Optimization of Invasion-Specific Effects of Betulin Derivatives on Prostate Cancer Cells through Lead Development.

Ville Härmä,Hannu-Pekka Schukov,Kirsi-Marja Oksman-Caldentey,Heiko Rischer,Ilmari Ahonen,Sami Alakurtti,Vânia M Moreira,Jari Yli-Kauhaluoma,Raisa Haavikko,Enkhee Purev,Johannes Virtanen,Matthias Nees

doi:10.1371/journal.pone.0126111

Abstract

The anti-invasive and anti-proliferative effects of betulins and abietane derivatives was systematically tested using an organotypic model system of advanced, castration-resistant prostate cancers. A preliminary screen of the initial set of 93 compounds was performed in two-dimensional (2D) growth conditions using non-transformed prostate epithelial cells (EP156T), an androgen-sensitive prostate cancer cell line (LNCaP), and the castration-resistant, highly invasive cell line PC-3. The 25 most promising compounds were all betulin derivatives. These were selected for a focused secondary screen in three-dimensional (3D) growth conditions, with the goal to identify the most effective and specific anti-invasive compounds. Additional sensitivity and cytotoxicity tests were then performed using an extended cell line panel. The effects of these compounds on cell cycle progression, mitosis, proliferation and unspecific cytotoxicity, versus their ability to specifically interfere with cell motility and tumor cell invasion was addressed. To identify potential mechanisms of action and likely compound targets, multiplex profiling of compound effects on a panel of 43 human protein kinases was performed. These target de-convolution studies, combined with the phenotypic analyses of multicellular organoids in 3D models, revealed specific inhibition of AKT signaling linked to effects on the organization of the actin cytoskeleton as the most likely driver of altered cell morphology and motility.

Highlights

Apart from skin cancer, prostate cancer (PrCa) is the most common cancer in men, especially in Europe
A set of 76 betulin derivatives was prepared starting from betulin and betulinic acid (1), whereas 13 derivatives were prepared from dehydroabietic acid and dehydroabietylamide (Figs 1–3, see S1 File), using our expertise on natural products chemistry and following either our previously reported procedures or those of others [34,35,36,37]
A free carboxyl group at C28 was important for their activity, which was considerably improved when compared to the parent betulinic acid

Summary

Introduction

Apart from skin cancer, prostate cancer (PrCa) is the most common cancer in men, especially in Europe. Early-stage PrCa can be successfully managed by operation alone and recurrent tumors are treated by ablation of circulating androgens by chemical castration. Late-stage castration-resistant PrCa (CRPC) with characteristic metastatic dissemination of the primary tumor, usually to the bone, remains the major cause of cancer-associated death. Significant progress has been made in the treatment of primary and androgen-sensitive prostate tumors, curative therapies that target the metastatic spread of advanced and aggressive CRPC currently do not exist. This is related to the lack of experimental model systems that faithfully represent the features of invasiveness and cell motility in vitro or in vivo

Methods

Results

Conclusion