Correction to: Hip fracture trends in the United States, 2002 to 2015

The name of the first author, E.M. Lewiecki, was rendered incorrectly in the original publication. The publisher regrets any inconvenience and is pleased to correct the error here.

Hip fracture trends in the United States, 2002 to 2015

An analysis of United States (US) Medicare claims data from 2002 to 2015 for women aged ≥ 65 years found that age-adjusted hip fracture rates for 2013, 2014, and 2015 were higher than projected, resulting in an estimated increase of more than 11,000 hip fractures.

INTRODUCTION

Hip fractures are a major public health concern due to high morbidity, mortality, and healthcare expenses. Previous studies have reported a decrease in the annual incidence of hip fractures in the US beginning in 1995, coincident with the introduction of modern diagnostic tools and therapeutic agents for osteoporosis. In recent years, there has been less bone density testing and fewer prescriptions for osteoporosis treatments. The large osteoporosis treatment gap raises concern of possible adverse effects on hip fracture rates.

METHODS

We assessed hip fracture incidence in the US to determine if the previous decline in hip fracture incidence continued. Using 2002 to 2015 Medicare Part A and Part B claims for women ≥ 65 years old, we calculated age-adjusted hip fracture rates, weighting to the 2014 population.

RESULTS

We found that hip fracture rates declined each year from 2002 to 2012 and then plateaued at levels higher than projected for years 2013, 2014, and 2015.

CONCLUSIONS

The plateau in age-adjusted hip fracture incidence rate resulted in more than 11,000 additional estimated hip fractures over the time periods 2013, 2014, and 2015. We recommend further study to assess all factors contributing to this remarkable change in hip fracture rate and to develop strategies to reduce the osteoporosis treatment gap.

Inhibition of growth hormone receptor activation by pegvisomant may increase bone density in acromegaly

Treatment of acromegaly with pegvisomant lowers serum IGF-1 and raises serum growth hormone. As both IGF-1 and GH are important for bone growth and remodeling, we were concerned that lowering of IGF-1 could cause loss of bone. To evaluate the effects of treatment of acromegaly with pegvisomant on bone mineral density (BMD) we developed an observational, prospective study. 7 acromegaly patients participated in the study. Male and female subjects aged 18 years or more were eligible to participate. Patients were eugonadal or on adequate gonadal replacement therapy for at least 3 years before participating in the study. These patients were treated with a mean dosage of 20 mg of pegvisomant daily for up to 7 years. Bone mineral density (BMD) was evaluated by dual X-ray absorbtiometry (DXA) at baseline, 8, and 18 months as a part of a prospective trial and periodically thereafter. Baseline mean serum insulin-like growth factor-1 (IGF-1) concentration±SD was elevated in all patients (679.86±138.21 ng/ml). The IGF-1 concentrations at 18 months decreased significantly from baseline (p=0.016). Wilcoxon signed-rank tests showed significant increases in the spine BMD from baseline to 18 months (p=0.016) and significant increases in the right hip BMD from baseline to 18 months (p=0.032). The range of the increases was 4.3-17.8% at 7 years. It is concluded that successful treatment of acromegaly with pegvisomant increases BMD.

Beyond RET: potential therapeutic approaches for advanced and metastatic medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is a rare calcitonin-producing neuroendocrine tumour that originates from the parafollicular C-cells of the thyroid gland. The RET proto-oncogene encodes the RET receptor tyrosine kinase, which has essential roles in cell survival, differentiation and proliferation. Activating mutations of RET are associated with the pathogenesis of MTC and have been demonstrated in nearly all hereditary and in 30-50% of sporadic MTC cases, making this receptor an excellent target for small-molecule inhibitors for this tumour. Clinical trials of small organic inhibitors of tyrosine kinase receptors (TKIs) targeting the RET receptor have shown efficacy for treatment of metastatic MTC with 30-50% of patients responding to these agents. Despite the importance of the RET receptor in MTC, it is clear that other signal transduction pathways, tyrosine kinase receptors, and tumour suppressor genes are involved in MTC tumourigenesis and progression. A better understanding of molecular cross-talk between these signal pathways and the RET receptor may lead to combinatorial therapy that will improve outcomes beyond what is currently possible with RET-directed TKIs. Finally, there is evidence that immunological-based therapy using dendritic cell vaccination strategies have been effective for reducing tumour mass in a small number of patients. The identification of additional MTC-specific tumour antigens and a better understanding of specific epitopes in these tumour antigens may lead to improvement of response rates.

Vandetanib in metastatic hereditary medullary thyroid cancer: Follow-up results of an open-label phase II trial

6018

Background: Medullary thyroid cancer (MTC) is the most common cause of death in patients with hereditary syndromes caused by activating mutations in the RET protooncogene. RET activation is the initial oncogenic event, with the activity of other receptor tyrosine kinases, including VEGFR and EGFR, likely to contribute to tumor growth and metastasis. Vandetanib (ZD6474) is a once- daily oral agent that selectively targets RET, VEGFR and EGFR tyrosine kinases. Methods: Eligible patients had unresectable, measurable, locally advanced or metastatic hereditary MTC and a RET germline mutation. Patients received vandetanib 300 mg/day until disease progression or any other withdrawal criteria. The primary objective was to assess the objective tumor response (RECIST every 3 months). Secondary assessments included disease control rate, biochemical response (determined by decrements in plasma levels of calcitonin, a tumor marker for MTC) and safety and tolerability. Results: Thirty patients (21 female; median age 50 years) received initial treatment with vandetanib 300 mg. At data cut-off (20 Nov 2006), the median duration of treatment was 172 days. Based on site investigator assessments, 20% (6/30) of patients experienced a partial response (duration of response 59–260 days) and another 30% (9/30) of patients experienced stable disease =24 weeks, yielding a disease control rate of 50% (15/30). Centralized independent confirmation of response is planned. In 19 patients, plasma calcitonin levels showed a =50% decrease from baseline that was maintained for at least 6 weeks. Adverse events (AEs) occurring in >50% of patients were rash (73%), diarrhea (67%), fatigue (57%) and nausea (53%). Most AEs were grade 1 or 2; grade 3 AEs included asymptomatic QTc prolongation (n=5), rash and diarrhea (both n=3), all of which were manageable. Conclusions: Vandetanib has demonstrated clinical activity in this phase II study in metastatic hereditary MTC, and the safety profile is generally consistent with previous vandetanib monotherapy studies. Accrual is now complete (30 patients), and an updated analysis will be performed in April 2007. An international, randomized, placebo-controlled phase II trial of vandetanib in MTC is now recruiting patients. #

No significant financial relationships to disclose.

