Prediction of radiosensitivity of oral cancers by serial cytological assay of nuclear changes

Evaluation of Various Nuclear Cytological Changes in Normal Buccal Mucosa and Peritumoural Area in Patients with Oral Squamous Cell Carcinoma Receiving Concomitant Chemoradiotherapy

Objectives. To evaluate the role of serial cytological assay in calculating the nuclear response of contralateral normal buccal mucosa and peritumoural area of squamous cell carcinoma of oral cavity in patients receiving fractionated radiotherapy (RT) and chemotherapy. Materials and Methods. This prospective, nonrandomized study was comprised of 76 histologically confirmed cases of oral squamous cell carcinoma on cyclical chemoradiation treatment. Chemoradiosensitivity was evaluated using serial scrape smears taken before and after immediate exposure to CCRT, at 17th day of CCRT (mid of treatment), and at the end of treatment. The nuclear changes, such as multinucleation, micronucleation, karyorrhexis, karyolysis, nuclear budding, prominent nucleoli, and binucleation occurring in both irradiated cancer cells and contralateral normal buccal mucosa, had a statistically significant dose related increase with concomitant chemoradiotherapy (p < 0.05). Conclusion. We recommend regular use of serial cytological assay during CCRT as it may prove to be a valuable tool for assessment of chemoradiosensitivity and persistence of tumour/dysplastic cells after radiotherapy.

Genotoxic anti-cancer agents and their relationship to DNA damage, mitosis, and checkpoint adaptation in proliferating cancer cells

When a human cell detects damaged DNA, it initiates the DNA damage response (DDR) that permits it to repair the damage and avoid transmitting it to daughter cells. Despite this response, changes to the genome occur and some cells, such as proliferating cancer cells, are prone to genome instability. The cellular processes that lead to genomic changes after a genotoxic event are not well understood. Our research focuses on the relationship between genotoxic cancer drugs and checkpoint adaptation, which is the process of mitosis with damaged DNA. We examine the types of DNA damage induced by widely used cancer drugs and describe their effects upon proliferating cancer cells. There is evidence that cell death caused by genotoxic cancer drugs in some cases includes exiting a DNA damage cell cycle arrest and entry into mitosis. Furthermore, some cells are able to survive this process at a time when the genome is most susceptible to change or rearrangement. Checkpoint adaptation is poorly characterised in human cells; we predict that increasing our understanding of this pathway may help to understand genomic instability in cancer cells and provide insight into methods to improve the efficacy of current cancer therapies.

Radiation-induced cell death mechanisms

The main goal when treating malignancies with radiation therapy is to deprive tumor cells of their reproductive potential. One approach to achieve this is by inducing tumor cell apoptosis. Accumulating evidences suggest that induction of apoptosis alone is insufficient to account for the therapeutic effect of radiotherapy. It has become obvious in the last few years that inhibition of the proliferative capacity of malignant cells following irradiation, especially with solid tumors, can occur via alternative cell death modalities or permanent cell cycle arrests, i.e., senescence. In this review, apoptosis and mitotic catastrophe, the two major cell deaths induced by radiation, are described and dissected in terms of activating mechanisms. Furthermore, treatment-induced senescence and its relevance for the outcome of radiotherapy of cancer will be discussed. The importance of p53 for the induction and execution of these different types of cell deaths is highlighted. The efficiency of radiotherapy and radioimmunotherapy has much to gain by understanding the cell death mechanisms that are induced in tumor cells following irradiation. Strategies to use specific inhibitors that will manipulate key molecules in these pathways in combination with radiation might potentiate therapy and enhance tumor cell kill.

Radiation therapy induced micronuclei in cervical cancer—does it have a predictive value for local disease control?

OBJECTIVE

To evaluate the predictive value of serial changes in micronuclei induction during external radiotherapy (EXRT) in cervical cancer with respect to local response at the end of EXRT and local disease free survival (LDFS).

METHODS

Twenty-five patients of squamous cell cancer of the cervix were treated by 50 Gy of EXRT delivered over 5 weeks followed by intracavitary brachytherapy. Serial cytological smears were taken from cervical growth at weekly intervals during the course of EXRT and stained by Giemsa and May-Grunwald's stain. Micronuclei induction were scored as (a) number of cells expressing micronuclei (MN), and (b) total number of micronuclei (TMN) in 1000 tumor cells from each of the serial smears.

RESULTS

A significant rise in micronuclei count was seen for both MN and TMN from pretreatment (week 0) to successive weeks of EXRT. For those having a near total tumor regression by end of EXRT, a significant rise in micronuclei was evident even at the end of first week of EXRT (MN: P = 0.05, TMN: P = 0.04). A superior LDFS was observed in patients showing greater than 50% increment in MN value in the first week (median survival for <50% vs. > or =50% rise: 5 months vs. not reached, P = 0.21), while it reached significance for a similar rise of TMN (median survival <50% vs. > or =50% rise: 5 months vs. not reached, P = 0.04).

