The Na(+)/I(-) symporter (NIS) is an integral plasma membrane glycoprotein that mediates active I(-) transport into the thyroid follicular cells, the first step in thyroid hormone biosynthesis. NIS-mediated thyroidal I(-) transport from the bloodstream to the colloid is a vectorial process made possible by the selective targeting of NIS to the basolateral membrane. NIS also mediates active I(-) transport in other tissues, including salivary glands, gastric mucosa, and lactating mammary gland, in which it translocates I(-) into the milk for thyroid hormone biosynthesis by the nursing newborn. NIS provides the basis for the effective diagnostic and therapeutic management of thyroid cancer and its metastases with radioiodide. NIS research has proceeded at an astounding pace after the 1996 isolation of the rat NIS cDNA, comprising the elucidation of NIS secondary structure and topology, biogenesis and posttranslational modifications, transcriptional and posttranscriptional regulation, electrophysiological analysis, isolation of the human NIS cDNA, and determination of the human NIS genomic organization. Clinically related topics include the analysis of congenital I(-) transport defect-causing NIS mutations and the role of NIS in thyroid cancer. NIS has been transduced into various kinds of cancer cells to render them susceptible to destruction with radioiodide. Most dramatically, the discovery of endogenous NIS expression in more than 80% of human breast cancer samples has raised the possibility that radioiodide may be a valuable novel tool in breast cancer diagnosis and treatment.

The sodium/iodide Symporter (NIS): characterization, regulation, and medical significance.

The late health effects associated with radioiodine ((131)I) given as treatment for thyroid cancer are difficult to assess since the number of thyroid cancer patients treated at each centre is limited. The risk of second primary malignancies (SPMs) was evaluated in a European cohort of thyroid cancer patients. A common database was obtained by pooling the 2-year survivors of the three major Swedish, Italian, and French cohorts of papillary and follicular thyroid cancer patients. A time-dependent analysis using external comparison was performed. The study concerned 6841 thyroid cancer patients, diagnosed during the period 1934-1995, at a mean age of 44 years. In all, 17% were treated with external radiotherapy and 62% received (131)I. In total, 576 patients were diagnosed with a SPM. Compared to the general population of each of the three countries, an overall significantly increased risk of SPM of 27% (95% CI: 15-40) was seen in the European cohort. An increased risk of both solid tumours and leukaemias was found with increasing cumulative activity of (131)I administered, with an excess absolute risk of 14.4 solid cancers and of 0.8 leukaemias per GBq of (131)I and 10(5) person-years of follow-up. A relationship was found between (131)I administration and occurrence of bone and soft tissue, colorectal, and salivary gland cancers. These results strongly highlight the necessity to delineate the indications of (131)I treatment in thyroid cancer patients in order to restrict its use to patients in whom clinical benefits are expected.

Second primary malignancies in thyroid cancer patients

Thyroid iodide uptake is basic to the clinical applications of radioiodine. Iodide uptake occurs across the membrane of the thyroid follicular cells through an active transporter process mediated by the sodium iodide symporter (NIS). The recent cloning of the NIS gene enabled the better characterization of the molecular mechanisms underlying iodide transport, thus opening the way to the clarification and expansion of its role in nuclear medicine. In papillary and follicular carcinoma, NIS immunostaining was positive in only a few tumor cells, and no NIS protein expression was detected in anaplastic carcinomas. Decreased NIS expression levels account for the reduced iodide uptake in thyroid carcinomas. Thus, by targeting NIS expression in cancer cells, we could enable these cells to concentrate iodide from plasma and in so doing offer the possibility of radioiodine therapy. Several investigators have shown that gene transfer of NIS into a variety of cell types confers increased radioiodine uptake by up to several hundredfold that of controls in nonthyroid cancers as well as in thyroid cancer. In addition, my group proposes that NIS may serve as an alternative imaging reporter gene in addition to the HSVtk and dopaminergic receptor genes. The NIS has the potential to expand the role of nuclear medicine in the future, just as it has served as the base for the development of nuclear medicine in the past.

http://jnm.snmjournals.org/content/43/9/1188.full.pdf

Sodium iodide symporter: its role in nuclear medicine.

The recent completion of the human genome sequence has raised great hopes for the discovery of new breast cancer therapies based on newly-discovered genes linked to breast cancer development and progression. Here we describe breast cancer therapies that have emerged from gene-based scientific efforts over the past 20 years and that are now approved for clinical testing or treatment.

Molecular targets for breast cancer therapy and prevention.

Extrathyroidal cancers could potentially be targeted with 131 I, if the Na/I symporter (NIS) were functional. Using immunohistochemical methods we probed 1278 human samples with anti-NIS antibody, including 253 thyroid and 169 breast conventional whole tissue sections (CWTS). Four high density tissue microarrays containing a wide variety of breast lesions, normal tissues, and carcinoma cores were tested. The results of the normal microarray were corroborated in 50 CWTS. Nineteen of 34 normal tissues, including bladder, colon, endometrium, kidney, prostate, and pancreas, expressed NIS. Nineteen of 25 carcinomas demonstrated NIS immunopositivity; 55.7% of 479 carcinoma microarray cores expressed NIS, including prostate (74%), ovary (73%), lung (65%), colon (62.6%), and endometrium (56%). NIS protein was present in 75% benign thyroid lesions, 73% thyroid cancers, 30% normalappearing, peritumoral breasts, 88% ductal carcinomas in situ, and 76% invasive breast carcinoma CWTS. Comparatively, breast microarray cores had lower immunoreactivity. Plasma membrane immunopositivity was confirmed in thyrocytes, salivary ductal, gastric mucosa, and lactating mammary cells. In other tissues, immunoreactivity was predominantly intracellular, particularly in malignant lesions. Thus, NIS is present in many normal epithelial tissues and is predominantly expressed intracellularly in many carcinomas. Elucidating the regulatory mechanisms that render NIS functional in extrathyroidal carcinomas may make 131 I therapy feasible. (J Clin Endocrinol Metab 88: 1880 –1888, 2003)