Osteonecrosis of the jaw: Long-term follow-up shows variable rate of healing

9061

Background: Osteonecrosis of the jaw (ONJ) is a rare but clinically significant disorder recently reviewed in a large retrospective study (Hoff et al, 42nd ASCO Annual Meeting 2006, Abstract #8528). A subset of the ONJ patients from that study with breast cancer or multiple myeloma (MM) was followed at the University of Texas M.D. Anderson Cancer Center (UTMDACC) dental clinic. This analysis describes the natural history of ONJ in this subset. Methods: Thirteen of 29 ONJ patients treated with intravenous bisphosphonates (IVBP) at UTMDACC and 1 treated elsewhere were evaluated in the dental clinic for > 6 months (MM, n=7; breast cancer, n=7). The maximum length of exposed bone was measured at each visit. Patients received a standard regimen of conservative dental care with debridement when indicated. Results: All 14 patients received zoledronic acid (median cumulative dose 72 mg; range 24–152) and 10 also received pamidronate (median cumulative dose 1,710 mg; range 90–2,700). They were followed for a median duration of 17.1 months (range: 7.1–67.3). The mean length of exposed bone at initial evaluation was 11 mm (SD: 8.4). Each patient demonstrated fluctuating clinical courses. The lesion from baseline to the last visit progressed in 7 patients (median increase of 13 mm), remained stable in 2, regressed in 2 and resolved in 3. Persistent ONJ was seen if IVBP was stopped (n=8), decreased in frequency (n=1) or continued at the same dose/frequency (n=2). Complete resolution occurred in 3 MM patients, where IVBP was discontinued, decreased in frequency or replaced by weekly oral alendronate. Conclusions: Our experience shows that ONJ resolved in 21% but persisted in the majority of patients with a duration of up to 5 years with conservative dental care. Further studies are needed to evaluate the pathogenesis and healing process of ONJ.

No significant financial relationships to disclose.

Osteonecrosis of the jaw in patients receiving intravenous bisphosphonate therapy

8528

There have been reports of osteonecrosis of the jaw (ONJ) in patients (pts) with metastatic bone disease (MBD) treated with IV bisphosphonates (IVBP). To estimate the frequency and identify risk factors for ONJ we performed a retrospective analysis of pts treated with IVBP. The cohort included 4019 patients identified through the MDACC pharmacy database (PD) treated with IVBP from 9/1996 to 2/2004, and 6 patients diagnosed with ONJ at the MDACC Dental Clinic. ONJ was defined as exposed non-healing bone of at least 3 months duration. Preliminary statistical analysis included 4000 patients. The most common diagnoses were breast cancer [BRCA] (1340), MM (550) and lung cancer (380).The indications for IVBP therapy included MBD (60%), hypercalcemia (25%), MM (14%) and osteoporosis (7%). We identified 34 patients with ONJ: 18 BRCA, 14 MM, 1 prostate cancer and 1 thyroid cancer. The frequency of ONJ was calculated by including patients from the PD only: 16/1338 (1.2 %) in BRCA and 14/448 (3.1%) in MM. Patients with ONJ received pamidronate [P] (6), zoledronate [Z] (10), combination of P and Z (15). The mean cumulative dose (MCD) of P was 2182 mg (720–4410) in MM and 2745mg (1980–3510) in BRCA. MCD of Z was 61 mg (24–152) in MM and 62 mg (28–110) in BRCA. The total doses of P and Z were significantly higher in the ONJ group VS NON-ONJ group (P<0.0001). Pts with ONJ had longer duration of disease and longer follow-up than NON-ONJ cases (P<0.0001). Univariate and multivariate logistic regression analyses (MLRA) revealed dental extractions (DE), ER positive tumors, and treatments with P and Z as significant factors associated with ONJ in BRCA pts. In MM, DE, periodontal disease and osteoporosis were significant factors. Further statistical analysis, including Cox regression analysis, is under way. ONJ pts were treated with aggressive oral hygiene, oral rinses, debridement of necrotic bone and antibiotics. 15 pts were followed at the dental clinic longer than 6 months. ONJ healed in 1, improved in 1, stable in 4 and progressed in 9 pts. In conclusion, ONJ is a significant but uncommon event. Higher doses of IVBP, longer treatment duration, DE, and periodontal disease are associated with a greater risk to develop ONJ. Good dental care and avoidance of dental interventions should be recommended to all patients treated with IVBP.

[Table: see text]

Phase I/II trial of capecitabine (C), dacarbazine (D) and imatinib (I) (CDI) for patients (pts) metastatic medullary thyroid carcinomas (MTC)

13048

Background: MTC is a rare tumor that responds poorly to conventional chemotherapy. 5-FU and D are frequently used, with an expected response rate of around 15%. MTC is often associated with multiple endocrine neoplasia type 2, an autosomal dominant syndrome caused by a mutation in the RET proto-oncogene which encodes RET, a tyrosine kinase receptor. I is a tyrosine kinase inhibitor with activity against c-Kit, PDGF and possibly RET, and we postulated that its addition to chemotherapy would increase its efficacy against this disease. Methods: We designed a phase I/II trial combining escalating doses of oral C, IV D and oral I. Pts with any advanced solid tumors were eligible for the phase I part of the trial. Results: 13 pts were entered and 12 were eligible (7 MTC, 2 adrenocortical, 1 islet-cell, 1 insular thyroid and 1 small cell). 4 pts did not complete one cycle (1 pt withdrew after 5 days and 2 pts progressed in less than 10 days and were replaced for toxicity analysis, 1 had a DLT and is included). 3 patients were entered in dose level 1, without DLT. 2 out of 6 pts developed DLT at the second dose level (1 G 3 fatigue and 1 G3 hypokalemia). Three additional pts are being entered on dose level 1. The first one had PD after 7 days and is being replaced. For the 11 pts who were evaluable, best response was 3 SD (range 3 to 9 + months) and 8 PD. Conclusions: The combination of CDI is feasible but has resulted in an unexpected pattern of toxicity in this patient population, with fatigue and hypokalemia as the DLT. No significant diarrhea or hand-foot syndrome was seen. Only G1 and 2 fluid retention and neutropenia have been encountered. Only minor reduction in tumor size has been seen among these heavily pretreated pts. Once the phase I is complete, the trial will continue in a phase II setting for untreated MTC pts.

[Table: see text]

[Table: see text]

Limitations of size as a criterion in evaluating adrenal tumours

Background

Size is considered the single best predictor of malignancy in evaluating adrenal neoplasms identified incidentally during abdominal imaging, yet small adrenal cortical cancers have been reported previously from several centres.

Methods

This was a retrospective evaluation of the value of tumour size and other preoperative clinical parameters in predicting the presence or absence of malignancy in adult patients who underwent adrenalectomy for an adrenal tumour at this institution.

