CYCS and cancer: Moreover, the cytotoxicity of the chloroform extract might have resulted from the activity of D-limonene, which has been demonstrated to induce cancer cell death by increasing the expression of pro-apoptotic proteins (e.g., Bax), inhibiting the Ras/Raf/ERK1/2 and PI3K/Akt signaling pathways, arresting the cell cycle, and enhancing the levels of cytochrome C [22].