Abstract: The invention provides methods for selective targeting of live cells, which have undergone or are undergoing radiation or chemotherapy, at a site of interest with a cell-penetrating polypeptide. In one embodiment of the invention, the method comprises contacting the live cells with a cell-penetrating polypeptide comprising cell-penetrating determinants so that the cell-penetrating polypeptide binds extracellular DNA near or around the live cells so as to form a complex or association therewith such that the complex or associated polypeptide-DNA so bound bind the live cells and penetrates the live cells thereby selectively targeting live cells at a site of interest with a cell-penetrating polypeptide.

Abstract: The invention provides a method for inhibiting an intracellular target in a cell with a bispecific antibody comprising contacting the cell with a bispecific antibody having a first Fv fragment with a cell-penetrating determinant and a second Fv fragment with an intracellular target-binding determinant under suitable conditions so that the first Fv fragment causes the bispecific antibody to enter the cell and the second Fv fragment binds the intracellular target in the cell and thereby inhibiting the intracellular target.

Abstract: The invention provides for a fusion protein comprising a 3E10 Fv joined to a Hsp-70, Hsp-27, Hsp-90 or GRP-78or portion thereof, and optionally, the 3E10 Fv comprising an amino acid sequence AGIH at its amino terminus.

Abstract: Antibodies that penetrate cell nuclei and inhibit DNA repair or interfere with DNA metabolism are provided for treatment of cancer (both directly and by sensitizing cancer cells to DNA-damaging treatments) or inhibiting or preventing viral infection, proliferation or metabolism. The method involves treating cells with a composition containing cell-penetrating anti-DNA antibodies or derivatives thereof, alone or in combination with treatment that induces DNA damage such as DNA-damaging chemotherapy or radiation. The impact of the cell-penetrating anti-DNA antibodies or derivatives thereof is potentiated in cancer cells that are deficient in DNA repair, and the cell-penetrating anti-DNA antibodies or derivatives thereof are synthetically lethal to cancer cells with DNA repair deficiencies.

Abstract: The invention provides a method for inhibiting an intracellular target in a cell with a bispecific antibody comprising contacting the cell with a bispecific antibody having a first Fv fragment with a cell-penetrating determinant and a second Fv fragment with an intracellular target-binding determinant under suitable conditions so that the first Fv fragment causes the bispecific antibody to enter the cell and the second Fv fragment binds the intracellular target in the cell and thereby inhibiting the intracellular target.

Abstract: The invention provides for a fusion protein comprising a 3E10 Fv joined to a Hsp-70, Hsp-27, Hsp-90 or GRP-78 or portion thereof, and optionally, the 3E10 Fv comprising an amino acid sequence AGIH at its amino terminus.