Results

One hundred and sixteen patients underwent adrenalectomy. Diagnoses were adrenal cortical carcinoma (n = 38), phaeochromocytoma (n = 27), metastasis to the adrenal gland (n = 11) and benign tumours (n = 40) (cortical adenoma, 23; cyst, two; cortical hyperplasia, five; ganglioneuroma, four; myelolipoma, six). The median size of the adrenal cortical carcinomas was 9·2 (range 1·7–30) cm; five tumours were smaller than 5·0 cm. The median overall size of the benign tumours (excluding phaeochromocytomas) was 4·0 cm; the median size of the adrenal cortical adenomas was 3·0 cm. Eleven benign tumours were larger than 5·0 cm, including two cortical adenomas. The radiographic features of three of five small adrenal cancers correctly predicted malignancy; the remaining two patients with small cancers had symptoms related to functioning tumours. Conversely, the radiographic features of seven of 11 large benign adrenal tumours correctly predicted benign histology, including five of five myelolipomas.

Conclusion

While size remains a good predictor of histology and clinical behaviour of functioning and non-functioning adrenal neoplasms, both small adrenal cortical cancers and large benign tumours occur with measurable frequency. High-quality imaging studies (computed tomography and magnetic resonance imaging) may be helpful in identifying relatively small yet radiographically atypical adrenal tumours more likely to be cancers, as well as radiographically characteristic benign myelolipomas which may be followed selectively.

Structure of the mouse calcitonin/calcitonin gene-related peptide alpha and beta genes

We report the cloning, genomic organization and sequence of the mouse alpha-CALC and beta-CALC genes. The two genes share extensive sequence homology. The transcription units of both genes contain 6 exons. Transcripts of the alpha-CALC gene were found to alternatively include exon 4 or exons 5 and 6. For the beta-CALC gene exon 4 was not detected in transcripts derived from this gene. The predicted mouse alpha-CGRP was found to be identical to rat alpha-CGRP, however, beta-CGRP predicted amino acid sequences revealed three amino acid differences suggesting these residues are not critical to CGRP function.

Nonfunctioning islet cell carcinoma of the pancreas: survival results in a contemporary series of 163 patients

BACKGROUND

The natural history of nonfunctioning islet cell carcinoma of the pancreas is poorly defined. We therefore reviewed our institutional experience during a period of 12 years to define more clearly the natural history of this disease as a basis for individual therapeutic recommendations.

METHODS

The records of all patients who had histologically or cytologically confirmed nonfunctioning islet cell carcinoma of the pancreas were retrospectively reviewed. Patients were grouped by extent of disease at diagnosis and by initial treatment. Survival distributions were estimated by Kaplan-Meier analysis.

RESULTS

One hundred sixty-three patients with nonfunctioning islet cell carcinoma of the pancreas were identified. The overall median survival duration was 3.2 years. The median survival was 7.1 years in patients with localized disease who underwent a potentially curative resection and 5.2 years in those with locally advanced, unresectable, nonmetastatic disease (P = .04). Patients with metastatic disease that could not be resected had a median survival of 2.1 years.

CONCLUSIONS

Patients with completely resected localized disease had a long median survival. Patients with nonmetastatic but unresectable locally advanced disease also had a surprisingly long median survival; major treatment-related morbidity may be hard to justify in this subgroup. The short median survival in patients with metastatic disease suggests that the frequent practice of observation in this patient subgroup needs to be reexamined and that continued investigation of regional and systemic therapies with novel agents is warranted.

Guidelines for diagnosis and therapy of MEN type 1 and type 2

This is a consensus statement from an international group, mostly of clinical endocrinologists. MEN1 and MEN2 are hereditary cancer syndromes. The commonest tumors secrete PTH or gastrin in MEN1, and calcitonin or catecholamines in MEN2. Management strategies improved after the discoveries of their genes. MEN1 has no clear syndromic variants. Tumor monitoring in MEN1 carriers includes biochemical tests yearly and imaging tests less often. Neck surgery includes subtotal or total parathyroidectomy, parathyroid cryopreservation, and thymectomy. Proton pump inhibitors or somatostatin analogs are the main management for oversecretion of entero-pancreatic hormones, except insulin. The roles for surgery of most entero-pancreatic tumors present several controversies: exclusion of most operations on gastrinomas and indications for surgery on other tumors. Each MEN1 family probably has an inactivating MEN1 germline mutation. Testing for a germline MEN1 mutation gives useful information, but rarely mandates an intervention. The most distinctive MEN2 variants are MEN2A, MEN2B, and familial medullary thyroid cancer (MTC). They vary in aggressiveness of MTC and spectrum of disturbed organs. Mortality in MEN2 is greater from MTC than from pheochromocytoma. Thyroidectomy, during childhood if possible, is the goal in all MEN2 carriers to prevent or cure MTC. Each MEN2 index case probably has an activating germline RET mutation. RET testing has replaced calcitonin testing to diagnose the MEN2 carrier state. The specific RET codon mutation correlates with the MEN2 syndromic variant, the age of onset of MTC, and the aggressiveness of MTC; consequently, that mutation should guide major management decisions, such as whether and when to perform thyroidectomy.

Evaluation and surgical resection of adrenal masses in patients with a history of extra-adrenal malignancy

BACKGROUND

Adrenal abnormalities are often identified on imaging studies performed during the staging of patients presenting with a new malignancy or restaging of patients with a history of a malignancy.

METHODS

We reviewed the records of patients who underwent surgical resection of an adrenal mass identified in the setting of previously or newly diagnosed extra-adrenal malignancy.

RESULTS

Eighty-one patients with an adrenal mass and recently diagnosed malignancy (n = 24) or history of a malignancy (n = 57) underwent adrenalectomy. In 42 patients (52%) the adrenal mass was a metastasis. In 39 patients (48%) the adrenal mass was an additional primary adrenal tumor process: 19 pheochromocytomas, (14 syndrome-associated, 5 sporadic), 13 cortical adenomas, 3 adrenocortical carcinomas, 2 ganglioneuromas, and 2 cases of nodular hyperplasia.

CONCLUSIONS

In this series nearly half of the patients with cancer and an adrenal mass had adrenal pathologic condition independent of their primary malignancy. Despite the presence of a newly diagnosed malignancy or history of malignancy, all patients with an adrenal mass should undergo a standard hormone evaluation to confirm that the mass is not a functional neoplasm. An assumption that the adrenal mass is metastatic disease will be wrong in up to 50% of such patients.

Allelic imbalance of the mutant and wild-type RET allele in MEN 2A-associated medullary thyroid carcinoma

Germline mutations of the RET proto-oncogene are responsible for the familial tumor syndrome called multiple endocrine neoplasia type 2 (MEN 2) that includes medullary thyroid carcinoma (MTC). Although inherited mutations of RET lead to tumor formation in patients with MEN 2, it is not understood why only selected cells develop into tumors. We have recently shown that duplication of the mutated RET allele or loss of the wild-type allele might represent mechanisms of tumorigenesis in patients with MEN 2A-related pheochromocytoma. We now analysed 19 DNA samples of MTC (15 of which were non-microdissected, four of which were microdissected) from patients with MEN 2A. Using polymorphic marker and phosphorimage densitometry analyses, we found allelic imbalance of the mutated and wild-type RET allele in six of 19 DNA MTC samples. Of note, two of the four microdissected tumor DNA samples showed allelic imbalance of RET, whereas only four of the 15 non-microdissected MTC samples did. These results underscore the significance of microdissection in the analysis of tumor DNA. In our study, some of the non-microdissected tumor DNA samples may have failed to display allelic imbalance of RET, because of contamination of tumor DNA with nonneoplastic DNA or noninformative microsatellite marker analysis. Taken together, our results suggest allelic imbalance between mutated and wild-type RET as a possible mechanism for tumor formation in some patients with MEN 2A-related MTC.

