Molecular detection of PPAR gamma rearrangements and thyroid carcinoma in preoperative fine-needle aspiration biopsies.

The pathologic diagnosis of thyroid follicular tumors is difficult, particularly in preoperative fine-needle aspiration biopsies. To investigate whether the molecular diagnosis of PPAR gamma rearrangements can detect thyroid carcinomas in fine-needle aspiration biopsies, we performed interphase fluorescence in situ hybridization on 24 thyroid fine-needle aspiration and 17 follow-up thyroidectomy specimens. Two of the 24 fine-needle aspiration biopsies contained PPAR gamma rearrangements, and both were diagnosed suggestive of a thyroid follicular neoplasm by cytology. The two corresponding thyroidectomies each contained PPAR gamma rearrangements in all tumor cells and, both were diagnosed follicular-patterned thyroid carcinomas-one a follicular carcinoma and the other a follicular variant of papillary carcinoma, the latter by majority of expert endocrine pathologists. Our experiments demonstrate that PPAR gamma rearrangements can detect a subset of follicular-patterned thyroid carcinomas in preoperative thyroid fine-needle aspiration biopsies. The ultimate utility of mutations such as PPAR gamma rearrangements in diagnosis of thyroid carcinoma must be proven by direct correlation of mutation status with thyroid tumor biology and not just with thyroid tumor morphology, a subjective and imprecise marker of clinical behavior. The application of specific mutations to preoperative diagnosis of thyroid carcinoma is predicted to improve the accuracy and reduce the costs of treating patients with thyroid tumors.

Functional characterization of telomerase RNA variants found in patients with hematologic disorders.

Human telomerase uses a specific cellular RNA, called hTERC, as the template to synthesize telomere repeats at chromosome ends. Approximately 10% to 15% of patients with aplastic anemia or other bone marrow failure syndromes are carriers of hTERC sequence variants whose functional significance, in most cases, is unknown. We screened 10 reported and 2 newly discovered hTERC variants from such patients and found that 10 of these negatively affected telomerase enzymatic function when they were used to reconstitute telomerase enzymatic function in human cells. Most functional deficits were due to perturbations of hTERC secondary structure and correlated well with the degrees of telomere shortening and reduced telomerase activity observed in peripheral blood lymphocytes of the representative patients. We also found no evidence of dominant-negative activity in any of the mutants. Therefore, loss of telomerase activity and of telomere maintenance resulting from inherited hTERC mutations may limit marrow stem cell renewal and predispose some patients to bone marrow failure.

PIKE-A is amplified in human cancers and prevents apoptosis by up-regulating Akt.

PIKE-A (PIKE-activating Akt), an isoform of PIKE GTPase that enhances phosphatidylinositol 3-kinase (PI3-kinase) activity, specifically binds to active Akt but not PI3-kinase. PIKE-A stimulates Akt activity in a GTP-dependent manner and promotes invasiveness of cancer cell lines. Here, we show that PIKE-A is amplified in a variety of human cancers and that amplified PIKE-A directly stimulates Akt and inhibits apoptosis compared to cells with normal PIKE-A copy number. Overexpression of PIKE-A wild-type but not dominant-negative mutant stimulates Akt activity and prevents apoptosis. Moreover, knockdown of PIKE-A diminishes Akt activity and increases apoptosis. Our findings suggest that PIKE-A amplification contributes to cancer cell survival and progression by inhibiting apoptosis through up-regulating Akt.