tRNA modifications are required for stress granule formation and melanoma metastasis
Metastasis is the leading cause of cancer related deaths, however therapies specifically targeting metastasis are lacking and remain a dire therapeutic need in the clinic. Metastasis is a highly inefficient process that is inhibited by extracellular stress. Therefore, metastasizing cells that ultimately survive and successfully colonize distant organs must undergo molecular rewiring to mitigate stress. Wobble uridine modifications, especially 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U34), have been implicated in stress response and poor prognosis of cancer patients. We use a patient derived xenograft (PDX) model of melanoma metastasis to study the role of the mcm5s2U34 modification in the stress response of metastasizing cells. We find that upon depletion of elongator acetyltransferase complex subunit 1 (ELP1)-- a component of the mcm5s2U34 pathway on [Formula], and [Formula] --codon-biased translation, migration, invasion, and metastatic burden in vivo is reduced. Further, we observe that stress granule components are enriched in a subset of codon-biased genes that are exclusively upregulated at the protein level in metastatic nodules compared to the primary tumor in our PDX model. Additionally, upon knockdown of ELP1, stress granule components have decreased protein expression with no significant change to their mRNA levels. Efficient translation, mediated by the carboxy-methylation arm of the mcm5s2U34 modification, is required for metastasizing cancer cells to withstand stress via stress granule formation and increase survival throughout the metastatic cascade. This makes the mcm5s2U34 machinery a potentially actionable therapeutic target, specific to metastatic disease.