Papillary carcinoma of the thyroid: evidence for a role for hepatocyte growth factor (HGF) in promoting tumour angiogenesis

Identification of high-risk factors for recurrence of colon cancer following complete mesocolic excision: An 8-year retrospective study

BACKGROUND

Colon cancer recurrence is a common adverse outcome for patients after complete mesocolic excision (CME) and greatly affects the near-term and long-term prognosis of patients. This study aimed to develop a machine learning model that can identify high-risk factors before, during, and after surgery, and predict the occurrence of postoperative colon cancer recurrence.

METHODS

The study included 1187 patients with colon cancer, including 110 patients who had recurrent colon cancer. The researchers collected 44 characteristic variables, including patient demographic characteristics, basic medical history, preoperative examination information, type of surgery, and intraoperative information. Four machine learning algorithms, namely extreme gradient boosting (XGBoost), random forest (RF), support vector machine (SVM), and k-nearest neighbor algorithm (KNN), were used to construct the model. The researchers evaluated the model using the k-fold cross-validation method, ROC curve, calibration curve, decision curve analysis (DCA), and external validation.

RESULTS

Among the four prediction models, the XGBoost algorithm performed the best. The ROC curve results showed that the AUC value of XGBoost was 0.962 in the training set and 0.952 in the validation set, indicating high prediction accuracy. The XGBoost model was stable during internal validation using the k-fold cross-validation method. The calibration curve demonstrated high predictive ability of the XGBoost model. The DCA curve showed that patients who received interventional treatment had a higher benefit rate under the XGBoost model. The external validation set's AUC value was 0.91, indicating good extrapolation of the XGBoost prediction model.

CONCLUSION

The XGBoost machine learning algorithm-based prediction model for colon cancer recurrence has high prediction accuracy and clinical utility.

Gene Signatures Induced by Ionizing Radiation as Prognostic Tools in an In Vitro Experimental Breast Cancer Model

Simple Summary

The present work analyzed the expression of genes involved in radiation, using an in vitro experimental breast cancer model developed by the combined treatment of low doses of high linear energy transfer (LET) radiation α particle radiation and estrogen yielding different stages in a malignantly transformed breast cancer cell model called Alpha model. Results showed important findings of genes involved in cancers of the breast, lung, and nervous system, and others. Most of those genes analyzed in these studies such as ATM, selenoproteins, GABA receptor, interleukins, epsin, and cathepsin inhibitors like stefins, and metallothioneins can be used for new prognostic tools and future therapies since they affect cancer progression and metastasis. In conclusion, gene signature demonstrated to be specific to cell line types, hence cell-dependency must be considered in future radiotherapy treatment planning since molecular and clinical features affect such results. Thus, using gene technology and molecular information is possible to improve therapies and reduction of side effects.

Abstract

This study aimed to analyze the expression of genes involved in radiation, using an Affymetrix system with an in vitro experimental breast cancer model developed by the combined treatment of low doses of high linear energy transfer (LET) radiation α particle radiation and estrogen yielding different stages in a malignantly transformed breast cancer cell model called Alpha model. Altered expression of different molecules was detected in the non-tumorigenic Alpha3, a malignant cell line transformed only by radiation and originally derived from the parental MCF-10F human cell line; that was compared with the Alpha 5 cell line, another cell line exposed to radiation and subsequently grown in the presence 17β-estradiol. This Alpha5, a tumorigenic cell line, originated the Tumor2 cell line. It can be summarized that the Alpha 3 cell line was characterized by greater gene expression of ATM and IL7R than control, Alpha5, and Tumor2 cell lines, it presented higher selenoprotein gene expression than control and Tumor2; epsin 3 gene expression was higher than control; stefin A gene expression was higher than Alpha5; and metallothionein was higher than control and Tumor2 cell line. Therefore, radiation, independently of estrogen, induced increased ATM, IL7R, selenoprotein, GABA receptor, epsin, stefin, and metallothioneins gene expression in comparison with the control. Results showed important findings of genes involved in cancers of the breast, lung, nervous system, and others. Most genes analyzed in these studies can be used for new prognostic tools and future therapies since they affect cancer progression and metastasis. Most of all, it was revealed that in the Alpha model, a breast cancer model developed by the authors, the cell line transformed only by radiation, independently of estrogen, was characterized by greater gene expression than other cell lines. Understanding the effect of radiotherapy in different cells will help us improve the clinical outcome of radiotherapies. Thus, gene signature has been demonstrated to be specific to tumor types, hence cell-dependency must be considered in future treatment planning. Molecular and clinical features affect the results of radiotherapy. Thus, using gene technology and molecular information is possible to improve therapies and reduction of side effects while providing new insights into breast cancer-related fields.

