Large tumor suppressor kinase 2 overexpression attenuates 5-FU-resistance in colorectal cancer via activating the JNK-MIEF1-mitochondrial division pathway

Background: 5-Fluorouracil (5-FU) is a standard treatment for colorectal cancer, but most patients develop 5-FU resistance. Here, we conducted experiments to identify an effective approach to augment 5-FU-based treatment in colorectal cancer in vitro. Methods: SW480 cells were in the present study and treated with 5-FU. Besides, LATS2 adenovirus vectors were infected into SW480 cells. Western blotting, immunofluorescence and ELISA were used to evaluate cell death and mitochondrial function. Pathway blocker was used to verify the role of MAPK-JNK pathway in SW480 cell death. Results: An obvious drop in large tumor suppressor kinase 2 (LATS2) expression was observed in SW480 cells after treatment with 5-FU. In addition, upregulation of LATS2 expression through infection with LATS2 adenovirus further increased the reduction of SW480 cell viability induced by 5-FU. Functional exploration showed that 5-FU treatment suppressed mitochondrial membrane potential, enhanced cyt-c release into the nucleus, induced an oxidative injury environment by promoting ROS production, and eventually upregulated Bax-related mitochondrial apoptosis. Besides, LATS2 overexpression in combination with 5-FU treatment further perturbed mitochondrial homeostasis, and this effect was achieved by elevating mitochondrial division. Mechanistically, LATS2 overexpression and 5-FU co-treatment amplified mitochondrial division by upregulating MIEF1 expression in a manner dependent on MAPK-JNK axis. Knockdown of MIEF1 using an siRNA-mediated loss of function assay and/or inhibition of the MAPK-JNK pathway using the specific inhibitor SP600125 abolished LATS2/5-FU-mediated deleterious effects on mitochondrial performance and SW480 cell viability. Conclusions: In light of the above findings, LATS2 downregulation could be a potential mechanism of low response to 5-FU treatment. Overexpression of LATS2 to further disrupt mitochondrial function via the JNK-MIEF1 signalling pathway might be a method to optimize 5-FU-based chemotherapy.