Expression de c-kit dans les carcinomes nasopharyngés nord africains, corrélations avec l'âge et LMP1

Changes in c-Kit expression levels during the course of radiation therapy for nasopharyngeal carcinoma

In the era of intensity-modulated radiotherapy, distant metastasis is currently the main cause of treatment failure for nasopharyngeal carcinoma (NPC). Additional therapeutic strategies are required to control the metastasis and improve survival. One strategy is targeted therapy, for example against c-Kit. In the current study, the frequency of c-Kit expression was determined immunohistochemically in 106 NPC patients. c-Kit expression changes during the course of radiation therapy were detected in 41 cases via weekly biopsy. Twelve cases (11.3%) had c-Kit expression scores of 3⁺ and 16 (15.1%) had scores of 2⁺. Thus, c-Kit overexpression (2⁺ or 3⁺) was observed in 28 (26.4%) patients. There were 35 (33.0%) and 43 (40.6%) patients with c-Kit expression scores of 1⁺ and 0, respectively. Furthermore, a trend of decreased c-Kit expression was observed after commencing radiotherapy according to the 41 NPC patients who were biopsied weekly. Therefore, c-Kit overexpression was identified to be common in NPC, and evaluating c-Kit as a therapeutic target for metastatic NPC via c-Kit overexpression subsequent to first line treatment may be of interest. To the best of our knowledge, the present study is the first to demonstrate a trend of decreased c-Kit expression during the course of radiotherapy.

[North African and Southeast Asian nasopharyngeal carcinomas: between the resemblance and the dissemblance]

Nasopharyngeal carcinoma (NPC) is an unusual head and neck cancer because of its unequal geographical distribution and its consistent association with the Epstein-Barr virus (EBV). This malignant tumor poses a serious public health problem in many countries, especially in Southeast Asia and North Africa where the recorded incidence are highest. During the past decade, a growing number of studies were undertaken to define the molecular basis of NPC. However, the analysis of several clinical and biological parameters of North African and Southeast Asian NPCs has shown notable differences, suggesting that they could result from a distinct combination of etiological factors. One intriguing characteristic of North African NPC, concerns its bimodal age distribution with a secondary peak of incidence in the range of 15-25 years, not observed in Asian NPC. In this juvenile form of NPC, immuno-histochemistry assay has shown that the two key proteins controlling the apoptotic-survival balance p53 and Bcl-2 are less frequently expressed whereas the transmembrane tyrosine-kinase receptor c-kit and the main EBV oncoprotein LMP1 were more abundant. In addition, the EBV serological alterations are less informative for the diagnosis of the juvenile compared to the adult form. In addition, most North African NPCs contain EBV strains with genetic polymorphisms distinct from those described in the Southeast Asia series (predominance of F, D, H1-H2, XhoI+ and f, C, H, XhoI- respectively). In contrast, studies relating on tumor chromosomal alterations or aberrant promoter methylation result in data very similar to those obtained from the Southeast Asia series, supporting the concept of a common molecular basis for all NPC regardless of patient geographic origin.

[Juvenile nasopharyngeal carcinoma: anatomoclinic, biologic, therapeutic and evolutive aspects]

Nasopharyngeal carcinoma (NPC) represents one of the most frequent epithelial tumours of the child in intermediate risk regions. In the Maghreb, it represents the first cancer of teenagers of 15-20 years old. The Epstein Barr virus (EBV) is the most important etiologic factor. Its role in the pathogeneses of NPC has been confirmed by several studies. Young NPCs are characterized by a low rate of EBV antibodies and a high level of LMP1 cell expression than in adult's NPC. The undifferentiated carcinoma nasopharyngeal type (UCNT) represents the most frequent histological type. Immunohistochemical analyses of North Africa early onset NPC is characterized by a weak expression of bcl-2 and p53 and a strong expression of LMP1 and c-kit what makes them different from the adult's NPC. Clinically, cervical node involvement is constantly present. Juvenile NPC is characterized by a very important locoregional extension as well as a high rate of distant metastases. More than 15% of patients had metastases at diagnosis. Radiotherapy is still the standard therapy of NPC. Only some retrospectives studies have been published to determine the benefit, the type and the timing of the chemotherapy in the treatment of juvenile NPC. Metastatic relapses constitute the main cause of death at these young patients. An improvement of the prognosis can be waited with concomitant chemotherapy and intensity modulated radiotherapy. However, randomized multi institutional studies are necessary to standardize the treatment of the NPC in childhood.