This invention provides pharmaceutical uses for 2-methylene-19-nor-20-1\u03b1,25-dihydroxyvitamin D3. Illustrative compositions comprise one or more colon tumor polypeptides, immunogenic portions thereof, polynucleotides that encode such polypeptides, antigen presenting cell that expresses such polypeptides, and T cells that are specific for cells expressing such polypeptides. The derivative has high affinity and good stability in animal’s body. Also provided are methods for inhibiting metastasis of breast carcinomas and methods for identifying HMW-MAA+ breast cancer stem cells. Each of the first and second ground planes are in mechanical and electrical contact with one another when the plug is mated to the receptacle. Each of the support brackets is movably mounted on the track and provided with a slide member, a fastening member, a limit member and a stop member.