Apolipoprotein(a) Kringles for Gene Therapy of Colon Cancer

Lipoprotein(a) is a proatherogenic, prothrombotic lipoprotein that comprises apolipoprotein(a) (apo(a)) tethered to apolipoprotein B-100, which surrounds a low-density lipoprotein (LDL) moiety. Despite its molecular similarity to plasminogen, apo(a) plays distinct physiological and pathological roles both in vitro and in vivo. In this study, we examined possible target molecules and the therapeutic potential of gene therapy using a recombinant adeno-associated virus (AAV) carrying the LK8 and LK68 (LKs) genes, which encode the cryptic kringle fragment of apo(a) (rAAV-LK), for the treatment of colon carcinoma. The results showed that AAV-produced LKs inhibited the migration of HUVECs induced by different angiogenic factors in a dose-dependent manner, and the potency was >1,000-fold than that of recombinant LK8 and LK68 proteins. A single intramuscular injection of rAAV-LKs (1 × 10 ⁹ infectious particles (IP)/mouse) significantly inhibited the growth of subcutaneously transplanted LS174T tumors and reduced the number of tumor nodules in metastasized livers. Immunohistochemical analysis showed that AAVproduced LKs inhibited microvessel formation within the tumor mass, thereby inducing apoptosis in the tumor periphery, leading to the suppression of both tumor growth and metastasis. Taken together, these results suggest that AAV-produced LKs are multi-potent angiogenesis inhibitors that suppress the growth and metastasis of colon carcinoma.