Promiscuity of pre-mRNA spliceosome-mediated trans splicing: a problem for gene therapy?

Trans splicing of messenger RNA has been used in experimental settings to replace mutant RNA sequences. We investigated the feasibility of utilizing trans splicing to replace a mutant RET protooncogene sequence known to inappropriately activate this tyrosine kinase receptor. We constructed a pre-trans-splicing molecule (PTM) consisting of a binding domain complementary to the target intron, the 3' splicing signal sequence (3'ss), derived from adenovirus major late transcript intron 1 and a molecular tag sequence. Accurately targeted trans splicing between the human RET exons and the PTM was demonstrated in NIH 3T3 cells cotransfected with the human RET minigene and the PTM. The efficiency of specific trans splicing was estimated to be no more than 15% in the cotransfection experiment. However, in addition to the targeted trans splicing, nontargeted trans splicing to RET exons was observed. Furthermore, the rapid amplification of 5' cDNA ends (5' RACE) analysis demonstrated that nontargeted trans splicing occurred with endogenously expressed pre-mRNAs in TT cells and that specific trans splicing to RET was a rare event. Attempts to reduce nonspecificity by the addition of a stem-loop to the trans-splicing construct designed to suppress nonspecific splicing failed to have the desired effect. These observations suggest that overexpression of a trans-splicing construct containing a 3'ss results in promiscuous trans splicing and raise significant questions about the specificity and usefulness of currently used trans-splicing approaches. In addition, these findings raise the possibility that nonspecific spliced products may be produced by a variety of gene therapy constructs.

[Germline mutations of the ret proto-oncogene in Chilean patients with hereditary and sporadic medullary thyroid carcinoma]

BACKGROUND

Medullary thyroid carcinoma (MTC) may occur either as a sporadic or familial disease. Multiple endocrine neoplasia (MEN) type 2, inherited as an autosomal dominant disease, is characterized by MTC only (FMTC) or coexistence of MTC with other endocrine neoplasia (NEM 2A, 2B). Germline mutations of the RET proto-oncogene (cRet) are found in the inherited forms and in some apparently sporadic MTC cases.

AIM

To study RET mutations in 8 families with MEN 2.

MATERIAL AND METHODS

RET mutations were screened in peripheral blood DNA from 18 patients and 87 high risk carriers belonging to 8 MEN 2 families and 52 sporadic MTC. Exons 10, 11, 13, 14, 15 and 16 of the c-Ret were amplified by polymerase chain reaction (PCR) and examined by direct sequencing of PCR products and/or restriction enzyme analysis.

RESULTS

Five MEN 2A and one FMTC families with a germline mutation at codon 634, one MEN 2A and one FMTC family carrying a mutation at codon 620 were identified. Mutations were found in 23 out of 87 high risk carriers. In addition, we detected a S891A (exon 15) germline mutation in a sporadic MTC patient and in one out of her three sons and V804M (exon 14) in another sporadic MTC case and in one out of his six relatives, indicating in both cases the presence of a sporadic misclassified familial disease.

CONCLUSIONS

These results underscore the importance of routine application of c-Ret testing in all cases of MTC either familial or sporadic.

Adrenal cortical carcinoma

Adrenal cortical carcinoma is a rare endocrine tumor for which complete surgical resection is the only potentially curative treatment. Accurate preoperative evaluation (biochemical and radiographic) of the patient who presents with an adrenal mass maximizes the opportunity for the patient to undergo a complete, margin-negative resection of the primary tumor, which is the most powerful prognostic variable for long-term survival. The response to chemotherapy or mitotane is modest in patients with advanced disease. Hopefully, an improved understanding of the molecular pathogenesis of this challenging tumor will lead to the development of more effective therapies in the future.

Alternative ribonucleic acid processing in endocrine systems

Alternative RNA processing is a mechanism for creation of protein diversity through selective inclusion or exclusion of RNA sequence during posttranscriptional processing. More than one-third of human pre-mRNAs undergo alternative RNA processing modification, making this a ubiquitous biological process. The protein isoforms produced have distinct and sometimes opposite functions, underscoring the importance of this process. This review focuses on important endocrine genes regulated by alternative RNA processing. We discuss how diverse events such as spermatogenesis or GH action are regulated by this process. We focus on several endocrine (calcitonin/calcitonin gene-related peptide) and nonendocrine (Drosophila doublesex and P-element and mouse c-src) examples to highlight recent progress in the elucidation of molecular mechanisms regulating this process. Finally, we outline methods (model systems and techniques) used by investigators in this field to study processing of individual pre-mRNAS:

Arthritic calcitonin/alpha calcitonin gene-related peptide knockout mice have reduced nociceptive hypersensitivity

Peripheral inflammation induced with a knee joint injection of a mixture of kaolin/carrageenan (k/c) produces primary and secondary hyperalgesia. Inflammatory pain is thought to involve a variety of transmitters released from nerve terminals, including amino acids, substance P (SP) and calcitonin gene-related peptide (CGRP). In the present study, mice deficient in the calcitonin/alpha CGRP gene (CGRP(-/-)) displayed normal responses to noxious stimuli. However, the CGRP knockout mice failed to demonstrate development of secondary hyperalgesia after induction of knee joint inflammation in two tests that assess central sensitization, through testing at sites remote from the primary insult. Nociceptive behavioral responses were assessed using the hot-plate test and paw withdrawal latency (PWL) to radiant heat applied to the hindpaw. The CGRP(-/-) mice showed no signs of secondary hyperalgesia after development of knee joint inflammation, while the expected significant decrease in the PWL was observed in the CGRP(+/+) mice as control. The CGRP(-/-) mice also had a prolonged rather than a shortened response latency in the hot-plate test 4 h after knee joint injection of k/c. Immunohistological study showed that CGRP-like immunoreactivity (CGRP-LI) was absent in the spinal cord and dorsal root ganglia taken from the CGRP(-/-) mice. These results indicate that endogenous CGRP plays an important role in the plastic neurogenic changes occurring in response to peripheral inflammatory events including the development of nociceptive behaviors.

Limitations of size as a criterion in the evaluation of adrenal tumors

BACKGROUND

Size has been considered to be the single best predictor of malignancy in adrenal neoplasms that have been identified incidentally. However, small adrenal cortical cancers have been reported from multiple centers.