Anti-angiogenic Therapy for Retinal Disease

Recent breakthroughs in our understanding of the molecular pathophysiology of retinal vascular disease have allowed us to specifically target pathological angiogenesis while minimizing damage to the neurosensory retina. This is perhaps best exemplified by the development of therapies targeting the potent angiogenic growth factor and vascular permeability mediator, vascular endothelial growth factor (VEGF). Anti-VEGF therapies, initially introduced for the treatment of choroidal neovascularization in patients with age-related macular degeneration, have also had a dramatic impact on the management of retinal vascular disease and are currently an indispensable component for the treatment of macular edema in patients with diabetic eye disease and retinal vein occlusions. Emerging evidence supports expanding the use of therapies targeting VEGF for the treatment of retinal neovascularization in patients with diabetic retinopathy and retinopathy of prematurity. However, VEGF is among a growing list of angiogenic and vascular hyperpermeability factors that promote retinal vascular disease. Many of these mediators are expressed in response to stabilization of a single family of transcription factors, the hypoxia-inducible factors (HIFs), that regulate the expression of these angiogenic stimulators. Here we review the basic principles driving pathological angiogenesis and discuss the current state of retinal anti-angiogenic pharmacotherapy as well as future directions.

The roles and role-players in thyroid cancer angiogenesis

Thyroid cancer is the most prevalent endocrine cancer worldwide. Angiogenesis, the formation of new blood vessels, plays a pivotal role in the development and progression of tumors. Over the past years, cancer research has focused on the ability of tumors to induce newly formed blood vessel, because tumor growth and the process of cancer metastasis mainly depends on angiogenesis. Tumor neovascularization occurs following the imbalance between pro-angiogenic and anti-angiogenic factors until the tumor switches to an angiogenic phenotype. A number of signaling factors and receptors that are implicated in the regulation of angiogenesis have been identified and characterized; most notably, the vascular endothelial growth factors (VEGFs) family and their receptors, which are the main pro-angiogenic molecules during early development and in pathological conditions such as cancer. Although thyroid is a highly vascularized organ, angiogenic switch in tumors of this organ leads to the formation of a vast network of blood vessels that favors the dissemination of tumor cells to distant organs and results in deterioration of patient conditions. Accordingly, the identification of key angiogenic biomarkers for thyroid cancer can facilitate diagnosis, prognosis and clinical decision-making and also may help to discover targeting factors for effective cancer therapy as well as monitoring response to therapy. Hence, the main purposes of this review are to summarize the types and mechanisms of angiogenesis emphasizing the prominent factors implicated in thyroid cancer angiogenesis.

Liver regeneration microenvironment in liver cancer: Research progress and prospect

The proposal of the new concept of liver regeneration microenvironment in liver cancer (LC) contributes to the overall understanding of how LC microenvironment influences the occurrence and development of LC through liver regeneration microenvironment, inflammatory microenvironment, immune microenvironment, and angiogenesis microenvironment, and helps explore more comprehensive and effective preventive and therapeutic measures for LC to improve the capability of LC prevention and cure. On the basis of eliminating hepatocellular carcinoma cells or tissues, the maintenance of normal liver regeneration and improvement of liver regeneration microenvironment in LC is an important strategy for LC prevention and treatment. Improving liver regeneration microenvironment to prevent or reverse the occurrence, development, and metastasis of LC should be an important research direction of LC prevention and treatment research. In recent years, traditional Chinese medicine research and application have made some progress in improving liver regeneration microenvironment to prevent or reverse the occurrence, development, recurrence, and metastasis of LC. However, it remains to be solved on how to accurately reveal the comprehensive network mechanism and how to provide advanced evidence-based medical evidence, which needs further extensive research.

