Plasma immunoreactive calcitonin in lung cancer

Prophylactic thyroidectomy in multiple endocrine neoplasia type 2A

BACKGROUND

Medullary thyroid carcinoma is the most common cause of death in patients with multiple endocrine neoplasia (MEN) type 2A (MEN-2A) or type 2B or familial medullary thyroid carcinoma. We sought to determine whether total thyroidectomy in asymptomatic young members of kindreds with MEN-2A who had a mutated allele of the RET proto-oncogene could prevent or cure medullary thyroid carcinoma.

METHODS

A total of 50 patients 19 years of age or younger who were consecutively identified through a genetic screening program as carriers of a RET mutation characteristic of MEN-2A underwent total thyroidectomy. Five to 10 years after the surgery, each patient was evaluated by physical examination and by determination of plasma calcitonin levels after stimulation with provocative agents.

RESULTS

In 44 of the 50 patients, basal and stimulated plasma calcitonin levels were at or below the limits of detection of the assay (proportion, 0.88; 95 percent confidence interval, 0.76 to 0.95). Two patients had basal and stimulated plasma calcitonin levels above the normal range. Stimulated plasma calcitonin levels had increased but remained within the normal range in four patients. The data suggest that there was a lower incidence of persistent or recurrent disease in children who underwent total thyroidectomy before eight years of age and in children in whom there were no metastases to cervical lymph nodes.

CONCLUSIONS

In this study, young patients identified by direct DNA analysis as carriers of a RET mutation characteristic of MEN-2A had no evidence of persistent or recurrent medullary thyroid carcinoma five or more years after total thyroidectomy. A longer period of evaluation will be necessary to confirm that they are cured.

Adrenocorticotropin, calcitonin, and antidiuretic hormone as tumor markers in patients with bronchogenic carcinoma of various histological types

We measured basal and dexamethasone-suppressed plasma ACTH in 246 patients with bronchogenic carcinoma (105 with small-cell carcinoma); in 138 of these patients (67 with small-cell carcinoma) basal and pentagastrin-stimulated serum calcitonin was also determined. In addition, in a subgroup of 120 patients (58 with small-cell carcinoma) plasma ADH with reference to plasma osmolality was also assayed. Non-suppressible plasma ACTH was found in 45% of patients with small-cell carcinoma but only in isolated cases of large-cell carcinoma, adenocarcinoma, and squamous-cell carcinoma. Serum calcitonin was increased in 28% of patients with small-cell carcinoma but only in few patients with other tumor types. Stimulation of calcitonin by pentagastrin was ineffective. Plasma ADH was inappropriately high in 47% of patients with small-cell carcinoma. Strikingly high also was the incidence of increased ADH concentrations in patients with large-cell (40%), adenocarcinoma (46%), and squamous-cell carcinoma (29%). By measuring plasma ACTH after dexamethasone suppression and ADH with reference to osmolality, the sensitivity of these tumor markers in detecting pathological hormone secretion is markedly increased. In small-cell carcinoma the simultaneous measurement of ACTH, ADH, and calcitonin gives a high yield of positive results (74%), indicating that this set of tumor markers is a promising aid in diagnosis and therapy control.

Human lung small-cell carcinoma contains bombesin

The presence of immunoreactive bombesin in a human lung small-cell carcinoma grown in nude mice was established by several criteria: (i) Radioimmunoassay of tissue extracts for bombesin revealed approximately 6.5 pmol/g of tissue; (ii) bombesin was found in 12-14% of the tumor cells by immunohistochemical localization; (iii) gel filtration of small-cell carcinoma extract on Sephadex G-75 and Bio-Gel P-4 gave only a single peak of immunoreactivity, which occurred at the elution volume of bombesin; and (iv) reverse-phase HPLC of acid-solubilized extracts separated the immunoreactive material into three discrete peaks, one of which eluted with a retention time identical to that of synthetic bombesin. The presence of bombesin may represent the ectopic expression of this peptide in small-cell carcinoma, because immunoreactive bombesin was found in human fetal and neonatal lung but apparently not in adult lung tissue [Wharton, J., Polak, J. M., Bloom, S. R., Ghatei, M. A., Solcia, E., Brown, M. R. & Pearse, A. G. E. (1978) Nature (London) 273, 769-770]. The immunoreactive bombesin previously found in mammalian tissues is considerably larger than amphibian bombesin; these data substantiate the presence of a mammalian form of bombesin in a human tumor that may have a structure similar to that of the amphibian peptide.

Paired-ion reversed-phase high-performance liquid chromatography of human and rat calcitonin

Improved methods for isolation, characterization, and quantitation of immunochemically heterogeneous forms of calcitonin (CT) in tissue and plasma must be developed before the biological origins and clinical importance of CT moieties can be elucidated. We are now proposing reversed-phase high-performance liquid chromatography (RP-HPLC) as one possible means of achieving high recovery, high resolution of CT moieties. In this paper we report RP-HPLC analyses of trace amounts of radiolabeled and unlabeled synthetic human and rat CT. We have systematically evaluated our application of RP-HPLC by employing several elution modes, including isocratic and gradient elution, as well as several elution reagents. We determined that high recovery and high resolution were best achieved with alkyl ion-pairing reagents, such as tetrabutylammonium phosphate, pH 7.5, or sodium sulfonyl hexane, pH 3.5. The most sensitive UV detection of trace amounts of CT was achieved with tetrabutylammonium phosphate buffer (TBAP). We recommend for RP-HPLC of CT a C18-bonded silica column and elution with a 20-min linear gradient of methanol-water (20:80 to 80:20, v/v) containing 0.005 M TBAP. Combined with appropriate extraction procedures, such as silica adsorption or immuno-adsorbant chromatography, this paired-ion RP-HPLC method can be an important aid in achieving more accurate and extensive information about CT moieties in biological samples. This method will also allow the rapid, optical detection and quantitation of CT moieties recovered from tissues, and perhaps from plasmas.