Does sunitinib-induced hypothyroidism play a role in the activity of sunitinib in metastatic renal cell carcinoma?

BACKGROUND: The objective of this study was to evaluate if hypothyroidism developing during sunitib therapy in patients with metastatic renal cell carcinoma (mRCC) is associated with a better outcome. METHODS: Thirty-one consecutive patients with clear cell mRCC were retrospectively analyzed. Thyroid function was assessed prior to therapy, every 6 weeks during the first 6 months and every 2-4 months thereafter. Hypothyroidism was considered present if thyroid-stimulating hormone (TSH) exceeded the upper normal limit (UNL) with normal triiodothyronine (T3) and thyroxine (T4). RESULTS: Hypothyroidism occurred in 16 patients (52%) within 3 months (range 0.7-22.9) of treatment initiation. Thyroid replacement corrected TSH below the UNL in 10 patients (63%). The distribution according to Motzer prognostic criteria revealed good prognosis in 16 patients (52%), intermediate in 9 (29%) and poor in 6 (19%). The hypothyroid patients tended to have longer progression-free survival (PFS; median 12.2 vs. 9.4 months; p = 0.234) and longer survival (median 22.4 vs. 13.9 months; p = 0.234) than the euthyroid patients. Clinical benefits were similar in both groups. CONCLUSIONS: Hypothyroidism that develops in mRCC patients treated with sunitinib is associated with a trend toward prolonged PFS and survival, with a similar clinical benefit rate.

Radiosensitization and production of DNA double-strand breaks in U87MG brain tumor cells induced by tetraiodothyroacetic acid (tetrac).

We describe the steady-state levels and molecular and cellular repair of DNA double-strand breaks (DSBs) in tetraiodothyroacetic acid (tetrac)-treated human U87MG glioblastoma cells after x-irradiation in vitro. This study was conducted to provide a basis for our previous observation of radiosensitization and inhibition of cellular recovery after irradiation of tetrac-exposed GL261 murine brain tumor cells. We used the neutral comet assay to assess DSBs, and found that the steady-state DSB levels as indicated by the mean tail moment after a 1 h application of 2 nM tetrac at 37 °C was increased from a value of 6.1 in control cells to 12.4 in tetrac treated cells at 0 radiation dose. However, at all radiation doses, the induction curves of DSBs were parallel, suggesting that no interaction of tetrac with the initial physical-chemical actions of ionizing radiation occurred. Flow cytometric measurements indicated that this increase was not due to alterations in the relative percentages of U87MG cells throughout the cell cycle. In split-dose DNA repair studies we found that tetrac decreased the repair rate of U87 cells by a factor of 72.5%. This suggests that the radiosensitization from graded single doses of x-rays occurs as a consequence of tetrac inhibition of the post-irradiation repair process. These results link the previously noted changes in cellular endpoints to a molecular endpoint. That is, tetrac produces increased numbers of DSBs in the unirradiated steady-state coupled with a decreased repair rate of DSBs in fractionated radiation experiments.

Thyroid hormones and cancer: clinical studies of hypothyroidism in oncology.

PURPOSE OF REVIEW: To collect and assess clinical reports of a putative relationship between thyroid state and the biology of cancers of various types. RECENT FINDINGS: A number of prospective case-control studies reviewed here have suggested that subclinical hyperthyroidism increases risk of certain solid tumors and that spontaneous hypothyroidism may delay onset or reduce aggressiveness of cancers. Small case studies have reached similar conclusions. A controlled prospective trial of induced hypothyroidism beneficially affected the course of glioblastoma. A context in which to interpret such findings is the recent description of a plasma membrane receptor for thyroid hormone on cancer cells and dividing tumor-associated endothelial cells. SUMMARY: Accumulating clinical evidence may justify new, broadly-based controlled studies in cancer patients of the possible contribution of thyroid hormone to tumor behavior.

Modification of survival pathway gene expression in human breast cancer cells by tetraiodothyroacetic acid (tetrac).

Tetraiodothyroacetic acid (tetrac) inhibits the cellular actions of thyroid hormone initiated at the hormone receptor on plasma membrane integrin alphavbeta3. Via interaction with the integrin, tetrac is also capable of inhibiting the angiogenic effects of vascular endothelial growth factor and basic fibroblast growth factor. MDA-MB-231 cells are estrogen receptor-negative human breast cancer cells shown to be responsive to tetrac in terms of decreased cell proliferation. Here we describe actions initiated at the cell surface receptor by unmodified tetrac and nanoparticulate tetrac on a panel of survival pathway genes in estrogen receptor-negative human breast cancer (MDA-MB-231) cells. Nanoparticulate tetrac is excluded from the cell interior. Expression of apoptosis inhibitors XIAP (X-linked inhibitor of apoptosis) and MCL1 (myeloid cell leukemia sequence 1) was downregulated by nanoparticulate tetrac in these breast cancer cells whereas apoptosis-promoting CASP2 and BCL2L14 were upregulated by the nanoparticulate formulation. Unmodified tetrac affected only XIAP expression. Expression of the angiogenesis inhibitor thrombospondin 1 (THBS1) gene was increased by both formulations of tetrac, as was the expression of CBY1, a nuclear inhibitor of catenin activity. The majority of differentially regulated Ras-oncogene family members were downregulated by nanoparticulate tetrac. The latter downregulated expression of epidermal growth factor receptor gene and unmodified tetrac did not. Nanoparticulate tetrac has coherent anti-cancer actions on expression of differentially-regulated genes important to survival of MDA-MB-231 cells.

The pro-apoptotic action of stilbene-induced COX-2 in cancer cells: convergence with the anti-apoptotic effect of thyroid hormone.

Constitutively expressed cyclooxygenase-2 (COX-2) is a marker of tumor cell aggressiveness. Inducible COX-2 has also been described in cancer cells and localizes in the cancer cell nucleus, where formation of a complex of mitogen-activated protein kinase (MAPK) and COX-2 is antecedent to p53-dependent apoptosis. The stilbene resveratrol is a model pharmacologic activator of this pro-apoptotic mechanism. Physiological concentrations of thyroid hormone are anti-apoptotic in several types of tumor cells. A mechanism by which the hormone is anti-apoptotic is disruption of the nuclear MAPK-COX-2 complex. We review here the apoptosis-relevant effects of resveratrol and thyroid hormone and then speculate about the significance of convergence of these actions in cancer cells in the intact organism. Clinical activity of resveratrol may be modulated by normal tissue levels of endogenous thyroid hormone, and hypothyroidism in the cancer patient -- whether spontaneous or induced by chemotherapeutic agents -- may permit full expression of the apoptotic activity of the administered stilbene. Chronic pharmacologic inhibition of COX-2 may oppose the pro-apoptotic effect of resveratrol.