The Hsp32/H0-1-Targeted Drug Sma-Znpp Counteracts The Proliferation And Viability Of Neoplastic Cells In Solid Tumors And Hematologic Neoplasms

14122 Background: Heat shock protein 32 (Hsp32) is a stress-related survival factor that is overexpressed in various neoplastic cells. Recently, specific Hsp32- targeting drugs such as styrene maleic acid encapsulated zinc protoporphyrin (SMA-ZnPP) have been developed. Methods: We examined the effects of SMA-ZnPP on proliferation and survival of various tumor cell-lines, including U97MG (glioblastoma), A549 (lung cancer), MDA-MB-231 (breast cancer), BxPC-3 (pancreatic), HepG2 (hepatocellular), Colo201, Colo320DM, DLD-1 (colon), OvCar3 (ovarian carcinoma), KG1, U937, HL60, K562 (myeloid leukemias), RAJI, NALM-6 (lymphatic leukemias), RPMI 8226, U266 (multiple myeloma) as well as on primary neoplastic cells. Moreover, Ba/F3 cells with doxycycline-inducible expression of oncoproteins (RAS-G12V, BCR/ABL, KIT-D816V) were analyzed. Expression of Hsp32 mRNA was examined by RT-PCR and Northern blotting, and expression of the Hsp32 protein by Western blotting. To silence Hsp32 in neoplastic cells, we used specific siRNA as well as SMA-ZnPP. Proliferation was analyzed by 3H-thymidine uptake and apoptosis by light microscopy. Results: All neoplastic cells tested were found to express Hsp32 mRNA and the Hsp32 protein in a constitutive manner. In Ba/F3 cells, induction of RAS-G12V, BCR/ABL, or KIT D816V enhanced the expression of Hsp32. The Hsp32 siRNA was found to lead to a reduced viability and induction of apoptosis. Treatment of malignant cells with SMA-ZnPP resulted in a significant decrease in proliferation and induction of apoptosis. The effects of SMA- ZnPP on primary neoplastic cells and cell lines were dose-dependent and occurred at pharmacologic concentrations (IC50 1–30 μM). Moreover, SMA-ZnPP was found to synergize with various anti-neoplastic drugs (cisplatin, cytarabine, tyrosine kinase inhibitors, bortezomib) in producing growth-inhibition in neoplastic cells. Conclusions: The Hsp32-targeting drug SMA-ZnPP counteracts malignant cell growth and sensitizes neoplastic cells against various other targeted or conventional antineoplastic drugs. Hsp32-targeting drugs may represent an interesting new aproach to inhibit malignant cell growth in solid tumors and leukemias. No significant financial relationships to disclose.