Decreased mitochondrial transcription factor A and mitochondrial DNA copy number promote cyclin-dependent kinase inhibitor 1A expression and reduce tumorigenic properties of colorectal cancer cells

Jessika Buchwaldt; Tania Fritsch; Monika Hartmann; Hagen Roland Witzel; Michael Kloth; Wilfried Roth; Katrin E Tagscherer; Nils Hartmann

doi:10.1007/s12672-024-01538-4

Decreased mitochondrial transcription factor A and mitochondrial DNA copy number promote cyclin-dependent kinase inhibitor 1A expression and reduce tumorigenic properties of colorectal cancer cells

Discov Oncol. 2024 Nov 24;15(1):701. doi: 10.1007/s12672-024-01538-4.

Authors

Jessika Buchwaldt¹, Tania Fritsch¹, Monika Hartmann², Hagen Roland Witzel¹, Michael Kloth¹, Wilfried Roth¹, Katrin E Tagscherer¹, Nils Hartmann³

Affiliations

¹ Institute of Pathology, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany.
² Department of Medicine III, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany.
³ Institute of Pathology, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany. nils.hartmann@unimedizin-mainz.de.

Abstract

Purpose: Colorectal cancer is one of the most common and deadliest cancer types worldwide. In the last years, changes in the mitochondrial DNA (mtDNA) copy number have been described to correlate with the prognostic outcome for colorectal cancer patients by impacting different tumorigenic properties. One key regulator of mtDNA is the mitochondrial transcription factor A (TFAM) that acts as a limiting factor of mtDNA copy number. Here, we investigated the effect of TFAM deficiency on mtDNA and tumorigenic properties in the human colorectal cancer cell line SW480.

Methods: TFAM expression was stably downregulated in the colorectal cancer cell line SW480 using the CRISPR-Cas9 approach. To dissect the molecular alterations induced by deletion of TFAM, RNA sequencing and gene set enrichment analysis was performed on TFAM-wild-type and TFAM-deficient SW480 cells. Functional consequences of TFAM downregulation were assessed in cellular assays.

Results: We showed that TFAM deficiency leads to decreased mtDNA copy number and reduced expression of mtDNA-encoded genes. TFAM-deficient cells also revealed higher activity of senescence-associated β-galactosidase and decreased cell growth parameters. Moreover, RNA sequencing showed that the expression of cyclin dependent kinase inhibitor 1A (CDKN1A/p21) is significantly increased in TFAM-deficient cells.

Conclusion: Our results suggest that TFAM-induced changes of the mitochondrial genome lead to upregulated CDKN1A/p21 expression in colorectal cancer cells identifying p21 as a new possible linker between mitochondria and nucleus.

Keywords: Cell proliferation; Colon cancer; Cyclin-dependent kinase inhibitor 1A (CDKN1A/p21); Mitochondria; Mitochondrial DNA (mtDNA); Senescence; Transcription factor A mitochondrial (TFAM).