CONCLUSIONS

The significant rise of micronuclei at the end of first week of EXRT in cervical cancers as observed from serial cytological smears could predict for a better local response and LDFS.

Radiation-induced senescence-like terminal growth arrest in thyroid cells

Premature senescence may play an important role as an acute, drug-, or ionizing radiation (IR)-inducible growth arrest program along with interphase apoptosis and mitotic catastrophe. The aim of the study was to evaluate whether IR can induce senescence-like phenotype (SLP) associated with terminal growth arrest in the thyroid cells, and if so, to evaluate impact of terminal growth arrest associated with SLP in intrinsic radiosensitivity of various thyroid carcinomas. The induction of SLP in thyroid cells were identified by: (1) senescence associated beta-galactosidase (SA-beta-Gal) staining method, (2) dual-flow cytometric analysis of cell proliferation and side light scatter using vital staining with PKH-2 fluorescent dye, (3) double labeling for 5-bromodeoxyuridine and SA- beta-Gal, (4) Staining for SA-beta-Gal with consequent antithyroglobulin immunohistochemistry. IR induced SLP associated with terminal growth arrest in four thyroid cancer cells lines and in primary thyrocytes in time- and dose-dependent manner. Analysis of relationship between induction of SLP and radiosensitivity revealed a trend in which more radioresistant cell lines strongly tended to show lower specific SLP yields (r = -0.93, p = 0.068). We find out that SA-beta-Gal staining is detectable in irradiated ARO xenotransplants, but not in control tumors. We, therefore, conclude that induction of SLP with terminal growth arrest contribute to the elimination of clonogenic populations after IR.

Genetic damage in exfoliated cells from oral mucosa of individuals exposed to X-rays during panoramic dental radiographies

The genotoxic effects of X-ray emitted during dental panoramic radiography were evaluated in exfoliated cells from oral epithelium through a differentiated protocol of the micronucleus test. Thirty-one healthy individuals agreed to participate in this study and were submitted to this procedure for diagnosis purpose after being requested by the dentist. All of them answered a questionnaire before the examination. Cells were obtained from both sides of the cheek by gentle scrapping with a cervical brush, immediately before the exposure and after 10 days. Cytological preparations were stained according to Feulgen-Rossenbeck reaction and analyzed under light and laser scanning confocal microscopies. Micronuclei, nuclear projections (buds and broken eggs) and degenerative nuclear alterations (condensed chromatin, karyolysis and karyorrhexis) were scored. The frequencies of micronuclei, karyolysis and pycnosis were similar before and after exposure (P > 0.90), whereas the condensation of the chromatin and the karyorrhexis increased significantly after exposure (P < 0.0001). In contrast, both bud and broken egg frequencies were significantly higher before the examination (P < 0.005), suggesting that these structures are associated to the normal epithelium differentiation. The results suggest that the X-ray exposure during panoramic dental radiography induces a cytotoxic effect by increasing apoptosis. We also believe that the score of other nuclear alterations in addition to the micronucleus improves the sensitivity of genotoxic effects detection.

Radiation-induced changes in oral carcinoma cells - a multiparametric evaluation

The aim of this study was to see whether serial cytological evaluation of various cellular abnormalities in tumours from patients receiving fractionated radiotherapy can predict radio-response in oral carcinoma. Cytological assessment was carried out in scrape smears collected prior to and during the course of radiotherapy in 68 patients with squamous cell carcinoma of the oral cavity planned for radical radiotherapy with accelerated fraction schedule. Smears were evaluated for a set of 15 radiation-induced cellular abnormalities. The relationship between the cellular alterations and the cumulative radiation dose was analysed by Kruskal-Wallis one-way anova. The results showed that among the various quantifiable changes that occur in irradiated cancer cells, karyolysis, karyorrhexis, pyknosis, cytolysis, multinucleation, micronucleation and nuclear budding show significant increase depending on the dose of radiation. The radio-resistant group of patients exhibited a lesser degree of change compared with the radio-sensitive group. This suggests that radio-resistance may be due to the defective induction of cell damage and that these cytological features may have potential use as predictive markers of radio-sensitivity in oral carcinoma.

