Daniela Piccin

miR-15a and miR-16-1 down-regulation in pituitary adenomas

Micro RNAs (miRs) are small noncoding RNAs, functioning as antisense regulators of other RNAs. miR‐15a and miR‐16‐1 genes are located at chromosome 13q14, a region which is frequently deleted in pituitary tumors. An inverse correlation has been shown in B cell chronic lymphocytic leukemia (B‐CLL) between miR‐15a and miR‐16‐1 expression and the expression levels of arginyl‐tRNA synthetase (RARS), an enzyme which associates with the cofactor p43 in the aminoacyl‐tRNA synthetase complex. When secreted, p43 regulates local inflammatory response and macrophage chemotaxis, and seems to have anti‐neoplastic properties in mice. We explored miR‐15a and miR‐16‐1 expression in 10 GH‐secreting and in 10 PRL‐secreting pituitary macroadenomas by Northern blot, and investigated the possible correlation with in vivo and in vitro characteristics. We found that miR‐15a and miR‐16‐1 are expressed at lower levels in pituitary adenomas as compared to normal pituitary tissue. Moreover, their expression inversely correlates with tumor diameter and with RARS expression (P < 0.05), but directly correlates with p43 secretion (P < 0.02). Therefore, miR15 and miR16 down‐regulation in pituitary adenomas correlates with a greater tumor diameter and a lower p43 secretion, suggesting that these genes may, at least in part, influence tumor growth.

Identification of differentially expressed microRNAs by microarray: A possible role for microRNA genes in pituitary adenomas

MicroRNAs (miRNAs) are small non‐coding RNAs that control gene expression by targeting mRNA. It has been demonstrated that miRNA expression is altered in many human cancers, suggesting that they may play a role in human neoplasia. To determine whether miRNA expression is altered in pituitary adenomas, we analyzed the entire miRNAome in 32 pituitary adenomas and in 6 normal pituitary samples by microarray and by Real‐Time PCR. Here, we show that 30 miRNAs are differentially expressed between normal pituitary and pituitary adenomas. Moreover, 24 miRNAs were identified as a predictive signature of pituitary adenoma and 29 miRNAs were able to predict pituitary adenoma histotype. miRNA expression could differentiate micro‐ from macro‐adenomas and treated from non‐treated patient samples. Several of the identified miRNAs are involved in cell proliferation and apoptosis, suggesting that their deregulated expression may be involved in pituitary tumorigenesis. Predictive miRNAs could be potentially useful diagnostic markers, improving the classification of pituitary adenomas. J. Cell. Physiol. 210: 370–377, 2007.

Cyclooxygenase-2 inhibitors prevent the development of chemoresistance phenotype in a breast cancer cell line by inhibiting glycoprotein p-170 expression

Breast cancer cells are usually sensitive to several chemotherapeutic regimens, but they can develop chemoresistance after prolonged exposure to cytotoxic drugs, acquiring a more aggressive phenotype. Drug resistance might involve the multi-drug resistance (MDR) 1 gene, encoding a transmembrane glycoprotein p-170 (P-gp), which antagonizes intracellular accumulation of cytotoxic agents, such as doxorubicin. We previously demonstrated that type 2 cyclooxygenase (COX-2) inhibitors can reverse the chemoresistance phenotype of a medullary thyroid carcinoma cell line by inhibiting P-gp expression and function. The aim of our study was to investigate the role of COX-2 inhibitors in modulating chemoresistance in a human breast cancer cell line, MCF7. MCF7 cells, expressing COX-2 but not MDR1, were treated with increasing doses of doxorubicin, and they became chemoresistant after 10 days of treatment, in association with MDR1 expression induction. This effect was reversed by doxorubicin withdrawal and prevented by co-incubation with N-[2-(cyclohexyloxy)4-nitrophenyl]-methanesulfonamide (NS-398), a selective COX-2 inhibitor. Treatment with NS-398 alone did not influence cell viability of a resistant MCF7 cell clone (rMCF7), but sensitized rMCF7 cells to the cytotoxic effects of doxorubicin. Moreover, treatment with NS-398 significantly reduced MDR1 expression in rMCF7 cells. Doxorubicin-induced membrane P-gp expression and function was also greatly impaired. Our data therefore support the hypothesis that COX-2 inhibitors can prevent or reduce the development of the chemoresistance phenotype in breast cancer cells by inhibiting P-gp expression and function.

Antiproliferative effects of somatostatin analogs in pituitary adenomas.

The antisecretory effects of somatostatin (SRIF) and its analogs are widely recognised and provide the basis for treatment of hormonal hypersecretion in pituitary adenomas, especially in the settings of acromegaly. Evidence for an antiproliferative effect of these compounds has also been provided.This review focuses on the mechanisms transducing the antiproliferative effects of SRIF and its analogs on pituitary adenomas, and on the clinical consequences on tumor volume of pharmacological treatment of pituitary adenomas with these drugs.

Proteasomes and RARS modulate AIMP1/EMAP II secretion in human cancer cell lines

The aminoacyl t‐RNA synthetase interacting multifunctional protein (AIMP1) is the precursor of the multifunctional inflammatory cytokine endothelial monocyte‐activating polypeptide II (EMAP II). We previously demonstrated that AIMP1 secretion by pituitary adenomas is inversely correlated with tumor diameter and with RARS expression, suggesting that a high amount of RARS associated with AIMP1 might prevent the secretion of the latter cytokine. In this study, we investigated the role of RARS in modulating the secretion of AIMP1 in HeLa and MCF7 cell lines and investigated the possible role of the multicatalytic protease in the cleavage of AIMP1 to generate EMAP II. Our data show that RARS over‐expression impairs AIMP1 secretion by both HeLa and MCF7 cells. Moreover, proteasome inhibition impairs AIMP1 cleavage to produce EMAP II. These data indicate that RARS over‐expression associates with a reduced AIMP1 secretion and that the multicatalytic protease is involved in the generation of the mature cytokine, EMAP II. J. Cell. Physiol. 212: 293–297, 2007.