METHODS

We retrospectively evaluated the value of tumor size and other clinical parameters in the prediction of the presence of adrenal malignancy.

RESULTS

The records of 117 patients who underwent evaluation for tumors of the adrenal gland were reviewed. The median tumor size of the adrenal cortical carcinomas (n = 38 carcinomas) was 9.2 cm (range, 1.7-30 cm); 5 cancers (13.5%) were smaller than 5.0 cm. The median overall size of the benign tumors, excluding pheochromocytomas, was 4.0 cm (n = 38 carcinomas); 10 benign tumors (26%) were larger than 5.0 cm. The imaging features of 4 of 5 small adrenal cancers predicted malignancy; the remaining patients had hormonally functioning tumors. The imaging features of 7 of 10 large benign adrenal tumors predicted benign histologic features, including 5 of 5 myelolipomas.

CONCLUSIONS

Although size remains a good predictor of the histologic features and clinical behavior of adrenal neoplasms, both small adrenal cortical cancers and large benign tumors occur with measurable frequency. High-quality imaging studies may be helpful in the identification of relatively small adrenal cancers and of characteristic benign lesions that may be selectively followed.

Quinagolide in the management of prolactinoma

OBJECTIVE

This study reports a six year experience with quinagolide (CV205-502) in the treatment of 40 patients with hyperprolactinemia or prolactinoma.

PATIENTS AND MEASUREMENTS

Forty patients with hyperprolactinemia were treated with quinagolide (CV 205-502, Norprolac) for 2-72 months (mean 31.6 months). The patient's ages ranged from 12 to 53 years and 90% were female. Seventeen had no radiologic evidence of tumor; 11 had microadenomas; and 12 had macroadenomas.

RESULTS

All patients had a reduction of the serum prolactin following quinagolide therapy with normalization in 82% with no tumor, 73% with microadenomas, and 67% with macroadenomas. Fifty-five percent of microadenoma and 75% of macroadenoma patients had a decrease in tumor size when assessed by a blinded reviewer. Ten of 38 female patients became pregnant while taking quinagolide. The dosage of quinagolide ranged from 75 to 400 [mgr]g/day with a median dose of 100[mgr]g/day. A comparison of side effects in a subgroup of 35 patients who had taken bromocriptine prior to quinagolide administration showed a greater than 75% reduction in nausea, vomiting, dizziness, and drowsiness during quinagolide administration.

CONCLUSIONS

We conclude that quinagolide is a safe and effective long-term alternative to bromocriptine therapy, particularly in those individuals with bromocriptine intolerance.

Duplication of the mutant RET allele in trisomy 10 or loss of the wild-type allele in multiple endocrine neoplasia type 2-associated pheochromocytomas

Inherited mutations of the RET proto-oncogene are tumorigenic in patients with multiple endocrine neoplasia type 2 (MEN 2). However, it is not understood why only few of the affected cells in the target organs develop into tumors. Genetic analysis of nine pheochromocytomas from five unrelated patients with MEN 2 showed either duplication of the mutant RET allele in trisomy 10 or loss of the wild-type RET allele. Our results suggest a "second hit" causing a dominant effect of the mutant RET allele, through either duplication of the mutant allele or loss of the wild-type allele, as a possible mechanism for pheochromocytoma tumorigenesis in patients with MEN 2.

Hypercalcemia due to parathyroid hormone-related protein secretion by melanoma

About 1-2% of melanoma patients develop hypercalcemia. We report hypercalcemia without bone metastasis in a 46-year-old woman with advanced melanoma. The hypercalcemia was associated with elevated serum parathyroid hormone-related protein (PTHrP) levels. An even higher concentration (10 times the serum level) in pleural effusion caused by pleural metastases implied that the source of the increased circulating PTHrP was the melanoma. Immunohistochemical staining of paraffin sections, performed using a monoclonal antibody (9H7) against the peptide sequence 109-141 of human PTHrP, detected PTHrP in the cytoplasm and nucleoli of melanoma cells in an autopsy specimen but not in specimens from this patient prior to onset of hypercalcemia. Considering the evidence, it is very likely that PTHrP production by melanoma caused hypercalcemia in this patient.

Multiple endocrine neoplasias

The multiple endocrine neoplasia syndromes form a distinct group of genetic tumor syndromes. They include multiple endocrine neoplasia types 1 and 2, von Hippel Lindau syndrome, neurofibromatosis, and Carney complex. Research over the past decade has identified a molecular basis for each of these syndromes. This knowledge has revolutionized not only the clinical management but also has illuminated the field of human cancer research by the identification of new and important genes critical for regulation of cell growth, differentiation, and death. This review focuses on the structure, physiologic function, and molecular abnormalities of the genes involved in these syndromes.

Relative contributions of technetium Tc 99m sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay to the surgical management of hyperparathyroidism

HYPOTHESIS

Technetium Tc 99m sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay have been used to permit a directed operation in patients with hyperparathyroidism. We hypothesized that the coordinated use of these techniques might be particularly useful in patients who require a second operation for hyperparathyroidism.

DESIGN

Retrospective analysis was performed to determine the specific contribution of these technologies to the surgical management of patients with hyperparathyroidism who underwent evaluation by at least 2 of these techniques between April 1996 and October 1999.

SETTING

Patients were evaluated and treated by an endocrine tumor surgery group within a tertiary care referral center.

PATIENTS

Coordinated application of 99mTc-sestamibi scintigraphy, intraoperative gamma probe detection, and/or the rapid parathyroid hormone assay was performed in 32 patients.

RESULTS

Twenty-eight of 32 patients had primary hyperparathyroidism, 3 had multiple endocrine neoplasia type 1, and 1 had secondary hyperparathyroidism. The surgical procedure was an initial cervical exploration in 19 and a second operative procedure in 13. Parathyroidectomy was successful in all patients. A directed anatomic operation was performed in 24 patients, including 11 patients who underwent second operative procedures and 9 patients who underwent minimally invasive procedures under local anesthesia. A directed operation was facilitated by sestamibi scan in 22 of 24 patients, intraoperative gamma probe detection in 5 of 23 patients, and the rapid parathyroid hormone assay in 15 of 15 patients.

CONCLUSIONS

Coordinated application of 99mTc-sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay allows for successful directed reoperative parathyroidectomy; a minimally invasive procedure may be performed in selected patients.

Pituitary carcinoma containing gonadotropins: treatment by radical excision and cytotoxic chemotherapy: case report

OBJECTIVE AND IMPORTANCE

Pituitary carcinomas are extremely rare. Cases reported in the medical literature in the 20th century included tumors that produced adrenocorticotropic hormone, prolactin, growth hormone, and/or thyrotropin.

CLINICAL PRESENTATION

Here we present a 22-year-old woman with a pituitary carcinoma that was immunohistochemically positive for luteinizing hormone and follicle-stimulating hormone at both the primary and metastatic sites. The patient exhibited elevated serum levels of alpha-subunit.