Microenvironment of liver regeneration in liver cancer

The occurrence and development of liver cancer are essentially the most serious outcomes of uncontrolled liver regeneration. The progression of liver cancer is inevitably related to the abnormal microenvironment of liver regeneration. The deterioration observed in the microenvironment of liver regeneration is a necessary condition for the occurrence, development and metastasis of cancer. Therefore, the use of a technique to prevent and treat liver cancer via changes in the microenvironment of liver regeneration is a novel strategy. This strategy would be an effective way to delay, prevent or even reverse cancer occurrence, development and metastasis through an improvement in the liver regeneration microenvironment along with the integrated regulation of multiple components, targets, levels, channels and time sequences. In addition, the treatment of "tonifying Shen (Kidney) to regulate liver regeneration and repair by affecting stem cells and their microenvironment" can regulate "the dynamic imbalance between the normal liver regeneration and the abnormal liver regeneration"; this would improve the microenvironment of liver regeneration, which is also a mechanism by which liver cancer may be prevented or treated.

Spotlight on lenvatinib in the treatment of thyroid cancer: patient selection and perspectives

Thyroid cancer is the most common endocrine malignancy, with over 60,000 cases reported per year in the US alone. The incidence of thyroid cancer has increased in the last several years. Patients with metastatic differentiated thyroid cancer (DTC) generally have a good prognosis. Metastatic DTC can often be treated in a targeted manner with radioactive iodine, but the ability to accumulate iodine is lost with decreasing differentiation. Until recently, chemotherapy was the only treatment in patients with advanced thyroid cancer, which is no longer amenable to therapy with radioactive iodine. The modest efficacy and significant toxicity of chemotherapy necessitated the need for urgent advances in the medical field. New insights in thyroid cancer biology propelled the development of targeted therapies for this disease, including the tyrosine kinase inhibitor sorafenib as salvage treatment for DTC. In 2015, the US Food and Drug Administration approved a second tyrosine kinase inhibitor, lenvatinib, for the treatment of radioiodine-refractory thyroid cancer. Although associated with a significant progression-free survival improvement as compared to placebo in a large Phase III study (median progression-free survival 18.2 vs 3.6 months; hazard ratio 0.21; 99% confidence interval 0.14-0.31; P<0.001), the benefit of lenvatinib needs to be proved in the context of associated moderate to severe toxicities that require frequent dose reduction and delays. This article reviews the evidence supporting the use of lenvatinib as salvage therapy for radioactive iodine-refractory thyroid cancer, with a focus on the toxicity profile of this new therapy.

NITRIC OXIDE SYNTHASE ACTIVITY AND ITS CONCENTRATION IN THE TISSUES OF HUMAN THYROID CARCINOMAS

The study of the activity of the constitutive form of nitric oxide synthase (cNOS) revealed that in the papillary thyroid carcinomas it corresponded to that detected in unchanged extratumoral tissue, while the enzyme activity in follicular carcinoma was half lesser. At the same time, the activity of inducible nitric oxide synthase (іNOS) was higher in the papillary and follicular carcinomas. Such changes in the enzyme activity were associated with an increase in its level in papillary carcinomas, and with minor changes in follicular carcinomas. In medullary carcinomas the parameters under study corresponded to those in unchanged tissue, and in the papillary carcinoma metastases without changes in enzyme activity of nitric oxide formation, the level of the latter was much higher. Elevated levels of nitric oxide and іNOS activity in papillary thyroid carcinomas did not depend significantly on the aggression characteristics of the latter, being however absent in tumors of T4 category on a background of reduced cNOS activity and less expressed in tumors surrounded by the tissue in the presence of a chronic thyroiditis. Furthermore, in the papillary carcinomas of papillary or follicular structure nitric oxide level did not differ from the normal range, being slightly higher in tumors of solid or heterogeneous structure with presence of solid areas, whereas in carcinomas of papillary-follicular structure it was twice, and in tissue of solidinsular structure three times higher. іNOS hyperactivity was observed in the carcinomas of different structure, except for tumors of solid structure, in the tumor of which enzyme activity was within the normal range, and in tumor of solid-insular structure where it was significantly higher (as well as cNOS activity) compared with tumors of other structure. Nitric oxide generating system is involved in the transformation of thyroid cells and progression of tumor growth, including through apoptosis regulation, as shown by the results of an analysis of data obtained both in the present study and previously. The nature of such involvement in papillary thyroid carcinomas with different histological structure is different. Key words: nitric oxide; constitutive and inducible nitric oxide synthase; thyroid carcinoma; apoptosis.

