 21287; Fax: 410-955-9773; E-mail: mlevine@jhmi.edu.

Clinical Aspects of Miscellaneous and Unusual Types of Thyroid Cancers

The majority of epithelial thyroid tumors maintain some degree of thyroid follicular cell function, as evidenced by thyroglobulin production and the ability to concentrate iodine. They also have typical histological appearances, such as those seen in papillary and follicular carcinomas In this chapter we discuss a group of unusual primary thyroid neoplasms characterized by limited or absence of differentiated thyroid cellular function and structure; they have, in general, more aggressive clinical courses than differentiated carcinomas We also discuss tumors that metastasize to the thyroid gland. These thyroid tumors have been classified by the World Health Organization (WHO) under the headings of “other” thyroid carcinomas, nonepithelial tumors, and in the case of several histological types to be discussed, variants of papillary and follicular carcinoma (1,2).

Therapy of Graves’ Ophthalmopathy

As described in Chapter 18, the characteristic ophthalmopathy of Graves’ disease is marked by impaired eye muscle movement, periorbital edema, with or without actual proptosis. The exophthalmos may be unilateral early but usually becomes bilateral with time. With moderate to advancing severity, the proptosis will be accompanied by varying degrees of ophthalmoplegia and congestive oculopathy characterized by Chemosis, conjunctivitis, and periorbital swelling. The most dreaded potential complications are corneal ulceration, optic neuritis, and optic atrophy. When exophthalmos becomes more severe and progresses rapidly to this point, it has been termed “malignant exophthalmos”. The term exophthalmic ophthalmoplegia refers to the ocular muscle weakness that results in impaired upward gaze and convergence and strabismus with varying degrees of diplopia. Progressive ophthalmopathy is the most difficult component of Graves’ disease to treat successfully. Given four fixed bony orbital walls, the increased intraorbital contents (enlarged external ocular muscles due to lymphocytic infiltration and edema, increased retrobulbar fat) cause the globe to protrude outward causing proptosis. With limits to outward proptosis, pressure can be directed posteriorly on the optic nerve in its course between the bodies of the eye muscles causing ischemia and blindness. In its later stages, the external eye muscles and the levator palpebrae become fibrotic with resultant restricted movement leading to blurred vision, diplopia, and lid retraction. A consequence of lid retraction may be corneal drying and exposure keratitis and ulceration.