Reasons to reconsider the significance of apoptosis for cancer therapy

In recent years, the significance of apoptosis as a process in cell loss from normal tissue and tumours has been critically reviewed. In addition, the general lack of a correlation between radiation or drug-induced apoptosis and cell survival responses (using the clonogenic assay) in tumour cells has been demonstrated. Several different reasons have been discussed by other authors. It is the purpose of this review to argue that there are many different forms of cell death (terminal differentiation, micronucleation, mitotic catastrophe or multinucleation) that, like apoptosis, are regulated by the cell. In this context, apoptosis was the first cell death mechanism associated with active involvement of the cell (signal transduction). Furthermore, a large variety of different in vitro and a few in vivo models published so far show that the form of cell death can shift from, for example, mitotic catastrophe to apoptosis. The shift appears to be a general principle and depends on the cell model examined, the stressor type and the stressor intensity. These considerations help to explain the absence of a simple link between apoptosis and clonogenicity and suggest how to overcome that limitation, which has implications for the significance of apoptosis where the diagnosis and prognosis of cancer are concerned.

p16 Gene transfer increases cell killing with abnormal nucleation after ionising radiation in glioma cells

It is well established that cells synchronised at the G1–S phase are highly radiosensitive. In this study, p16-null human glioma cell lines were induced into G1 cell cycle arrest by adenovirus-mediated p16 gene transfer, and examined for radiation-induced cell killing. Clonogenic analysis and trypan blue extraction test showed that the p16 gene transfer enhanced radiation-induced cell killing in p16-null glioma cell lines. TUNEL assays and pulse-field gel electrophoresis confirmed that the radiation-induced cell killing of p16-transfected cells could be caused by a nonapoptotic mechanism. Gimsa staining demonstrated that irradiation alone or Ax-mock infection plus irradiation results in a slight increase in the frequency of cells with abnormal nucleus, compared to unirradiated uninfected or Ax-mock infected cells. However, Ax-hp16 or Ax-hp21 infection alone modestly increased the frequency of cells with abnormal nucleus (especially bi- and multinucleation), and 4-Gy irradiation of Ax-hp16 or Ax-hp21 infected cells substantially enhanced this frequency. These results suggest that there exists some unknown interaction between radiation and p16 in cytoplasm/membranes, which decreases cytokinesis and promotes abnormal nucleation. Thus, p16 expression prevented radiation-induced apoptosis by promoting abnormal nucleation, thereby leading to another mode of cell death.

Cumulative interfraction interval analysis of time and fraction size in radiotherapy

AIMS

Overall treatment time (OTT) and fraction size influence treatment results with radiotherapy; yet, being inversely related, it is difficult to distinguish their effect independently of each other. This paper proposes a new approach for analysing the interrelationship of time and fraction size in terms of cumulative interfraction intervals (CIFI) (i.e. intervals between non-successive fractions of radiotherapy).

MATERIALS AND METHODS

We analysed the influence of CIFI1-6, CIFI1-11 and OTTon tumour control by Kaplan-Meier calculation of the primary relapse-free survival (PRFS) and Mann Whitney 'U' test in 242 patients with epidermoid cancer of the buccal mucosa-gingiva-palate region treated by either 2.4 Gy/fraction (60 Gy/5 weeks) or 3.5 Gy/fraction (52.5 Gy/3 weeks).

RESULTS

The results showed that (1) prolongation of CIFI1-11 significantly decreased tumour control in the 2.4 Gy but not 3.5 Gy schedule: (2) 3.5 Gy schedule was superior to 2.4 Gy schedule, particularly when CIFI1-11 was prolonged (5-year PRFS 80.3% vs 30.9%); and (3) OTT did not influence either schedule.

CONCLUSIONS

Prolonging interfraction intervals (by treatment interruptions, weekend gaps, etc.) in the first 2 weeks (when accelerated repopulation attempts are maximal) affects treatment results with low fraction sizes but not high fraction sizes; OTT probably vicariously reflects the effect of prolonging the intervening CIFI.

Cumulative interfraction interval analysis of influence of time and interruptions on radiotherapy results in oral cancers

PURPOSE

To present a new approach to analyze the influence of time and interruptions in fractionated radiotherapy, in terms of cumulative interfraction intervals (CIFIs), that is, the interval between nonsuccessive fractions of radiotherapy.

METHODS AND MATERIALS

The subjects were 142 patients with epidermoid cancer of the buccal mucosa-gingiva-palate region treated by 60 Gy in 25 fractions during 5 weeks. The influence of CIFI between the first and sixth, eleventh, sixteenth, and twenty-first fractions (CIFI(1-6), CIFI(1-11), CIFI(1-16), and CIFI(1-21), respectively), as well as overall treatment time on local control, was analyzed by Kaplan-Meier calculation of the primary relapse-free survival and Mann-Whitney U testing of the difference in various CIFIs between the tumors that recurred (recurred group) and those that did not (controlled group).

RESULTS

Only CIFI(1-11) influenced local control significantly, with the 5-year primary relapse-free survival rate being 67.9%, 48.4%, and 32.6% in those with CIFI(1-11) of <14, 14, and >14 days (p = 0.0181). The median CIFI(1-11) in the controlled group was significantly lower than that in the recurred group (14 days vs. 15 days; p = 0.0037).

