Proliferative characteristics of head and neck tumors. In vivo evaluation by bromodeoxyuridine incorporation and flow cytometry

Where Do We Look for Markers of Radiotherapy Fraction Size Sensitivity?

The response of human normal tissues to radiotherapy fraction size is often described in terms of cellular recovery, but the causal links between cellular and tissue responses to ionising radiation are not necessarily straightforward. This article reviews the evidence for a cellular basis to clinical fractionation sensitivity in normal tissues and discusses the significance of a long-established inverse association between fractionation sensitivity and proliferative indices. Molecular mechanisms of fractionation sensitivity involving DNA damage repair and cell cycle control are proposed that will probably require modification before being applicable to human cancer. The article concludes by discussing the kind of correlative research needed to test for and validate predictive biomarkers of tumour fractionation sensitivity.

DNA ploidy, proliferative capacity and intratumoral heterogeneity in primary and recurrent head and neck squamous cell carcinomas (HNSCC) – Potential implications for clinical management and treatment decisions

Despite new diagnostic and therapeutic strategies (combined radiochemotherapy, EGFR antibody Cetuximab), the prognosis of head and neck squamous cell carcinoma (HNSCC) is still poor and more information regarding prognosis is essential to establish earlier and better treatment options. To elucidate the role of DNA ploidy and cellular proliferation, resected tumors of 48 patients with primary or recurrent HNSCC were analyzed by flow cytometry and in vitro-5-bromodeoxyuridine incorporation (BrdU). The results were compared with histopathological findings such as tumor size, lymph node involvement and tumor differentiation. To assess the influence of intratumoral heterogeneity of these biological parameters, multiple biopsies (>3) were analyzed by flow cytometry and BrdU-incorporation in 12 larger (>4 cm diameter) tumors. BrdU-labeling index (LI%) was significantly higher in aneuploid HNSCC and correlated significantly with poor histologic differentiation of the analyzed tumor tissues (P<0.001). Furthermore, a trend for higher LI% in nodal positive tumors was observed. Aneuploid HNSCC showed significantly more often tissue dedifferentiation (P=0.049) and in most cases an advanced tumor stage, especially in tumors with biclonal cell lines. Lymph node involvement was also seen more often in aneuploid and undifferentiated tumors. As in aneuploid tumors recurrent HNSCC showed in most cases a higher LI% and poor tissue differentiation, but as a result of the small collection of samples there was no correlation between aneuploidy and tumor recurrence. To proof the robustness of the acquired data and to estimate the influence of intratumoral heterogeneity to ploidy and LI% multiple biopsies were analyzed in larger tumors. Using a specific statistical algorithm a secure estimation of ploidy and LI% was possible by a single biopsy in these tumors. These findings indicate aneuploidy and proliferative activity as important findings for malignant progression in HNSCC. An estimation of these biological parameters may be useful for identification of patients with high risk for lymph node involvement or tumor recurrence and pre-treatment can be performed by a single biopsy. As a conclusion, these patients may benefit from more aggressive treatment.

Prognostic relevance of cell proliferation in head and neck tumors

Cell proliferative activity has been extensively investigated in head and neck tumors. Ki67/MIB-1 immunostaining, tritiated thymidine or bromodeoxyuridine labeling indices, DNA S-phase fraction, proliferating cell nuclear antigen expression, potential doubling time and analysis of the nucleolar organizer region associated proteins (AgNORs) have shown significant correlation with prognosis in 4806 cases of tumors of the oral cavity, salivary glands, pharynx and larynx. However, this was not observed in 2968 other reported cases. Discrepancies may depend on various factors: the heterogeneity of the series, which include tumors from various anatomic sites and patients treated with different therapy, and the lack of standardization of methods for assessing cell proliferation. Furthermore, none of the methods currently applied can by themselves define the actual proliferative activity, as it depends both on the proportion of cells committed to the cycle (growth fraction) and the speed of the cell cycle. Indeed, the actual proliferative activity of a tumor could well be measured by the equation [PA = Ki67 or MIB-1 scores x AgNORs], as we did in pharyngeal carcinoma. Provided that large and homogeneous series are evaluated by standardized methods, cell proliferative activity can still be regarded as an inexpensive and reliable prognostic factor in head and neck tumors.

Proliferative capacity in head and neck cancer

BACKGROUND

Shortening of overall treatment time (accelerated radiotherapy) appears to result in an increase of the efficacy of irradiation. In this study, we compared the proliferative capacity between tumors originating in different sites of the head and neck region. Tumors with a large proliferating capacity might, theoretically, benefit most from accelerated radiotherapy.

MATERIAL AND METHODS

BrdUrd was administered intravenously in patients with head and neck carcinomas. Tumor samples were analyzed with flow cytometry. T and N stages were assessed in accordance with the TNM classification system (UICC 1987).

RESULTS

No significant differences in proliferation parameters were observed with respect to site of origin of head and neck tumors. For T3/T4 tumors, DNA ploidy is an important tumor characteristic: G1- and S-phase fractions, labeling index, and tumor doubling time Tpot differences were statistically significant; the aneuploid tumors showed the largest proliferative potential.

CONCLUSIONS

(1) In general, no significant differences in proliferation parameters were observed with respect to site of origin. (2) Aneuploid head and neck tumors have a higher proliferative capacity than diploid ones, they might benefit most from accelerated irradiation.

Interrelationships of DNA-ploidy and cell proliferation markers with T-stage and N-stage in primary laryngeal tumors

PURPOSE

The purpose of this study was to evaluate the interrelationships of DNA-ploidy and cell proliferation markers with T-stage and N-stage in primary laryngeal tumors.

METHODS AND MATERIALS

DNA-index, S-phase fraction (SPF), 5-bromo-2'-deoxy-uridine (BrdUrd)-labeling index (LI), duration of S-phase (Ts), and potential doubling time (Tpot) were determined by flow cytometry. T-stage and N-stage were assessed in accordance with the TNM classification system (UICC 1987).

RESULTS

T1-2-, when compared with T3-4-stage tumors, had significantly higher LI values (independent from N-stage) resulting in lower Tpot values. No such relationship was found with respect to N-stage. N1-3 tumors, as opposed to NO tumors, appeared to be characterized by a significantly shorter Ts (and, hence, a shorter Tpot). Ts values appeared to vary considerably (range 1.9-6.2 h). For DNA-aneuploidy, as opposed to DNA-diploidy, a significantly higher geometric mean LI was noted. Locally advanced (T3-4) tumors, when compared with T1-2 tumors, were characterized by a significantly higher percentage of DNA-aneuploidy.

CONCLUSIONS

The reported lack of prognostic relevance of cell proliferation markers to predict radiation treatment efficacy may relate to a decreased proliferative capacity (LI, Tpot) in locally advanced (T3-4) tumors, as found in our series. In laryngeal tumors, the predictive value of cell proliferation markers (LI, Tpot) should, therefore, be evaluated after stratification for T-stage. The existence of higher LI values in DNA-aneuploidy tumors was confirmed in our series, stressing the need for distinction of DNA-diploid tumor cells from DNA-diploid normal cells. The prognostic potential of DNA-index was confirmed.