in terms of mouse cell lines, 4t1 cells are agressively metastatic from the orthotopic site in balb/c and nude mice. 67NR and 66cl4 cell lines are derived from the same tumor as the 4t1 cells, they form tumors in both strains but are less metastatic. For human cell lines you can use mdamb23, mdamb468, mdamb436, sum1315, mcf7 cells. All are tumorigenic, but poorly metastatic from the orthotopic site. People (joan massugue lab) have generated variants of the mdamb231 cells in vivo that are metastatic from the orthotopic site.

We work with orthotopic models of colorectal cancer and to my experience, HCT116 and HT29 cells are two of the best human colorectal cancer cell lines that you can use in nude or SCID mice to induce orthotopic model.

I agree with both comments above. Mousecell line 4T1 are good, I have worked with them and got excellent results. Breast cell lines are MCF7, but problems arose with having to implant E2 pellets and therefore causing Haggis Bladder. MDA231 and BT20 are good cell lines to use. Colon, again, I have just finished an experiment with HCT116 and they were very agressive, another is HT29.

And, If you're interested in metastasis, this group showed that MDA-MB-436, MDA-MB-231, and MCF-7 will metastasize from the orthotopic site when used in nod-scid-gamma mice

The most metastasis cell lines of breast cancer that i have tested is mda mb 231

I agree with both April Rose and Azadeh Arabzadeh. However, a word of caution: It is not possible to import NSG mice into India. As far as I know, Jackson's is the only supplier and they don't supply in India