We previously reported that overexpression of
cytochrome P450 family 24 subfamily A member 1 (
CYP24A1) increases
lung cancer cell proliferation by activating RAS signaling and that
CYP24A1 knockdown inhibits
tumor growth. However, the mechanism of CYP24A1-mediated
cancer cell proliferation remains unclear. Here, we conducted cell synchronization and biochemical experiments in
lung adenocarcinoma cells, revealing a link between
CYP24A1 and
anaphase-promoting complex (APC), a key cell cycle regulator. We demonstrate that
CYP24A1 expression is cell cycle-dependent; it was higher in the G2-M phase and diminished upon G1 entry.
CYP24A1 has a functional destruction box (D-box) motif that allows binding with two APC adaptors, CDC20-homologue 1 (CDH1) and cell division cycle 20 (CDC20). Unlike other APC substrates, however,
CYP24A1 acted as a pseudo-substrate, inhibiting CDH1 activity and promoting mitotic progression. Conversely, overexpression of a
CYP24A1 D-box mutant compromised CDH1 binding, allowing CDH1 hyperactivation, thereby hastening degradation of its substrates
cyclin B1 and CDC20, and accumulation of the CDC20 substrate p21, prolonging mitotic exit. These activities also occurred with a
CYP24A1 isoform 2 lacking the catalytic
cysteine (Cys-462), suggesting that
CYP24A1's oncogenic potential is independent of its catalytic activity.
CYP24A1 degradation reduced clonogenic survival of mutant KRAS-driven
lung cancer cells, and
calcitriol treatment increased
CYP24A1 levels and
tumor burden in Lsl-KRASG12D mice. These results disclose a catalytic activity-independent growth-promoting role of
CYP24A1 in mutant KRAS-driven
lung cancer. This suggests that
CYP24A1 could be therapeutically targeted in
lung cancers in which its expression is high.