INTERVENTION

The patient had experienced failure of previous treatments, including standard surgery and radiotherapy, and presented to us for radical resection of the tumor, with exenteration of the involved cavernous sinus. She was pretreated with cytotoxic chemotherapy and continued to receive this therapy after surgery.

CONCLUSION

This is the only documented case of a gonadotropin-staining pituitary carcinoma for which hormone production was proven in both the primary and metastatic tumors. Many benign "nonsecreting" pituitary adenomas actually produce subclinical amounts of gonadotropins, and malignant nonfunctional pituitary neoplasms may do the same.

Use of long-term intravenous phosphate infusion in the palliative treatment of tumor-induced osteomalacia

Tumor-induced osteomalacia is characterized by paraneoplastic defects in vitamin D metabolism, proximal renal tubular functions, and phosphate transport. The resulting hypophosphatemia can cause generalized pain and muscle weakness, which significantly affect the quality of life of the patients. Palliative treatment with calcium, vitamin D, and phosphate replacement is indicated for patients in whom the causative tumor cannot be completely resected. In this report we describe a case of tumor-induced osteomalacia in whom adequate oral doses of phosphate could not be used because of gastrointestinal side-effects. Long term (3-6 months) iv phosphate infusion delivered by ambulatory infusion pumps in combination with oral calcium and vitamin D was used successfully to decrease pain and increase muscle strength. Careful monitoring of serum calcium, phosphate, and creatinine levels and reliable microinfusion technology have allowed the long term use of iv phosphate infusion without serious morbidity. This patient received repeated (three times) phosphate infusions over 8 yr, resulting in laboratory and symptomatic improvement after each course. However, this patient did suffer two episodes of central venous catheter-related infection. Because of potentially serious complications, such as severe hypocalcemia, calcified right ventricular thrombi, and nephrocalcinosis, long term iv phosphate infusion should be reserved for patients who cannot tolerate adequate doses of oral phosphate and for whom the benefits outweigh the risks.

Increased blood pressure in alpha-calcitonin gene-related peptide/calcitonin gene knockout mice

Nerves that contain calcitonin gene-related peptide (CGRP) are components of the sensory nervous system. Although these afferent nerves have traditionally been thought to sense stimuli in the periphery and transmit the information centrally, they also have an efferent vasodilator function. Acute administration of a CGRP receptor antagonist increases the blood pressure (BP) in several models of hypertension, which indicates that this potent vasodilator plays a counterregulatory role to attenuate the BP increase in these settings. To determine the role of this peptide in the long-term regulation of cardiovascular function, including hypertension, we obtained mice that have a deletion of the alpha-calcitonin gene-related peptide (alpha-CGRP) gene. Although the beta-calcitonin gene-related peptide (beta-CGRP) gene is intact in these mice, alpha-CGRP is by far the predominant species of CGRP produced in dorsal root ganglia (DRG) sensory neurons. Initially, we examined the effect of deletion of the alpha-CGRP on baseline BP and beta-CGRP and substance P mRNA expression. Systolic BP was significantly higher in the knockout mice (n=7) compared with wild-type in both male (160+/-6.1 vs 125+/-4.8 mm Hg) and female (163+/-4.8 vs 135+/-33 mm Hg) mice. Next, groups (n=7) of knockout and wild-type mice had catheters surgically placed in the right carotid artery for mean arterial pressure recording. With the animals fully awake and unrestrained, the knockout mice displayed an elevated mean arterial pressure compared with wild-type in both male (139+/-4.9 vs 118+/-4.9 mm Hg) and female (121+/-3.4 vs 107+/-3.1 mm Hg) mice. Northern blot analysis of DRG RNA samples confirmed the absence of alpha-CGRP mRNA in the knockout mice. Substance P mRNA content in DRG was unchanged between the 2 groups; however, beta-CGRP mRNA levels were reduced 2-fold in the knockout mice. These results indicate for the first time that alpha-CGRP may be involved in the long-term regulation of resting BP and suggest that these mice are particularly sensitive to challenges to BP homeostasis because of the loss of a compensatory vasodilator mechanism.

Calcium-induced activation of a mutant G-protein-coupled receptor causes in vitro transformation of NIH/3T3 cells

The calcium-sensing receptor (CaR) is a G-protein-coupled receptor that is widely expressed, has tissue-specific functions, and regulates cell growth. Activating mutations of this receptor cause autosomal dominant hypocalcemia, a syndrome characterized by hypocalcemia and hypercalciuria. The identification of a family with an activating mutation of the CaR (Thr151Met) in which hypocalcemia cosegregates with several unusual neoplasms led us to examine the transforming effects of this mutant receptor. Transfection of NIH/3T3 cells with the mutant but not the normal receptor supported colony formation in soft agar at subphysiologic calcium concentrations. The mutant CaR causes a calcium-dependent activation of the extracellular signal-regulated protein kinase (ERK) 1/2 and Jun-N-terminal kinase/stress-activated (JNK/ SAPK) pathways, but not P38 MAP kinase. These findings contribute to a growing body of information suggesting that this receptor plays a role in the regulation of cellular proliferation, and that aberrant activation of the mutant receptor in this family may play a role in the unusual neoplastic manifestations.

Screening for MEN1 mutations in patients with atypical endocrine neoplasia

BACKGROUND

Most patients from typical multiple endocrine neoplasia type 1 (MEN1) kindreds harbor mutations in the MEN-1 gene, MEN1. We hypothesized that some patients with atypical endocrine neoplasia would also have mutations in MEN1.

METHODS

DNA sequencing analysis of mutations in the coding region of MEN1 was performed with genomic DNA obtained from peripheral blood lymphocytes in a total of 21 patients who had: typical MEN1 (n = 8), clinical features suggestive of MEN1 but without a family history of endocrinopathy (n = 7), and atypical endocrine neoplasia and a family history of endocrinopathy suggestive of MEN1 (n = 6).

RESULTS

All 8 patients with typical MEN1 had mutations in MEN1. None of the 7 patients with features of MEN1, but without a family history of endocrinopathy, had a MEN1 mutation. In contrast, 4 of 6 patients with atypical endocrine neoplasia that included components of MEN1 and a family history of endocrinopathy had mutations in MEN1, including 2 patients with pheochromocytoma.

CONCLUSIONS

Genomic mutations in MEN1 may frequently be identified in patients with atypical endocrine neoplasia, especially in the setting of a family history of endocrinopathy. Atypical presentations of MEN1 may include pheochromocytoma.

Surgical strategy for the treatment of medullary thyroid carcinoma

OBJECTIVE

To evaluate surgical complications, patterns of lymph node metastases, and calcitonin response to compartment-oriented lymphadenectomy in patients with primary or recurrent medullary thyroid carcinoma (MTC).

