Pharmacological targeting of GLI1 inhibits proliferation, tumor emboli formation and in vivo tumor growth of inflammatory breast cancer cells

Abstract

Activation of the Hedgehog (Hh) pathway effector GLI1 is linked to tumorigenesis and invasiveness in a number of cancers, with targeting of GLI1 by small molecule antagonists shown to be effective. We profiled a collection of GLI antagonists possessing distinct mechanisms of action for efficacy in phenotypic models of inflammatory and non-inflammatory breast cancer (IBC and non-IBC) that we showed expressed varying levels of Hh pathway mediators. Compounds GANT61, HPI-1, and JK184 decreased cell proliferation, inhibited GLI1 mRNA expression and decreased the number of colonies formed in TN-IBC (SUM149) and TNBC (MDA-MB-231 and SUM159) cell lines. In addition, GANT61 and JK184 significantly down-regulated GLI1 targets that regulate cell cycle (cyclin D and E) and apoptosis (Bcl2). GANT61 reduced SUM149 spheroid growth and emboli formation, and in orthotopic SUM149 tumor models significantly decreased tumor growth. We successfully utilized phenotypic profiling to identify a subset of GLI1 antagonists that were prioritized for testing in in vivo models. Our results indicated that GLI1 activation in TN-IBC as in TNBC, plays a vital role in promoting cell proliferation, motility, tumor growth, and formation of tumor emboli.

The study of establishment of an in vivo tumor model by three-dimensional cells culture systems methods and evaluation of antitumor effect of biotin-conjugated pullulan acetate nanoparticles

“…Tumor formation and development are dynamic processes where cancer cells differentiate, proliferate and migrate interacting among each other and with the surrounding 3D environment in vivo. 40 Cancer cells in 3D culture system closely mimic pathologic events of tumors formation were reported. 34,41,42 HeG2 cells in 3D more easily self-assemble into spheroids, and then spheroids reproduce morphology and biologic properties of tumors tissue.…”

GLI1‐induced mammary gland tumours are transplantable and maintain major molecular features

“…However, RNA in situ and gene expression analyses did not suggest high expression levels of endogenous Gli1 and treating the serially transplanted tumours with the GLI1 inhibitor GANT61 did not result in statistically significant inhibition of tumour growth. Previously, breast cancer cell lines have been shown to be sensitive to GANT61 . The observed difference might depend on biological variations between the model systems.…”

“…Previously, breast cancer cell lines have been shown to be sensitive to GANT61. 7 The observed difference might depend on biological variations between the model systems. In our models, elevated GLI1 expression contributed to tumour initiation, for example, by inducing genetic instability and somatic mutations, and subsequent tumour growth and progression is driven by these primary genetic events.…”

“…GLI1 and PTCH1 are themselves transcriptional targets of GLI2 and GLI3. Activation of GLI1 may also be mediated via noncanonical pathways and is therefore resistant to currently clinically approved Hh pathway inhibitors, but shows sensitivity to the GLI1 inhibitor GANT61 . Components of the Hh signalling pathway are expressed in normal mammary gland stem/progenitor cells, as well as in tumour cells able to regenerate the parental tumour in transplantation assays (so‐called cancer stem cells, CD44 + CD24 ‐/low Lin − ) .…”

“…Activation of GLI1 may also be mediated via noncanonical pathways and is therefore resistant to currently clinically approved Hh pathway inhibitors, 3,5 but shows sensitivity to the GLI1 inhibitor GANT61. 6,7 Components of the Hh signalling pathway are expressed in normal mammary gland stem/progenitor cells, as well as in tumour cells able to regenerate the parental tumour in transplantation assays (so-called cancer stem cells, CD44 + CD24 -/low Lin − ). 8 GLI1 expression stimulated tumour initiation of TNBC 9 and a role for GLI1 in breast cancer is supported by data showing that increased GLI1 expression was associated with worse outcome in oestrogen receptor α negative (ER α − ) breast cancers.…”