Calponin-1

Calponin-1 (CALP) is a protein that binds to actin and tropomyosin in smooth muscle cells. It can inhibit smooth muscle contraction by reducing myosin ATPase activity in thick filaments and decreasing actin movement speed in thin filaments. In clinical practice, CALP can be used for the diagnosis of tumors derived from smooth muscle cells and myofibroblasts. Especially in endometrium, its positive rate in bizarre or cellular leiomyoma is significantly higher than that in stromal sarcoma, which makes it become an assisting differential biomarker. In addition, CALP can be expressed in lung cancer, gastric cancer, breast cancer, bladder cancer, and other malignant diseases, and it is closely related to tumor metastasis and drug resistance. This is because the abnormally increased CALP can induce epithelial-mesenchymal transition (EMT), activate cell migration signaling pathways and up-regulate tumor-associated fibroblasts. However, some scholars pointed out that CALP negative cervical cancer patients have worse prognosis, speculated that its deficiency may disrupt cellular structural stability and promote tumor angiogenesis.