A review and perspective paper: Ras oncogene gets modest, from kingpin to mere henchman

The concomitant activation of both the YAP1 co-transcription factor and RAS GTPases is a hallmark of several aggressive cancers, though the intricacies of their relationship and implications for oncogenesis are still poorly understood. This review has presented a cooperative model where YAP1 and RAS are not independently acting oncogenes but rather interdependently acting ones, with each fulfilling an essential role within the oncogenic process. YAP1 is responsible for initiating the expression of key proteins that contribute to various cancer traits. However, these proteins must often be transported into the cytoplasm to exert their effects. We suggest that oncogenic RAS actually facilitates this transport, enabling the phosphorylation and subsequent activation of the nuclear transporter XPO1 (aka Exportin1). This mechanism is particularly crucial for anti-apoptotic proteins. Instead of being sequestered within the nucleus in an ineffective state, these proteins are rather shuttled into the cytoplasm. Within the cytoplasm, they can effectively inhibit apoptosis, undermining by these means the efficacy of chemotherapeutic agents designed to induce cell death in cancer cells. Therefore, a clearer understanding of the oncogenic partnership between RAS and YAP1 will likely provide new insights into the molecular underpinnings of cancer and highlight as well potential targets for therapeutic interventions designed to disrupt this pernicious interaction. Graphical Abstract: I. YAP1 triggers expression of its target genes, some of which encode cargoes with a nuclear export signal. In response to physiological signals, some cargoes are shuttled into the cytoplasm. Exportin1 serves as the transfer vehicle from the nucleus into the cytoplasm (not shown). For functional nuclear proteins, this shuttling terminates their function, whereas for cytoplasmic proteins, it does initiate their function. In this drawing, the topology within the nucleus is not depicted. II. Oncogenic RAS leads to Exportin1 activation and subsequent unwarranted nuclear-cytoplasmic shuttling of cargoes [17, 35]. The cascade from RAS to Exportin1 is not depicted for the sake of clarity. Some of the cargoes are oncoproteins, cytoplasmic GTPases regulators, or antiapoptotic proteins (example shown: BIRC5 aka Survivin). These latter proteins are now empowered to hinder apoptosis, as expected upon anti-cancer therapies. Of course, the BIRC5 is not the only aberrantly shuttled protein. Another example is Beclin1 (BECN1), which is subjected to the same fate; once in the cytoplasm, it does initiate autophagy in the absence of any autophagic clue [35]. (Figure presented.).