MCU That Is Transcriptionally Regulated by Nrf2 Augments Malignant Biological Behaviors in Oral Squamous Cell Carcinoma Cells

Abstract

Objective. To clarify the role and molecular mechanism of mitochondrial calcium uniporter (MCU) in the malignant biological behaviors of oral squamous cell carcinoma (OSCC) cells through clinical and cellular experiments. Methods. Immunohistochemistry and qRT-PCR techniques were used to observe the expression of MCU, nuclear factor erythroid 2-related factor 2 (Nrf2), mitochondrial calcium uptake 1 (MICU1), and MICU2 in OSCC and normal tissues. After treatment with si-MCU, spermine, and/or sh-Nrf2, malignant biological behaviors of OSCC cells including proliferation, migration, and apoptosis were detected by clone formation, migration, and mitochondrial membrane potential (MMP) assays. Furthermore, MCU, MICU1, MICU2, Nrf2, and other proteins related to malignant biological behaviors were examined using western blot, immunohistochemistry, and immunofluorescence assays. Results. MCU, Nrf2, and MICU1 were strongly expressed in OSCC as compared to normal tissues, while MICU2 was relatively weakly expressed in OSCC tissues. Knockdown of MCU distinctly weakened proliferation and migration and lowered MMP level in CAL 27 cells. Conversely, its activation reinforced migrated capacity and increased MMP level in CAL 27 cells, which was reversed after cotransfection with sh-Nrf2. After treatment with si-MCU or spermine, Nrf2 expression was not affected in CAL 27 cells. However, MCU expression was distinctly suppressed in CAL 27 cells transfected with sh-Nrf2. Furthermore, knockdown of Nrf2 significantly reversed the increase in expression of MICU1 and MICU2 induced by MCU activation in CAL 27 cells. Conclusion. MCU, as a novel oncogene of OSCC, augments malignant biological behaviors of OSCC cells, which could be transcriptionally regulated by Nrf2.

The mitochondrial Ca2+channel MCU is critical for tumor growth by supporting cell cycle progression and proliferation

“…In previous studies, including our own, acute deletion or knockdown of MCU had significant effects on mitochondrial energy metabolism (Cardenas et al, 2016;Tosatto et al, 2016;Ren et al, 2017;Stejerean-Todoran et al, 2022). However, chronic deletion of MCU has been observed to not result in overt changes of basal mitochondrial metabolism (Pan et al, 2013;Kwong et al, 2015;Luongo et al, 2015;Hamilton et al, 2018;Koval et al, 2019;Wu et al, 2021). Discrepancies between chronic and acute MCU knockout/knockdown models is a recurring theme that might be explained by the activation of compensatory adaptations to maintain mitochondrial energy metabolism (Garbincius and Elrod, 2022).…”

“…Furthermore, maintenance of quiescence and escape of hematopoietic stem cells (HSC) from quiescence requires mitochondrial Ca 2+ uptake (Resende et al, 2010;Umemoto et al, 2018;Ahumada-Castro et al, 2021;Paliwal et al, 2021). Inhibition of cell proliferation by MCU-KO is consistent with anti-proliferative effects of MCU suppression in cancer cells (Cardenas et al, 2016;Ren et al, 2017;Li et al, 2020b;Liu et al, 2020;Wang et al, 2020;Miao et al, 2021;Wu et al, 2021;, although this has not been universally observed (Curry et al, 2013;Hall et al, 2014;Tosatto et al, 2016;Young et al, 2022). Despite slower tumor growth in xenografts, proliferation in vitro of several breast cancer cell lines were independent of MCU (Tosatto et al, 2016), and it has been reported that stable deletion of MCU in HEK293T and HeLa cell lines resulted in enhanced cell proliferation (Young et al, 2022).…”

The Regulatory Roles of Mitochondrial Calcium and the Mitochondrial Calcium Uniporter in Tumor Cells

“…The MCU is a new proto-oncogene of OSCC, which is regulated by nuclear factor erythroid 2-related factor 2 (Nrf2) transcription. The MCU can enhance the proliferation of OSCC cells and inhibit apoptosis [ 142 ]. Dihydroartemisinin can repress the proliferation and migration of OSCC cells by inhibiting the expression of the MCU [ 143 ].…”

Roles of Mitochondria in Oral Squamous Cell Carcinoma Therapy: Friend or Foe?

“…Although these studies did not reveal the direct role of mitochondria in these processes, considering the importance of mitochondria in metabolism, mitochondria, undoubtedly also play a multitude of roles in OSCC. For example, mitochondrial calcium uniporter was strongly expressed in OSCC compared with normal tissues, and the downregulation of mitochondrial calcium uniporter expressly impaired the proliferation and migration of OSCC cells [ 40 ]. The oxidation of nicotinamide adenine dinucleotide (NADH), a lactate derivative from cancer-associated fibroblasts (CAFs), in the mitochondrial oxidative phosphorylation (OXPHOS) of OSCC cells could promote the proliferation of OSCC [ 41 ].…”