SUMMARY BACKGROUND DATA

The majority of patients with invasive MTC have metastasis to regional lymph nodes at the time of diagnosis, as evidenced by the frequent finding of persistently elevated calcitonin levels after thyroidectomy and the high rates of recurrence in the cervical lymph nodes reported in retrospective studies. These data have provided the rationale for surgeons to perform a more extensive lymphadenectomy at the time of initial thyroidectomy and to consider reoperative cervical lymphadenectomy in patients with persistently elevated calcitonin levels after thyroidectomy.

METHODS

Forty patients underwent surgery for MTC from 1991 to 1997 (23 sporadic cases, 17 familial cases). Patients were divided into three groups based on whether they had undergone previous thyroidectomy and on the results of standardized staging studies performed after referral to the authors' institution. Group 1 (11 patients) had received no previous surgery; group 2 (13) underwent thyroidectomy before referral and had an elevated calcitonin level without radiologic evidence of local regional or distant metastases; and group 3 (16) underwent thyroidectomy before referral and had an elevated calcitonin level with radiologic evidence of local-regional recurrence. The central neck compartment was dissected in all patients; preoperative staging and the extent of previous surgery dictated the need for lateral (modified radical) neck dissection. After primary or reoperative surgery, calcitonin levels were assessed.

RESULTS

All patients had major reductions in postoperative calcitonin levels. Seven (29%) of 24 patients in groups 1 and 2 achieved normal calcitonin values compared with only 1 (6%) of 16 in group 3. Postoperative complications included seven cases (17%) of permanent hypoparathyroidism; five (71%) of these occurred in group 3. There were no iatrogenic recurrent laryngeal nerve injuries; one patient required recurrent nerve resection to achieve complete tumor extirpation. At a median follow up of 35 months, local recurrence was documented in 5 (13%) of 40 patients.

CONCLUSIONS

Compartment-oriented lymphadenectomy performed early in the course of MTC is safe and may return calcitonin levels to normal in up to 25% of carefully selected patients. However, reoperation for bulky cervical disease (group 3) rarely results in normal calcitonin levels and is associated with a high incidence of permanent hypoparathyroidism.

Hammerhead ribozyme-mediated inactivation of mutant RET in medullary thyroid carcinoma

Activating mutations of the RET proto-oncogene cause hereditary medullary thyroid carcinoma. To examine whether selective inactivation of mutant RET could prevent transformation, a hammerhead ribozyme was designed to cleave RET mRNA containing a transforming mutation of codon 634 TGC --> TAC (Cys634Tyr). In vitro RNA cleavage assay demonstrated that the ribozyme selectively cleaved RET RNA with a Cys634Tyr but not Cys634Arg or the normal sequence. Expression of ribozyme in NIH/3T3 cells prevented RET-mediated colony formation in soft agar. This inhibition required catalytically active ribozyme and was specific for the TAC mutation. Therefore, ribozymes designed to selectively target mutant RET RNA may provide an effective therapeutic in the treatment of this syndrome.

A codon 891 exon 15 RET proto-oncogene mutation in familial medullary thyroid carcinoma: a detection strategy

A ser891ala RET proto-oncogene mutation has been previously discovered in a single kindred with familial medullary thyroid carcinoma (FMTC). An additional two probands with this mutation and with medullary thyroid carcinoma (MTC) without any other manifestations of MEN 2 have been identified. In one of thse families, two other individuals also had the mutant sequence and FMTC. Analysis of both cases showed cosegregation of the mutation and MTC. To facilitate detection of this mutation, a primer was engineered which creates a Hha I recognition site in the presence of the mutant sequence. As a result, this codon 891 exon 15 mutation can be identified with a restriction enzyme digestion.

The surgical treatment of medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is a unique disease in solid tumor oncology due to its ability to secrete calcitonin (iCT), a highly sensitive and specific serum marker of persistent or recurrent disease even at a microscopic level. The relatively long duration of survival experienced by most patients with MTC combined with the visible nature of surgical complications, when they occur, has caused most surgeons to take a conservative approach to the operative management and follow-up of patients with MTC. In contrast, the patient, family physician, and endocrinologist watch the iCT slowly rise, indicative of persistent and usually progressive invasive cancer. Amidst this clinical dilemma, we developed a standardized diagnostic and operative strategy to maximize local-regional tumor control and facilitate patient management.

Polypyrimidine tract-binding protein positively regulates inclusion of an alternative 3'-terminal exon

Polypyrimidine tract-binding protein (PTB) is an abundant vertebrate hnRNP protein. PTB binding sites have been found within introns both upstream and downstream of alternative exons in a number of genes that are negatively controlled by the binding of PTB. We have previously reported that PTB binds to a pyrimidine tract within an RNA processing enhancer located adjacent to an alternative 3'-terminal exon within the gene coding for calcitonin and calcitonin gene-related peptide. The enhancer consists of a pyrimidine tract and CAG directly abutting on a 5' splice site sequence to form a pseudoexon. Here we show that the binding of PTB to the enhancer pyrimidine tract is functional in that exon inclusion increases when in vivo levels of PTB increase. This is the first example of positive regulation of exon inclusion by PTB. The binding of PTB was antagonistic to the binding of U2AF to the enhancer-located pyrimidine tract. Altering the enhancer pyrimidine tract to a consensus sequence for the binding of U2AF eliminated enhancement of exon inclusion in vivo and exon polyadenylation in vitro. An additional PTB binding site was identified close to the AAUAAA hexanucleotide sequence of the exon 4 poly(A) site. These observations suggest a dual role for PTB in facilitating recognition of exon 4: binding to the enhancer pyrimidine tract to interrupt productive recognition of the enhancer pseudoexon by splicing factors and interacting with the poly(A) site to positively affect polyadenylation.

Unknown primary cancer presenting as an adrenal mass: frequency and implications for diagnostic evaluation of adrenal incidentalomas

BACKGROUND

Fine-needle aspiration biopsy to identify adrenal metastasis from an occult primary malignancy has been recommended as part of the evaluation of the patient who presents with an incidentally discovered adrenal mass. This recommendation was assessed by examining the frequency of adrenal involvement in patients with suspected unknown primary cancer.

METHODS

Data from 1715 patients referred for evaluation of suspected unknown primary cancer were retrospectively reviewed.

RESULTS

Of 1639 patients found to have cancer, the adrenal gland was identified as a site of involvement at presentation in 95 (5.8%). Involvement was limited to the adrenal gland in 4 patients (0.2%). All 4 patients had large (> or = 6 cm) adrenal tumors, 3 of 4 had bilateral involvement, and all had symptoms that otherwise mandated evaluation for an occult malignancy; none had a true adrenal incidentaloma.

CONCLUSIONS

Although cancer of an unknown primary site occasionally involves the adrenal gland, metastatic cancer presenting as a true adrenal incidentaloma is extremely rare. Therefore, in the absence of a history of prior malignancy or symptoms, physical examination findings, radiographic findings, or laboratory findings suggestive of an occult malignancy, we do not recommend fine-needle aspiration biopsy as part of the diagnostic evaluation of the patient who presents with a unilateral adrenal mass.

