CAPN1 and triple-negative breast carcinoma: To study calpain-dependent metastasis, using the lentiCRISPRv2 CRISPR-Cas9 knockout (KO) system [29], we tested the effect of individual CAPN1 or CAPN2 KOs in the human triple-negative breast cancer cell line MDA-MB-231, or disruption of both calpain-1/2 through KO of CAPNS1, encoding the common regulatory subunit which renders both catalytic subunits inactive and unstable [7].