Additive Effects of Retinoic Acid (RA) and Bone Morphogenetic Protein 4 (BMP-4) Apoptosis Signaling in Retinoblastoma Cell Lines

Abstract

Retinoids have been shown to serve promising therapeutic agents for human cancers, e.g. the treatment of neuroblastoma. Synthetic retinoids, specific for particular retinoic acid (RA) receptors, are tested as new therapy strategies. In the present study, application of recombinant retinoic acid (RA) lowers retinoblastoma (RB) cell viability and induces apoptosis in RB cell lines. Combined treatment of RA and bone morphogenetic protein 4 (BMP-4) increases the pro-apoptotic effect of RA in the RB cells lines WERI-Rb1, Y-79, RB355, RBL-30 and RBL-15, indicating an additive effect. We could show that in WERI-Rb1 cells RA/BMP-4 mediated cell death is at least partially caspase-dependent, whereby RA and BMP-4 additively increased (i) Apaf-1 mRNA levels, (ii) caspase-9 cleavage activity and (iii) the number of activated, cleaved caspase-3 positive cells. Compared to single application of RA and BMP-4, combined RA/BMP-4 treatment significantly augments mRNA levels of the retinoic acid receptors (RARs) RARα and RARß and the retinoic X receptor (RXR) RXRγ suggesting an interaction in the induction of these RA receptor subtypes in WERI-Rb1 cells. Agonist studies revealed that both, RARs and RXRs are involved in RA/BMP-4 mediated apoptosis in WERI-Rb1 retinoblastoma cells. Employing specific RAR subtype antagonists and a RXRß and RXRγ knockdown, we proved that RA/BMP-4 apoptosis signaling in WERI-Rb1 cells requires the RA receptor subtypes RARα, RARß, RXRß and RXRγ. Deciphering signaling mechanisms underlying apoptosis induction of RA and BMP-4 in WERI-Rb1 cells, our study provides useful starting-points for future retinoid-based therapy strategies in retinoblastoma.

Surface marker profiling of SH-SY5Y cells enables small molecule screens identifying BMP4 as a modulator of neuroblastoma differentiation

“…These examples suggest elaborate intracellular signaling modulation that can lead to both additive, but also a putative inhibitory effect of BMP4 on RA signaling reflecting the complex interaction between the two signaling cascades at early and late stages of neural crest development 63 , 67 . Profound synergism of BMP4 and RA co-stimulation, leading to increased pro-apoptotic effects, have been previously reported in P19 embryonal carcinoma cells 67 and in retinoblastoma cell lines 64 . This suggests that perhaps a combinatorial, rather than sequential treatment strategy could potentially be more effective in NB cells as well.…”

“…In addition, cells within Cluster 1 were exclusively affected by exposure to BMP4, resulting in a decrease of this particular cellular subset. BMP-signaling is well known to play a major role at various stages during neural crest cell differentiation 63 and has been shown to promote cell death in certain tumors 64 . As illustrated by the longer neurite-like extensions seen in phase contrast microscopy (see Fig.…”

Impact of RARα and miR-138 on retinoblastoma etoposide resistance

“…Retinoic acid receptors alpha (RAR␣) plays a role in human tumors such as acute promyelocytic leukemia (APL), esophageal carcinoma [8] and retinoblastoma [9]. A PML-RAR␣ fusion protein can be found in most APL cases [10], in which a successful beneficial retinoid based therapy has been achieved in clinical evaluations [11].…”

“…A PML-RAR␣ fusion protein can be found in most APL cases [10], in which a successful beneficial retinoid based therapy has been achieved in clinical evaluations [11]. Moreover, RARs are involved in RA/BMP4 mediated induction of apoptosis in the human retinoblastoma cell line WERI-Rb1 [9].…”

Attenuation of Hypertrophy in Human MSCs via Treatment with a Retinoic Acid Receptor Inverse Agonist

“…According to these findings, RAR signaling in the late stage of chondrocyte maturation seems to be at least partially mediated by BMPs. In return, BMP4 treatment increases the gene expression of specific RAR and RXR subtypes [53]. With respect to these interactions between the RAR and the BMP pathway, it appears reasonable that inhibition of RAR signaling with BMS has an influence on BMP4 effects.…”