Regulation of alternative polyadenylation by U1 snRNPs and SRp20

Although considerable information is currently available about the factors involved in constitutive vertebrate polyadenylation, the factors and mechanisms involved in facilitating communication between polyadenylation and splicing are largely unknown. Even less is known about the regulation of polyadenylation in genes in which 3'-terminal exons are alternatively recognized. Here we demonstrate that an SR protein, SRp20, affects recognition of an alternative 3'-terminal exon via an effect on the efficiency of binding of a polyadenylation factor to an alternative polyadenylation site. The gene under study codes for the peptides calcitonin and calcitonin gene-related peptide. Its pre-mRNA is alternatively processed by the tissue-specific inclusion or exclusion of an embedded 3'-terminal exon, exon 4, via factors binding to an intronic enhancer element that contains both 3' and 5' splice site consensus sequence elements. In cell types that preferentially exclude exon 4, addition of wild-type SRp20 enhances exon 4 inclusion via recognition of the intronic enhancer. In contrast, in cell types that preferentially include exon 4, addition of a mutant form of SRp20 containing the RNA-binding domain but missing the SR domain inhibits exon 4 inclusion. Inhibition is likely at the level of polyadenylation, because the mutant SRp20 inhibits binding of CstF to the exon 4 poly(A) site. This is the first demonstration that an SR protein can influence alternative polyadenylation and suggests that this family of proteins may play a role in recognition of 3'-terminal exons and perhaps in the communication between polyadenylation and splicing.

Mutational analysis of the GDNF/RET-GDNFR alpha signaling complex in a kindred with vesicoureteral reflux

Glial cell line-derived neurotrophic factor (GDNF) mediates signaling across the cell membrane by interaction with the RET-GDNFR alpha receptor complex. We identified a family in which one member had medullary thyroid carcinoma (MTC) and four members had vesicoureteral reflux (VUR). Knowledge that mutations in the RET proto-oncogene cause MTC and studies documenting genitourinary abnormalities in RET or GDNF knockout mice led us to examine the GDNF/RET-GDNFR alpha signaling complex in this family. RET and GDNF were excluded as the causative VUR gene by haplotype and sequence analysis. The GDNFR alpha gene was mapped to chromosome 10q25-26 by radiation hybrid techniques and was eliminated as the causative gene by haplotype analysis and sequencing of cDNA from an obligate carrier. Sequencing identified a 15-nucleotide deletion in GDNFR alpha mRNA, which was found to code for a single exon; analysis of several cell types revealed an identical mRNA form, indicating that this variant is a product of alternative RNA processing. We conclude that GDNFR alpha maps to 10q25-26 and that its RNA transcript is alternatively processed. Mutation abnormalities in the GDNF/RET-GDNFR alpha signaling system do not cause VUR in this family.

Alternative RNA processing--its role in regulating expression of calcitonin/calcitonin gene-related peptide

The calcitonin/calcitonin gene-related peptide (CT/CGRP) gene is one of the earliest studied examples of alternative RNA processing. The regulatory mechanisms controlling this event are poorly understood. We have identified and characterized an intron element residing in intron 4 of the human CT/CGRP gene. This intron element functions to enhance polyadenylation of an embedded alternative 3'-terminal exon within the CT/CGRP gene and is potentially involved in tissue-specific regulation of CT/CGRP RNA processing.

Bone turnover response to changes in calcium intake is altered in girls and adult women in families with histories of osteoporosis

Heredity and environmental factors contribute to the development of osteoporosis. Because calcium is the major mineral in bone and adolescence is a key period in bone acquisition, we hypothesized that bone turnover would be less responsive to alterations in dietary calcium intake in both girls and adult women from families with histories of osteoporosis. To address this issue, we studied calcium kinetics in the maternal grandmother (age range 56-81 years), mother (age range 32-47 years), and granddaughter (age range 8-15 years) in 10 multigenerational families. In five families, the mother and/or grandmother had osteoporosis (bone mineral density > or = 2 SD below the age-specific mean). To examine both active and passive calcium absorption, families consumed low- (279 +/- 64 mg/day) and high- (1580 +/- 385) calcium diets for 10 days prior to administration of oral (46Ca) and intravenous (42Ca) stable isotopes. Using repeated measures analysis of variance, fractional calcium absorption, true calcium absorption, bone calcium deposition, and the balance in bone calcium turnover were all significantly affected by diet (p < 0.01). Females from nonosteoporotic families had decreased bone calcium resorption with little change in bone calcium deposition during the high-calcium study. In contrast, girls and adult women from osteoporotic families had increased both bone calcium deposition and resorption during the high-calcium period, leading to a less positive balance in bone calcium turnover. A significant interaction between bone status and diet was found for bone calcium resorption (p < 0.05) and approached significance for bone calcium deposition (p < 0.07), effects which were independent of generation. We conclude that girls and women from osteoporotic families have a significantly altered bone turnover response to acute changes in calcium intake.

An overview of molecular abnormalities leading to thyroid carcinogenesis: a 1993 perspective

This discussion reviews molecular abnormalities in thyroid carcinoma and points out areas where these molecular defects might be applicable to thyroid carcinogenesis induced by radiation exposure. Both medullary and papillary follicular thyroid carcinoma are discussed. The multiple endocrine neoplasia type 2 gene on chromosome 10 is one of the genes responsible for medullary thyroid carcinoma. Genes thought to be involved in papillary and follicular thyroid carcinoma include the gsp, ret, trk, ras, met, and p53 oncogenes. Research is continuing to: A) find new genes whose regulation and/or expression may be responsible for these disorders; B) determine the mechanisms by which gene mutations can lead to thyroid carcinogenesis, and C) devise methods to prevent or counter the effects of these mutational events.

Unresolved issues in the genesis and management of multiple endocrine neoplasia type 2

It has been slightly less than 3 years since mutations of the RET proto-oncogene were identified in multiple endocrine neoplasia type 2. The period since the initial report has been one of intense activity with a wide spectrum of mutations identified in exons 10, 11, 13, 14, 15 and 16 of this gene. Recent studies have provided experimental evidence for an activating effect of the exon 11 and 16 mutations. Two questions are addressed in this report: the high rate of false positive tests in prospective screening studies and the implications for future interpretation of this test: and the mechanism of transformation in MEN 2.

Multiple endocrine neoplasia type II and familial medullary thyroid carcinoma. Impact of genetic screening on management

The identification of ret protooncogene mutations in MEN-II and Hirschsprung disease has not only improved the clinical management of these genetic conditions but has also provided important information regarding mechanisms of transformation and neural crest development. An indication of how neural-crest cells migrate during embryonic life and the key processes involved in their differentiation now seems within reach. The continued pace of scientific discovery suggests that our understanding of and ability to prevent or treat hereditary and sporadic forms of MTC will continue to improve.