Lesson 7: RB (Retinoblastoma), a children's eye cancer, could be treated by PAK1-blockers such as propolis

Loss or dysfunction of tumor suppressor RB gene causes a rare eye cancer, during an early childhood, called retinoblastoma (RB). So far no effective therapeutics has been developed. However, recently a team in Puerto Rico and USA jointly discovered the very first clue to the potentially effective RB therapy.  They found that the transcription factor RB represses the expression of oncogenic/ ageing PAK1 gene (1).  In other words, blocking PAK1 over-expressed by loss of RB in retinoblastoma could lead to suppression of the growth of this eye cancer.  In the past (more than a decade ago) , butyrate, a HDAC (histone deacetylase) inhibitor, was shown to suppress the growth of RB (retinoblastoma) cells in cell culture, most likely by down-regulating two oncogenic kinases, AKT and PAK1. However, the IC50 of butyrate against HDAC is very high (above 1 mM), and therefore has never been used clinically. I believe a variety of far more effective PAK1-blockers (synthetic or herbal) such as propolis would be useful for treatment of retinoblastoma and many other PAK1-dependent cancers without any side effect. 

References:

1. Sosa-García B¹, Vázquez-Rivera V¹, González-Flores JN¹, Engel BE², Cress WD², Santiago-Cardona PG¹. The Retinoblastoma Tumor Suppressor (RB) Transcriptionally Represses Pak1 in Osteoblasts. PLoS One. 2015 Nov 10;10(11):e0142406.