The Pathogenetic Role of the HGF/c-Met System in Papillary Carcinoma of the Thyroid

The MET oncogene encodes for Met protein, a trans-membrane tyrosine kinase identified as the high affinity receptor for hepatocyte growth factor (HGF). Immunohistochemical studies have demonstrated that Met protein is intensely expressed in tumor cells of >95% cases of thyroid papillary carcinoma. High density of Met protein in tumor cells is the result of increased transcription of a normal MET gene, probably due to a combination of intracellular and extracellular signals. Over-expression of Met protein is more pronounced at the invading front of the tumor and can profoundly affect the tumorigenesis of papillary carcinoma of the thyroid. In fact, Met protein-positive papillary carcinoma cells are highly responsive to hepatocyte growth factor (HGF), which is effective in stimulating tumor cell adhesion, migration and invasiveness. In addition, HGF stimulation of papillary carcinoma of the thyroid (PTC) cells causes up-regulation of COX-2 and down-regulation of CD82/KAI-1; both these molecules have a major role in controlling tumor cell invasiveness. Finally, HGF stimulation of tumor cells may significantly affect the tumor microenvironment. In fact, HGF induces tumor cells to release chemokines active in the recruitment of dendritic cells, and is involved in regulating the production of proangiogenic factors.

Hypoxia-inducible factor in thyroid carcinoma

Intratumoural hypoxia (low oxygen tension) is associated with aggressive disease and poor prognosis. Hypoxia-inducible factor-1 is a transcription factor activated by hypoxia that regulates the expression of genes that promote tumour cell survival, progression, metastasis, and resistance to chemo/radiotherapy. In addition to hypoxia, HIF-1 can be activated by growth factor-signalling pathways such as the mitogen-activated protein kinases- (MAPK-) and phosphatidylinositol-3-OH kinases- (PI3K-) signalling cascades. Mutations in these pathways are common in thyroid carcinoma and lead to enhanced HIF-1 expression and activity. Here, we summarise current data that highlights the potential role of both hypoxia and MAPK/PI3K-induced HIF-1 signalling in thyroid carcinoma progression, metastatic characteristics, and the potential role of HIF-1 in thyroid carcinoma response to radiotherapy. Direct or indirect targeting of HIF-1 using an MAPK or PI3K inhibitor in combination with radiotherapy may be a new potential therapeutic target to improve the therapeutic response of thyroid carcinoma to radiotherapy and reduce metastatic burden.

Angiogenesis in Malignant Thyroid Tumors

It is well known that radiation significantly impacts the morbidity of thyroid cancer and that is why Belarus has the highest incidence of the malignancy. Author describes statistical data, classification of angiogenesis, and typical pathological features of malignant thyroid diseases with regard to the vascular network.

The tyrosine kinase receptor c-met, its cognate ligand HGF and the tyrosine kinase receptor trasducers STAT3, PI3K and RHO in thyroid nodules associated with Hashimoto's thyroiditis: an immunohistochemical characterization

