Pyrazolo[3,4-d]pyrimidines c-Src inhibitors reduce epidermal growth factor-induced migration in prostate cancer cells

FYN is overexpressed in human prostate cancer

OBJECTIVE

To test the hypothesis that FYN, a member of the SRC family of kinases (SFKs), is up-regulated in prostate cancer, as FYN is functionally distinct from other SFKs, and interacts with FAK and paxillin (PXN), regulators of cell morphology and motility.

MATERIALS AND METHODS

Through data-mining in Oncomine (http://www.oncomine.org), cell-line profiling with immunoblotting, quantitative reverse transcription and polymerase chain reaction (RT-PCR) and immunohistochemical analysis, we described FYN expression in prostate cancer. The analysis included 32 cases of prostate cancer, nine of prostatic intraepithelial neoplasia (PIN) and 19 normal prostates. Samples were scored for the percentage of stained glands and intensity of staining (from 0 to 3). Each sample was assigned a composite score generated by multiplying percentage and intensity.

RESULTS

Data-mining showed an eight times greater FYN expression in prostate cancer than in normal tissue; this was specific to FYN and not present for other SFKs. Expression of FYN in prostate cancer cell lines (LNCaP, 22Rv1, PC3, DuPro) was detected using quantitative RT-PCR and immunoblotting. Expression of FYN and its signalling partners FAK and PXN was detected in human tissue. Comparing normal with cancer samples, there was a 2.1-fold increase in median composite score for FYN (P < 0.001) 1.7-fold increase in FAK (P < 0.001), and a doubling in PXN (P < 0.05). There was a 1.7-fold increase in FYN (P < 0.05) and a 1.6-fold increase in FAK (P < 0.01) in cancer compared with PIN.

CONCLUSIONS

These studies support the hypothesis that FYN and its related signalling partners are up-regulated in prostate cancer, and support further investigation into the role of the FYN as a therapeutic target.

Antiproliferative and proapoptotic activities of new pyrazolo[3,4-d]pyrimidine derivative Src kinase inhibitors in human osteosarcoma cells

Osteosarcoma is the most frequent primitive malignant tumor of the skeletal system, characterized by an extremely aggressive clinical course that still lacks an effective treatment. Src kinase seems to be involved in the osteosarcoma malignant phenotype. We show that the treatment of human osteosarcoma cell lines with a new pyrazolo[3,4-d]pyrimidine derivative Src inhibitor, namely SI-83, impaired cell viability, with a half-maximal inhibitory concentration of 12 microM in nonstarved cells and a kinetic different from that known for the Src inhibitor PP2. Analysis by terminal deoxynucleotidyl transferase-mediated nick end labeling, Hoechst, and flow cytometric assay showed that SI-83 induced apoptosis in SaOS-2 cells. Moreover, SI-83, by inhibiting Src phosphorylation, decreased in vivo osteosarcoma tumor mass in a mouse model. Finally, SI-83 showed selectivity for osteosarcoma, since it had a far lower effect in primary human osteoblasts. These results show that human osteosarcoma had Src-dependent proliferation and that modulation of Src activity may be a therapeutic target of this new compound with low toxicity for nonneoplastic cells.

Identification of a novel pyrazolo[3,4-d]pyrimidine able to inhibit cell proliferation of a human osteogenic sarcoma in vitro and in a xenograft model in mice

New pyrazolo[3,4-d]pyrimidines were synthesized and found to inhibit Src phosphorylation in a cell-free assay. Some of them significantly reduced the growth of human osteogenic sarcoma (SaOS-2) cells. The best compound, in terms of inhibitory properties toward both Src and SaOS-2 cells, was further investigated and found to reduce bone resorption when used to treat mouse osteoclasts, without interfering with normal osteoblast growth. Moreover, its metabolic stability prompted its study on a human SaOS-2 xenograft tumor model in nude mice, where the compound reduced significantly both the volume and weight of the tumor. These experimental findings make the new compound an interesting hit in the field of bone-related diseases.