The present invention provides, inter alia, methods for treating or ameliorating the effects of a disease, such as cancer, in a subject. The methods include: administering to a subject in need thereof (a) a therapeutically effective amount of an agent selected from an anti-metabolite agent or analog thereof and combinations thereof; and (b) a therapeutically effective amount of a monoclonal antibody or antigen binding fragment thereof, wherein the monoclonal antibody contains: (i) a heavy chain variable region (VH), which includes an amino acid sequence selected from SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, and SEQ ID NO:7; and (ii) a light chain variable region (VL), which includes an amino acid sequence selected from SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, and SEQ ID NO:8. Compositions, including pharmaceutical compositions, and kits for treating diseases, such as cancer, are also provided herein.