The TLK1–MK5 Axis Regulates Motility, Invasion, and Metastasis of Prostate Cancer Cells

Abstract

Background: Metastatic dissemination of prostate cancer (PCa) accounts for the majority of PCa-related deaths. However, the exact mechanism of PCa cell spread is still unknown. We uncovered a novel interaction between two unrelated promotility factors, tousled-like kinase 1 (TLK1) and MAPK-activated protein kinase 5 (MK5), that initiates a signaling cascade promoting metastasis. In PCa, TLK1–MK5 signaling might be crucial, as androgen deprivation therapy (ADT) leads to increased expression of both TLK1 and MK5 in metastatic patients, but in this work, we directly investigated the motility, invasive, and metastatic capacity of PCa cells following impairment of the TLK1 > MK5 axis. Results: We conducted scratch wound repair and transwell invasion assays with LNCaP and PC3 cells to determine if TLK1 and MK5 can regulate motility and invasion. Both genetic depletion and pharmacologic inhibition of TLK1 and MK5 resulted in reduced migration and invasion through a Matrigel plug. We further elucidated the potential mechanisms underlying these effects and found that this is likely due to the reorganization of the actin fibers at lamellipodia and the focal adhesions network, in conjunction with increased expression of some MMPs that can affect penetration through the ECM. PC3, a highly metastatic cell line when assayed in xenografts, was further tested in a tail-vein injection/lung metastasis model, and we showed that, following inoculation, treatment with GLPG0259 (MK5 specific inhibitor) or J54 (TLK1 inhibitor) resulted in the lung tumor nodules being greatly diminished in number, and for J54, also in size. Conclusion: Our data support that the TLK1–MK5 axis is functionally involved in driving PCa cell metastasis and clinical aggressiveness; hence, disruption of this axis may inhibit the metastatic capacity of PCa.

Characterizing intergenic transcription at RNA polymerase II binding sites in normal and cancer tissues

“…The first RNAPII-bound region is located between the genes TLK1 and METTL8 at 40 kb and 44 kb, respectively ( Figure 7 B). TLK1 has been linked to poor patient outcomes in multiple cancer types, including GBM 39 and prostate cancer metastasis, 40 , 41 and it is involved in DNA replication and chromatin assembly. 39 METTL8 has been identified as a potential biomarker in hepatocellular carcinoma, 42 and high levels have been associated with improved patient survival in pancreatic cancer.…”

Normal and cancer tissues are accurately characterised by intergenic transcription at RNA polymerase 2 binding sites

“…7c ). TLK1 has been linked to poor patient outcomes in multiple types of cancer, including Glioblastoma Multiforme 39 and Prostate cancer metastasis 40,41 , and is required for DNA replication and chromatin assembly 39 . METTL8 has been identified as a potential biomarker in Hepatocellular carcinoma 42 , and high levels have been linked to patient survival in Pancreatic cancer 43 .…”

Autophosphorylation of the Tousled-like kinases TLK1 and TLK2 regulates recruitment to damaged chromatin via PCNA interaction

“…There are ongoing efforts to develop TLK1 and TLK2 inhibitors for targeting cancer cells with their promising roles in maintaining genome stability (64)(65)(66). Emerging evidence demonstrated that TLK1 and TLK2 are involved in cancer progression and therapeutic resistance (67)(68)(69)(70) and it has been shown that inhibition of TLK potentiates cell-killing in different types of cancers (1,(70)(71)(72)(73)(74), making TLK 1 and 2 attractive targets for therapeutic strategy development.…”