B-Raf(V600E) and thrombospondin-1 promote thyroid cancer progression

Although B-Raf(V600E) is the most common somatic mutation in papillary thyroid carcinoma (PTC), how it induces tumor aggressiveness is not fully understood. Using gene set enrichment analysis and in vitro and in vivo functional studies, we identified and validated a B-Raf(V600E) gene set signature associated with tumor progression in PTCs. An independent cohort of B-Raf(V600E)-positive PTCs showed significantly higher expression levels of many extracellular matrix genes compared with controls. We performed extensive in vitro and in vivo validations on thrombospondin-1 (TSP-1), because it has been previously shown to be important in the regulation of tumor angiogenesis and metastasis and is present in abundance in tumor stroma. Knockdown of B-Raf(V600E) resulted in TSP-1 down-regulation and a reduction of adhesion and migration/invasion of human thyroid cancer cells. Knockdown of TSP-1 resulted in a similar phenotype. B-Raf(V600E) cells in which either B-Raf(V600E) or TSP-1 were knocked down were implanted orthotopically into the thyroids of immunocompromised mice, resulting in significant reduction in tumor size and fewer pulmonary metastases from the primary carcinoma as compared with the control cells. Treatment of orthotopic thyroid tumors, initiated 1 week after tumor cell implantation with PLX4720, an orally available selective inhibitor of B-Raf(V600E), caused a significant tumor growth delay and decreased distant metastases, without evidence of toxicity. In conclusion, B-Raf(V600E) plays an important role in PTC progression through genes (i.e., TSP-1) important in tumor invasion and metastasis. Testing of a patient's thyroid cancer for B-Raf(V600E) will yield important information about potential tumor aggressiveness and also allow for future use of targeted therapies with selective B-Raf(V600E) inhibitors, such as PLX4720.

A novel orthotopic mouse model of human anaplastic thyroid carcinoma

BACKGROUND

Orthotopic mouse models of human cancer represent an important in vivo tool for drug testing and validation. Most of the human thyroid carcinoma cell lines used in orthotopic or subcutaneous models are likely of melanoma and colon cancer. Here, we report and characterize a novel orthotopic model of human thyroid carcinoma using a unique thyroid cancer cell line.

METHODS

We used the cell line 8505c, originated from a thyroid tumor histologically characterized by anaplastic carcinoma cell features. We injected 8505c cells engineered using a green fluorescent protein-positive lentiviral vector orthotopically into the thyroid of severe combined immunodeficient mice.

RESULTS

Orthotopic implantation with the 8505c cells produced thyroid tumors after 5 weeks, showing large neck masses, with histopathologic features of a high-grade neoplasm (anaplasia, necrosis, high mitotic and proliferative indexes, p53 positivity, extrathyroidal invasion, lymph node and distant metastases) and immunoprofile of follicular thyroid cell origin with positivity for thyroid transcription factor-1 and PAX8, and for cytokeratins.

CONCLUSIONS

Here we describe a novel orthotopic thyroid carcinoma model using 8505c cells. This model can prove to be a reliable and useful tool to investigate in vivo biological mechanisms determining thyroid cancer aggressiveness, and to test novel therapeutics for the treatment of refractory or advanced thyroid cancers.

Severe hypoglycaemia post-gastric bypass requiring partial pancreatectomy: evidence for inappropriate insulin secretion and pancreatic islet hyperplasia

AIMS/HYPOTHESIS

Postprandial hypoglycaemia following gastric bypass for obesity is considered a late manifestation of the dumping syndrome and can usually be managed with dietary modification. We investigated three patients with severe postprandial hypoglycaemia and hyperinsulinaemia unresponsive to diet, octreotide and diazoxide with the aim of elucidating the pathological mechanisms involved.

METHODS

Glucose, insulin, and C-peptide were measured in the fasting and postprandial state, and insulin secretion was assessed following selective intra-arterial calcium injection. Pancreas histopathology was assessed in all three patients.

RESULTS

All three patients had evidence of severe postprandial hyperinsulinaemia and hypoglycaemia. In one patient, reversal of gastric bypass was ineffective in reversing hypoglycaemia. All three patients ultimately required partial pancreatectomy for control of neuroglycopenia; pancreas pathology of all patients revealed diffuse islet hyperplasia and expansion of beta cell mass.

CONCLUSIONS/INTERPRETATION

These findings suggest that gastric bypass-induced weight loss may unmask an underlying beta cell defect or contribute to pathological islet hyperplasia, perhaps via glucagon-like peptide 1-mediated pathways.