AKAP12 is Upregulated by Base Deletion at Positions 61–78 in Exon 3, Leading to Suppressed Proliferation and Metastasis of Benzo[a]pyrene-Transformed HBE Cells

The carcinogenic mechanism of benzo[a]pyrene (BaP) is not fully understood. Our previous studies unexpectedly revealed that A-kinase anchoring protein 12 (AKAP12), a recognized tumor suppressor frequently downregulated in malignancies, is markedly upregulated in BaP-transformed 16HBE cells (THBEc1). This paradoxical upregulation prompted us to investigate its functional consequence and regulatory mechanism. Using CRISPR/Cas9-mediated genome editing, we serendipitously obtained a cell line harboring a homozygous 18-bp deletion at positions 61 to 78 in exon 3 of AKAP12, resulting in loss of six amino acids and sustained upregulation of mutant protein; this line was named THBEc1-ΔAKAP12-c4. These cells exhibited decreased in vitro colony growth and migration, and decreased in vivo experimental lung metastasis, without affecting subcutaneous tumor growth, revealing selective suppression of metastatic phenotypes. Furthermore, we identified forkhead box A1 (FOXA1), a transcription factor with an established oncogenic role in BaP-induced carcinogenesis, as a key upstream regulator: knockout of FOXA1 downregulated AKAP12. These findings outline a dual role for FOXA1 in driving oncogenic processes while upregulating AKAP12 as a compensatory brake on metastasis. Our study supports the tumor/metastasis suppressor role of AKAP12 in BaP-induced carcinogenesis, and the mutant AKAP12 provides a tool for dissecting the functional domains of this protein.