Response to radiotherapy of human uterine cervix carcinoma is not correlated with rearrangements of the Ha-ras-1 and/or c-myc genes

c-Myc protein expression is not an independent prognostic predictor in cervical squamous cell carcinoma

The c-myc protein is known to regulate the cell cycle, and its down-regulation can lead to cell death by apoptosis. The role of c-myc protein as an independent prognostic determinant in cervical cancer is controversial. In the present study, a cohort of 220 Brazilian women (mean age 53.4 years) with FIGO stage I, II and III (21, 28 and 51%, respectively) cervical squamous cell carcinomas was analyzed for c-myc protein expression using immunohistochemistry. The disease-free survival and relapse-rate were analyzed using univariate (Kaplan-Meier) survival analysis for 116 women who completed the standard FIGO treatment and were followed up for 5 years. Positive c-myc staining was detected in 40% of carcinomas, 29% being grade 1, 9% grade 2, and 2% grade 3. The distribution of positive c-myc according to FIGO stage was 19% (17 women) in stage I, 33% (29) in stage II, and 48% (43) in stage III of disease. During the 60-month follow-up, disease-free survival in univariate (Kaplan-Meier) survival analysis (116 women) was lower for women with c-myc-positive tumors, i.e., 60.5, 47.5 and 36.6% at 12, 36, and 60 months, respectively (not significant). The present data suggest that immunohistochemical demonstration of c-myc does not possess any prognostic value independent of FIGO stage, and as such is unlikely to be a useful prognostic marker in cervical squamous cell carcinoma.

The farnesyl transferase inhibitor RPR-130401 does not alter radiation susceptibility in human tumor cells with a K-Ras mutation in spite of large changes in ploidy and lamin B distribution

BACKGROUND

Growth inhibition by RPR-130401, a non-peptidomimetic farnesyltransferase inhibitor, was investigated without or with combined exposure to ionizing radiation in three human tumor cell lines (HCT-116, MiAPaCa-2 and A-549) bearing a point mutation in the K-Ras gene.

RESULTS

RPR-130401 inhibited cell growth with an IC50 of 50 nM (HCT-116), 120 nM (MiAPaCa-2) and 710 nM (A-549), with a poor incidence of apoptosis. The drug brought about G1 and S phase depletion together with arrest of cells in G2 phase and induced a significant accumulation of hyperploid cells showing active S phase DNA synthesis, with HCT-116 and A-549 cells being the most and least responsive, respectively. The drug also produced dramatic changes of the nuclear lamin B pattern, without lamin B cleavage and perturbation of the actin cytoskeleton. On the other hand, RPR-130401 elicited strictly additive interaction in combined treatment with ionizing radiation with regard to cell kill, altered cell cycle progression and induced hyperploidy.

CONCLUSIONS

The data suggest that disruption of orderly progression through mitosis and cytokinesis, is a major outcome of drug action and that this effect proceeds from inhibition of lamin B farnesylation. It is anticipated from the strict additivity of RPR-130401 and radiation that neither induced radiation resistance nor acute or late complications of radiotherapy, should occur in combined treatment with RPR-130401.

Tumor radiosensitivity and apoptosis

With approximately 50% of all cancer patients receiving radiation therapy at some point in their treatment, increasing the sensitivity of tumor cells to the lethal effects of irradiation has the potential to significantly improve the rate of recovery from many malignancies. The major biological determinant of radiotherapy failure is tumor radioresistance. It is well known that tumors from the same histological group and stage of development are extremely heterogeneous in their sensitivity to radiotherapy. There are many factors which could affect tumor radiosensitivity. One cellular mechanism common to various therapeutic regiments, including radiation, is killing tumor cells via apoptosis. However, this killing is not always efficient. In this review the link between tumor sensitivity to radiation treatment and the capacity of tumor cells to be killed by apoptotic mechanisms will be discussed.

Uterine cervical dysplasia and cancer: identification of c-myc status by quantitative polymerase chain reaction

The c-myc oncogene status was determined in patients with nondysplasia (ND; 9 patients), low-grade squamous intraepithelial lesion (LGSIL; 12 patients), high-grade squamous intraepithelial lesion (HGSIL; 21 patients) and invasive squamous cell carcinoma (ISCC; 20 patients) of uterine cervix using fluorescent quantitative polymerase chain reaction (PCR). In the same paraffin-embedded specimens, other potential risk factors were also screened: human papillomavirus (HPV) infection, Ha-ras codon 12 mutation, DNA aneuploidy. Gene amplification, identified as c-myc copy numbers greater than the mean value +2 SD of patients with ND, was seen in 44% patients with LGSIL, 76% patients with HGSIL, and 67% patients with ISCC. These data indicate that c-myc amplification is one of the critical early events in the progression of uterine cervical lesions. HPV infection of various subtypes was identified in 0% patients with ND, 55% patients with LGSIL, 95% patients with HGSIL, and 84% patients with ISCC. No codon 12 mutation of the Ha-ras gene was found in this series. Aneuploid DNA pattern was seen in 0% patients with ND, 58% patients with LGSIL, 90% patients with HGSIL, and 80% patients with ISCC. There was a significant correlation between HPV infection and DNA aneuploidy. However, no relationship was seen between c-myc status and other factors in this series. Patients with HGSIL and ISCC almost always (95%) had multiple risk factors, whereas more than half of the patients with LGSIL had no or only one risk factor (P = 0.0001).