CONCLUSION

Interruptions during the first 11 fractions, including planned weekend gaps, decrease the effect of radiotherapy, possibly because of successful tumor cell repopulation during the protracted interfraction intervals. The analysis of time in terms of CIFI rather than overall treatment time appears to be a promising area for research.

If not apoptosis, then what? Treatment-induced senescence and mitotic catastrophe in tumor cells

Inhibition of the program of apoptosis has been reported to have little or no effect on clonogenic survival after treatment with drugs or radiation in several tumor cell lines. A decrease in apoptosis is compensated in such cell lines by an increase in the fractions of cells that undergo permanent growth arrest with phenotypic features of cell senescence, or die through the process of mitotic catastrophe. Most of the tested tumor cell lines have retained the capacity of normal cells to undergo accelerated senescence after treatment with DNA-interactive drugs, ionizing radiation, or cytostatic agents. p53 and p21(Waf1/Cip1/Sdi1) act as positive regulators of treatment-induced senescence, but they are not required for this response in tumor cells. The senescent phenotype distinguishes tumor cells that survived drug exposure but lost the ability to form colonies from those that recover and proliferate after treatment. Although senescent cells do not proliferate, they are metabolically active and may produce secreted proteins with potential tumor-promoting activities. The expression of such proteins is mediated at least in part by the induction of p21(Waf1/Cip1/Sdi1). The other anti-proliferative response of tumor cells is mitotic catastrophe, a form of cell death that results from abnormal mitosis and leads to the formation of interphase cells with multiple micronuclei. Mitotic catastrophe is induced by different classes of cytotoxic agents, but the pathways of abnormal mitosis differ depending on the nature of the inducer and the status of cell-cycle checkpoints. Mitotic catastrophe can also develop as a consequence of aberrant reentry of tumor cells into cell cycle after prolonged growth arrest. Elucidation of the factors that regulate different aspects of treatment-induced senescence and mitotic catastrophe should assist in improving the efficacy and decreasing side effects of cancer therapy.

Relation of erythrocyte and iron indices to oral cancer growth

BACKGROUND AND PURPOSE

Anaemia is known to influence prognosis of head and neck cancer patients, but how anaemia and tumour growth influences each other is not clear. The present study investigates the relation of erythrocyte and iron indices of oral cancer patients to primary tumour size (Tsize), invasiveness and lymph node involvement.

MATERIALS AND METHODS

The haemoglobin (Hb), erythrocyte count (RBC), packed cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), Serum iron (SFe), transferrin iron-binding capacity (TIBC) and transferrin saturation (%Fe) were evaluated in 217 untreated patients with epidermoid cancer of the bucco-gingivo-palatine area. The association of erythrocyte and iron indices with sex, tumour size groups, invasion of adjacent structures and lymph node involvement, as well as the relation of SFe to Hb were analyzed.

RESULTS

Most of the patients were anaemic in terms of Hb (63%), RBC (43%) and PCV (48.4%) but almost all had normal or higher MCH (97.3%) and MCV (93.3%) though MCHC was less than normal in 70.7%. Normal or higher SFe was seen in nearly 70% and TIBC in 45% of patients. Hb, RBC and PCV were significantly lower in women, but there was no difference between men and women in the case of MCV, MCH and MCHC. Primary tumour size showed negative association with Hb, RBC and PCV but positive association with MCH (< 2 cm: 29.7 pg; 2-4 cm: 31.4 pg; > 4 cm: 31. 7 pg; P = 0.04) and MCHC (< 2 cm: 29.9; 2-4 cm: 31.5; > 4 cm: 32.1; P = 0.006). MCV, SFe, TIBC and %Fe did not show any relation to primary tumour size. None of the indices had any relation to invasion of adjacent structures or lymph node involvement. MCH, MCHC and MCV were not different in men and women but women had significantly lower Hb, RBC and PCV. The SFe showed poor correlation with Hb.

CONCLUSIONS

The negative association of Hb, RBC and PCV with tumour size is most likely due to chronic RBC destruction, probably tumour induced, with the products of haemolysis such as polyamines, glutathione, iron, etc., promoting tumour growth, and the positive association with MCH and MCHC reflects compensatory regeneration attempts by bone marrow. Lack of relation between the iron indices and tumour parameters and the poor correlation between SFe and Hb is probably due to utilization of iron by both bone marrow and tumours. Lack of difference in MCH and MCHC between men and women obviates the need of using separate cut-off values for the two sexes, unlike Hb, RBC and PCV. The study suggests that anaemia in oral cancer patients represents a tumour-host interaction and that evaluation of all erythrocyte indices should be part of research on cancer related anaemia.