HDM-2-Targeting Peptide PNC-27 Kills Cervical Cancer Cells but not Normal Cervical Cells

The peptide PNC-27 has been found to kill many different endodermal solid tissue and hematopoietic cancer cells but has no effect on normal cells. The mechanism involves binding to the HDM-2 protein, which is expressed in the membranes of cancer cells but not in normal (untransformed) cells. Our objectives in the current study are to determine 1) if PNC-27 is lethal to squamous cervical epithelial cancer cells but not to untransformed squamous cervical cells; 2) if membrane-bound HDM-2 is expressed uniquely in cervical cancer cells; and 3) whether HDM-2 is stable for detection in different types of preservative solutions.

We determined dose response curves for incubation of PNC-27 with the human squamous cervical cancer cell line HTB-35 (also called SiHa cells) and with the untransformed human squamous cervical cell line, PCS-480. Cell viability was determined using the MTT and LDH release assays. Finally, slot blots and flow cytometry were used to determine membrane expression of HDM-2 using a polyclonal anti-HDM-2 antibody.

We found that PNC-27 is cytotoxic even at low doses (IC₅₀=12.4 μM) to the human HTB-35 cervical cancer squamous epithelial cell line but not to a counterpart normal human PCS-480 cell line. We found that HTB-35 cells express high levels of HDM-2 proteins in their membranes both in cell culture and in alcoholic preservative solutions but that the normal PCS-480 cells do not. Consistent with previous results, the data suggest that cervical cancer cells express HDM-2 in their membranes and that this is the target for PNC-27.

PNC-27 kills cervical squamous cancer but not normal cervical cells due to the unique expression of HDM-2 in the cervical squamous cell membranes. Thus, PNC-27 may be an effective drug against this cancer. Our results further suggest that the expression of membrane-bound HDM-2 on cervical cancer cells is stable both in cell culture media and in alcoholic preservative fluid.