The present invention provides a means of selectively killing epithelial cell carcinomas by administering a CXCR4-specific sequence of the Gp120 protein or Nef proteins or the proteins themselves (the modulators) such as that found in strains HIV-1, HIV-2, SIV, or FIV CXCR4-specific Gp 120 sequences or Nef proteins or sequences may be delivered to the mucosa or systemically. The mucosal means of application include oral, intranasal, ocular, intravaginal, rectal, and/or intraurethral administration in liquid or particulate form.