Evaluating the efficacy of HTL001, a cell penetrating peptide that targets the HOX/PBX interaction in ovarian cancer.

Abstract

HOX genes are a class of homeobox transcription factors that drive embryogenesis and generally are expressed during development and silent in the adulthood. Proliferation, invasion and metastasis have been related to an overexpression of HOX genes in various forms of carcinoma, including prostate, colorectal, melanoma, breast and ovarian. HOX genes appear to be a valid target for targeted therapies given their selective expression in malignant tissue. HXR9 is a cell penetrating peptide capable of disrupting the interaction between HOX genes and their co-factor PBX to prevent the activation of downstream HOX target genes (oncogenes?) and to induce selective apoptosis in cancer cells, in a molecular pathway that still need to be elucidated. HTL001 is a new version of HXR9 with a change in few aminoacids in the original sequence to enhance peptide synthesis, cell entry and efficacy of cell killing. HTL001 was tested on ovarian cancer cell lines and primary cultures. Its cytotoxicity was compared to HXR9 and it was proved that the mode of death was still apoptosis. The demonstrated drug efficacy in a wide range of carcinoma cell lines led us to test HTL001 in a new experimental platform, the precision cut tissue slice model that uses tissue obtained after surgery and therefore can resemble responses closer to a clinical setting. The 3D model was first optimised for viability and later tissue signs of apoptosis/necrosis after exposure with cisplatin and HTL001 evaluated. The limited cytotoxicy of HTL001 on ovarian cancer precision cut slices prompted us to investigate another strategy for drug delivery and the approach to insert multiple copies of HTL001 into a viral vector for long-term expression appeared to be a valid alternative that was evaluated in preliminary experiments transfecting ovarian cancer cell lines with different expression cassettes. Finally, the molecular pathway of HTL001 leading to apoptosis was investigated to identify potential biomarkers of response and targets for combinational therapy.