Hepatocyte growth factor (HGF) exerts proliferative activities in thyrocytes upon binding to its tyrosine kinase receptor c-met and is also expressed in benign thyroid nodules as well as in Hashimoto's thyroiditis (HT). The simultaneous expression of HGF/c-met and three trasducers of tyrosine kinase receptors (STAT3, PI3K, RHO) in both the nodular and extranodular tissues were studied by immunohistochemistry in 50 benign thyroid nodules (NGs), 25 of which associated with HT. The ligand/tyrosine kinase receptor pair HGF/c-met and the two trasducers PI3K and RHO were expressed in NGs, regardless of association with HT, with a higher positive cases percentage in HT-associated NGs compared to not HT-associated NGs (25/25 or 100% vs 7/25 or 28%; P<0.001). HGF, PI3K and RHO expression was only stromal (fibroblasts and endothelial cells), in all 32 reactive NGs, while c-met localization was consistently epithelial (thyrocyes). Immunoreactions for HGF, c-met, PI3K and RHO were also apparent in the extra-nodular tissue of HT specimens, where HGF and PI3K were expressed not only in stromal cells but also in thyrocyes along with the c-met. Finally, a positive correlation was observed between the proportion of HGF, c-met, PI3K follicular cells and the grade of lymphoid aggregates in HT. In conclusion, HGF, c-met, PI3K are much more frequently and highly expressed in HT compared to NGs, and among all NGs in those present in the context of HT. A paracrine effect of HFG/c-met on nodule development, based on the prevalent stromal expression, may be suggested along with a major role of HGF/c-met and PI3K in HT. Finally, the expression of such molecules in HT may be regulated by lymphoid infiltrate.

Serum hepatocyte growth factor is increased in Hashimoto's thyroiditis whether or not it is associated with nodular goiter as compared with healthy non-goitrous individuals

BACKGROUND

Some growth factors and cytokines are known to cooperate with TSH in thyroid nodular growth, but few data are available on their circulating levels in Hashimoto's thyroiditis (HT).

AIM

To evaluate in HT patients whether thyroid nodules are associated with variations in serum levels of hepatocyte growth factor (HGF) and interleukin-6 (IL-6).

SUBJECTS AND METHODS

Serum levels of HGF and IL-6 were measured by enzyme-linked immunosorbent assay in 176 euthyroid subjects, subdivided into 4 groups: A) HT patients with nodular goiter (no.=42); B) non-goitrous HT patients (no.=36); C) non-HT patients with nodular goiter (no.=48), and D) healthy subjects without thyroid disease (no.=50).

RESULTS

The highest concentrations of serumHGF were found in patients with nodular goiter, irrespective of the presence of associated HT (groups A and C). Nevertheless, in group A serum HGF levels were significantly higher than in group C (860.8+/-333.6 pg/ml vs 691.5+/-156 pg/ml, p<0.01). Moreover, though serum HGF levels in group B (578.3+/-217 pg/ml) were lower than in group A, they were significantly higher than in healthy controls (group D, 512.7+/-170.4 pg/ml, p<0.001). Serum IL-6 levels were similar in the two HT groups (A and B), and increased with respect to groups C and D.

CONCLUSIONS

Serum HGF is increased in HT, especially associated to thyroid nodules, as compared with healthy non-goitrous individuals.

RET/PTC1-driven neoplastic transformation and proinvasive phenotype of human thyrocytes involve Met induction and beta-catenin nuclear translocation

Activation of the RET gene by chromosomal rearrangements generating RET/PTC oncogenes is a frequent, early, and causative event in papillary thyroid carcinoma (PTC). We have previously shown that, in human primary thyrocytes, RET/PTC1 induces a transcriptional program including the MET proto-oncogene. In PTCs, beta-catenin is frequently mislocated to the cytoplasm nucleus. We investigated the interplay between Ret/ptc1 signaling and Met in regulating the proinvasive phenotype and beta-catenin localization in cellular models of human PTC. Here, we show that Met protein is expressed and is constitutively active in human thyrocytes exogenously expressing RET/PTC1 as well as a mutant (Y451F) devoid of the main Ret/ptc1 multidocking site. Both in transformed thyrocytes and in the human PTC cell line TPC-1, Ret/ptc1-Y451-dependent signaling and Met cooperated to promote a proinvasive phenotype. Accordingly, gene/functional silencing of either RET/PTC1 or MET abrogated early branching morphogenesis in TPC-1 cells. The same effect was obtained by blocking the common downstream effector Akt. Y451 of Ret/ptc1 was required to promote proliferation and nuclear translocation of beta-catenin, suggesting that these oncogene-driven effects are Met-independent. Pharmacologic inhibition of Ret/ptc1 and Met tyrosine kinases by the multitarget small molecule RPI-1 blocked cell proliferation and invasive ability and dislocated beta-catenin from the nucleus. Altogether, these results support that Ret/ptc1 cross talks with Met at transcriptional and signaling levels and promotes beta-catenin transcriptional activity to drive thyrocyte neoplastic transformation. Such molecular network, promoting disease initiation and acquisition of a proinvasive phenotype, highlights new options to design multitarget therapeutic strategies for PTCs.