Immunohistochemical profile of the sodium/iodide symporter in thyroid, breast, and other carcinomas using high density tissue microarrays and conventional sections.

The sodium/iodide symporter mediates active iodide transport in both healthy and cancerous thyroid tissue. By exploiting this activity, radioiodide has been used for decades with considerable success in the detection and treatment of thyroid cancer. Here we show that a specialized form of the sodium/iodide symporter in the mammary gland mediates active iodide transport in healthy lactating (but not in nonlactating) mammary gland and in mammary tumors. In addition to characterizing the hormonal regulation of the mammary gland sodium/iodide symporter, we demonstrate by scintigraphy that mammary adenocarcinomas in transgenic mice bearing Ras or Neu oncogenes actively accumulate iodide by this symporter in vivo. Moreover, more than 80% of the human breast cancer samples we analyzed by immunohistochemistry expressed the symporter, compared with none of the normal (nonlactating) samples from reductive mammoplasties. These results indicate that the mammary gland sodium/iodide symporter may be an essential breast cancer marker and that radioiodide should be studied as a possible option in the diagnosis and treatment of breast cancer.

The mammary gland iodide transporter is expressed during lactation and in breast cancer

Monoclonal antibodies and antibody-derived biologics are essential tools for cancer research and therapy. The development of monoclonal antibody treatments for successful tumor-targeted therapies took several decades. A nanobody constructed by molecular engineering of heavy-chain-only antibody, which is unique in camel or alpaca, is a burgeoning tools of diagnostic and therapeutic in clinic. In this study, we immunized a 4-year-old female alpaca with TIM-3 antigen. Then, a VHH phage was synthesized from the transcriptome of its B cells by nested PCR as an intermediate library; the library selection for Tim-3 antigen is carried out in three rounds of translation. The most reactive colonies were selected by periplasmic extract monoclonal ELISA. The nanobody was immobilized by metal affinity chromatography (IMAC) purification with the use of a Ni-NTA column, SDS-PAGE, and Western blotting. Finally, the affinity of TIM3-specific nanobody was determined by ELISA. As results, specific 15 kD bands representing nanomaterials were observed on the gel and confirmed by Western blotting. The nanobody showed obvious specific immune response to Tim-3 and had high binding affinity. We have successfully prepared a functional anti-human Tim-3 nanobody with high affinity in vitro.

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Development and Characterization of a Nanobody against Human T-Cell Immunoglobulin and Mucin-3

Purpose Antibody-drug conjugates (ADCs) have emerged as a potent cancer therapeutic option in recent years. DP303c is a HER2-targeting ADC with a cleavable linker-MMAE payload. The current study aimed to evaluate the therapeutic potentials of DP303c in vitro as well as in vivo. Materials and Methods Size exclusion chromatography (SEC), reverse-phase high-performance liquid chromatography (RP-HPLC), and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to analyze the physicochemical characterization of DP303c. An enzyme-linked immunosorbent assay (ELISA), a cell-based assay, and bio-layer interferometry (BLI) were used to evaluate DP303c’s affinity with HER2 and Fc receptors. A confocal laser scanning microscopy was used to observe the internalization of DP303c. Antibody-dependent cell-mediated cytotoxicity (ADCC) and cytotoxicity assays were used to investigate the activity of DP303c in vitro. The antitumor activity of DP303c was assessed in vivo in the HER2-positive cell-derived xenograft model. Results DP303c was a site-specific anti-HER2 antibody-drug conjugate with a monomethyl auristatin E (MMAE) with an average drug-to-antibody ratio (DAR) of 2.0. DP303c showed a high affinity with HER2 and could be effectively internalized. In vitro and in vivo, DP303c showed stronger antitumor activity as compared to trastuzumab-DM1 (T-DM1) in a series of HER2-positive cancer cells and cell-derived xenograft (CDX) models, especially in the lower HER2-expressing cells. DP303c also exhibited high serum stability and a good PK profile. Conclusion DP303c was a steady and homogenous DAR 2 ADC that was predicted to deliver MMAE inhibitor to tumor cells. DP303c demonstrated remarkable anticancer efficacy against T-DM1 in xenograft models. DP303c was a strong candidate for the treatment of patients with HER2-positive cancer.

https://www.dovepress.com/getfile.php?fileID=79766

Qing Hua Zhao

Papers

The mammary gland iodide transporter is expressed during lactation and in breast cancer

Development and Characterization of a Nanobody against Human T-Cell Immunoglobulin and Mucin-3

An Innovative Site-Specific Anti-HER2 Antibody-Drug Conjugate with High Homogeneity and Improved Therapeutic Index