A radiation-induced gene signature distinguishes post-Chernobyl from sporadic papillary thyroid cancers

We investigated selected gene targets to differentiate radiation-induced papillary thyroid cancers (PTCs) from other etiologies. Total RNA was isolated from 11 post-Chernobyl PTCs and 41 sporadic PTCs characterized by a more aggressive tumor type and lacking a radiation exposure history. RNA from 10 tumor samples from both groups was pooled and hybridized separately on a whole genome microarray for screening. Then 92 selected gene targets were examined quantitatively on each tumor sample using an RTQ-PCR-based low-density array (LDA). Screening for more than fivefold differences in gene expression between the groups by microarray detected 646 up-regulated and 677 down-regulated genes. Categorization of these genes revealed a significant (P < 0.0006) over-representation of the number of up-regulated genes coding for oxidoreductases, G-proteins and growth factors, while the number of genes coding for immunoglobulin appeared to be significantly down-regulated. With the LDA, seven genes (SFRP1, MMP1, ESM1, KRTAP2-1, COL13A1, BAALC and PAGE1) made a complete differentiation between the groups possible. Gene expression patterns known to be associated with a more aggressive tumor type in older patients appeared to be more pronounced in post-Chernobyl PTC, thus underlining the known aggressiveness of radiation-induced PTC. Seven genes were found that completely distinguished post-Chernobyl (PTC) from sporadic PTC.

Thyroid cancer and the immune system: a model for effective immune surveillance

Differentiated thyroid cancers, including papillary and follicular variants, are a useful model with which to examine interactions between cancer and the immune system. Differentiated thyroid cancers are detected in only 20,000 individuals annually in the USA, but thyroid microcarcinomas (< 1 cm in diameter) are far more common. This suggests that the immune system might restrain the growth of these microcarcinomas. On the clinical level, patients with lymphocytes that infiltrate into papillary thyroid cancer have improved survival, supporting the notion that immune system activation might improve this. Together, these observations suggest that the growth and distant spread of thyroid carcinoma are suppressed by mechanisms of immune surveillance, possibly involving lymphocytes, macrophages and their secreted products. In this review, we examine the general hypothesis of immune surveillance and the data pertaining to the roles of lymphocytes, dendritic cells and cytokines in the immune response against thyroid cancers.

Vascular endothelial growth factor in thyroid cancers

Vascular endothelial growth factor (VEGF) is an essential peptide in new vessel growth in physiology (endometrial growth, embryonic development); pathological conditions (diabetic retinopathy, rheumatoid arthritis); as well as in tumor cell growth, particularly distant metastases. This study focused on VEGF structure, receptors, and angiogensis in tumors, especially their roles in thyroid cancer. The VEGF mRNA undergoes alternative splicing events that generate four homodimeric isoforms, including VEGF121, VEGF165, VEGF189, or VEGF206. Using VEGF purified from a culture medium conditioned by A-431 human epidermoid carcinoma cells, VEGF-binding site complexes of 230, 170, and 125 kDa were detected on human umbilical vein endothelial cells. The VEGF specifically induced the tyrosine phosphorylation of a 190-kDa polypeptide, which had similar mass to the largest binding site detected through affinity cross-linking. A transmembrane receptor belongs to the tyrosine kinase family, fms-like tyrosine kinase (FLT). These receptor tyrosine kinases encoded by the FLT gene family have distinct functions in regulating blood vessel growth and differentiation. Regulation of VEGF is a complex, multistep mechanism in various kinds of cells and tissues. Hypoxia-dependent and -independent mechanisms are illustrated in different cancer tissues. Hypoxic tumor cells may switch to a proangiogenic phenotype, which increases VEGF transcription. Clinical applications of VEGF in cancer have included diagnosis, prediction of prognosis, and treatment in different solid tumors, including thyroid tumors. Studies involving thyroid cancer cell lines, serum level determination, immunohistocytochemical staining, molecular biological studies, and gene therapy to the in vivo clinical trials, have shown that antiangiogensis therapy can provide another treatment modality for thyroid cancer. Future studies focused on recombinant human anti-VEGF research involving patients with advanced thyroid cancer, and investigation of the protection of high-risk patients by using novel antiangiogenic vaccines, are warranted.

Pathogenetic mechanisms in thyroid follicular-cell neoplasia

Thyroid cancer is one of the few malignancies that are increasing in incidence. Recent advances have improved our understanding of its pathogenesis; these include the identification of genetic alterations that activate a common effector pathway involving the RET-Ras-BRAF signalling cascade, and other unique chromosomal rearrangements. Some of these have been associated with radiation exposure as a pathogenetic mechanism. Defects in transcriptional and post-transcriptional regulation of adhesion molecules and cell-cycle control elements seem to affect tumour progression. This information can provide powerful ancillary diagnostic tools and can also be used to identify new therapeutic targets.

Expression of c-kit, Flk-1, and Flk-2 receptors in benign and malignant tumors of follicular epithelial origin

BACKGROUND

Vascular endothelial growth factor (VEGF) is a key regulator of physiologic as well as pathologic angiogenesis. The response of VEGF to endothelial cell mitogenesis and survival, as well as angiogenesis and microvascular permeability, is mainly mediated through its receptor-2, VEGFR2 (kinase domain receptor or fetal liver kinase-1, KDR or Flk-1). This study aimed to detect the expression of VEGFR2 in various forms of thyroid tumors. In addition, the expression of Flk-2 (receptor for Flt-3) and c-Kit (receptor for steel locus factor), which shows strong similarity to Flk-1, was also examined in thyroid tumors.

METHODS

RT-PCR analyses of c-Kit and immunohistochemical staining of c-Kit, Flk-1, and Flk-2 were performed in archived samples of 18 papillary thyroid carcinoma (PTC), 9 follicular thyroid carcinoma (FTC), 12 follicular adenoma (FA), and 7 nodular goiter (NG) samples. The data were correlated to clinicopathologic features.

RESULTS

By RT-PCR analyses, c-Kit expression was detected in 22% (4/18) of PTC, 22% (2/9) of FTC, 25% (3/12) of FA, and 57% (4/7) of NG samples. However, positive immunostaining signals of c-Kit were only observed in 17% (3/18) of PTC samples, and not in the others. Similarly, Flk-1 expression was only detected by immunohistochemistry in 67% (12/18) of PTC and 43% (3/7) of NG samples, and not in the others. Interestingly, the expression of Flk-2 was found in 89% (16/18) of PTC, 89% (8/9) of FTC, 75% (9/12) of FA, and 29% (2/7) of NG samples. An inverse relationship of thyroid cancer size with Flk-2 expression was found.

CONCLUSION

Flk-2 expression was detected in various forms of thyroid tumors and increased Flk-2 expression was correlated with thyroid tumors with increased transforming activity, suggesting that Flk-2 is involved in pathogenic development of thyroid malignancy. Similarly, Flk-1 expression was also found in some thyroid tumors, while the expression of c-Kit-mediated pathways may not play a major role in thyroid tumorigenesis.

Hepatocyte growth factor (HGF) downregulates thrombospondin 1 (TSP-1) expression in thyroid papillary carcinoma cells

This study investigates the expression of thrombospondin-1 in papillary carcinoma of the thyroid and the role of Met-HGF interaction in TSP-1 regulation. In tissue sections, immunostaining for TSP-1 was associated with the fibrous tumour stroma, and showed areas of marked intensity adjacent to the basal membrane of tumour cells. Investigation of TSP-1 RNA expression showed that, in 10 of 14 cases, TSP-1 mRNA levels were significantly lower in tumour tissue (20-100% reduction; mean = 55% +/- 20; p = 0.001) than in the corresponding normal thyroid. Since it has been reported that HGF can downregulate the expression of TSP-1 mRNA, TSP-1 mRNA levels were measured in 7 primary cultures, established from thyroid papillary carcinomas (TPC), and in 1 TPC cell line prior to, or after, stimulation with HGF. A marked decrease in TSP-1 mRNA levels was observed after HGF stimulation in 6/7 primary cultures (60-100% decrease (mean = 79 +/- 15%; p = 0.006) and in the TPC cell line; moreover, the decrease in TSP-1 mRNA in cell extracts was associated with a decrease in TSP-1 protein in culture supernatants. The HGF activity was dose dependent and the downregulation lasted for at least 48 h after stimulation. The high-level expression of Met protein, the high-affinity receptor for HGF, in most cases of papillary carcinoma of the thyroid is consistent with the possibility that HGF-Met interaction plays a crucial role in regulating the expression of TSP-1 in this tumour type.

Discrimination of benign and malignant thyroid nodules by molecular profiling

BACKGROUND

The evaluation of thyroid nodules by fine-needle aspiration has been the standard for almost 30 years, despite significant shortcomings in sensitivity and specificity. Recent data from our laboratory have suggested that molecular profiling permits the discrimination of specific types of thyroid nodules. These studies were undertaken to determine whether molecular profiling can discriminate between benign and malignant thyroid nodules with the necessary sensitivity and specificity required of a screening test.

METHODS

Molecular profiles of 11 papillary thyroid carcinomas, 13 follicular variant of papillary thyroid carcinomas, 9 follicular thyroid carcinomas, and 26 benign tumors (follicular adenomas and hyperplastic nodules) were analyzed by oligonucleotide microarray analysis. A gene list was created based on 45 samples. Seventeen samples were then added to the analysis as unknowns. A hierarchical clustering analysis was performed on all 62 samples to examine the groups for potential differences and the ability of the gene list to distinguish tumor types.

RESULTS

Cluster analysis of all 62 samples produced 2 distinct groups, 1 containing the carcinomas and 1 containing the benign lesions. The sensitivity for a diagnosis of cancer was 91.7% with a specificity of 96.2% (3 follicular variant of papillary thyroid carcinomas clustered with the benign lesions). The cancer gene profiles contained both known cancer-associated genes (MET, galectin-3) and previously unidentified genes.

CONCLUSIONS

Molecular profiling readily distinguishes between benign and malignant thyroid tumors with excellent sensitivity and specificity. Elucidated genes may provide insight into the molecular pathogenesis of thyroid cancer. Gene profiling may significantly enhance the evaluation of thyroid nodules in the future.

Local factors regulating growth and function of human thyroid cells in vitro and in vivo

In vitro culture of thyroid follicles is often employed to study thyroid cell biology and the control of thyroid follicular cell growth. For acceptance as a valid model, cultures should maintain differentiated function, which can be measured as the organification of [Formula: see text] and/or the de novo synthesis of thyroid hormones. In this article, the properties and merits of the various in vitro cultures of thyroid follicular cells and the potential effects of thyroid-specific, secreted products (thyroid hormones, thyroglobulin) and autocrine factors (proteases, growth factors and inhibitors) on thyroid growth and function, are explored. The regulation of the secretion of autocrine/paracrine factors by thyroid follicular cells is reviewed and methods by which cells may defend themselves from the effects of bioactive growth factors are discussed with particular reference to FGF signalling. The role and regulation of plasminogen activator activity, which may be central to the release and/or activation of growth factors and their receptors, and the secretion of angiogenic factors are described.

The basement membrane matrix in malignancy

Cancer is the second most common cause of death among Americans, although for several age groups it ranks first. Most of these deaths are not due to the primary tumour but rather to tumour cell metastases to distant organs. There are many steps that lead to metastasis, all of which are being studied with the goal of preventing these fatalities. Normally, cells attach to the extracellular matrix to maintain tissue integrity. During cancer progression, cells become more motile and acquire invasive qualities. Tumour cells move along blood and lymph vessels or invade into them to travel to distant sites. Then, the tumour cells must attach to the vessel wall, extravasate from the vessel, invade the new tissue, proliferate, and form a secondary tumour. Angiogenesis, the formation of new blood vessels, is critical to survival of these cells at the new site and is also important for primary tumour growth and spread. Tumour cell metastasis is a complex cascade of sequential steps, each of which is not yet fully understood. Progress has been made in identifying several key activators, one of which is the extracellular matrix. A major tumour promoter is the glycoprotein laminin, which is predominantly found in the extracellular matrix produced by endothelial and epithelial cells. This review will follow the metastatic process with particular attention to the effect of laminin on tumour cells.