Morphological and molecular assessment of apoptotic mechanisms in peripheral neuroblastic tumours

Abstract

Multiple defects in apoptotic pathways have been described in peripheral neuroblastic tumours (NTs). Mitosis -karyorrhexis index (MKI) is a reliable morphological marker identifying favourable and unfavourable NTs. The extent to which apoptotic processes contribute to determine the clinical significance of MKI is still undefined. Apoptosis was investigated in a series of 110 peripheral NTs by comparing MKI to immunohistochemical and molecular apoptotic features. High MKI was found in 55 out of 110 NTs (50%) and was associated with advanced stage (P ¼ 0.007), neuroblastoma (NB) histological category (P ¼ 0.024), MYCN amplification (Po0.001), and poor outcome (P ¼ 0.011). Overall survival probability was 45% in patients with high MKI compared to 73% in patients with low MKI. In the same 110 NTs, the expression of Bcl-2, Bcl-X L , Bax and Mcl-1 was studied by immunohistochemistry, but no significant associations were found with clinicohistological features. Microarray analysis of apoptotic genes was performed in 40 out of 110 representative tumours. No significant association was found between the expression of apoptotic genes and MKI or clinicohistological features. Proliferative activity was assessed in 60 out of 110 representative tumours using Ki67 immunostaining, but no significant correlations with MKI or clinicobiological features were found. In NTs, the combination of apoptosis and proliferation as expressed by MKI is a significant prognostic parameter, although neither of them is per se indicative of the clinicobiological behaviour and outcome.

Original article Proliferation index revisited in neuroblastic tumors

“…The biological nature of karyorrhectic cells is debatable, but a high MKI in stroma-poor tumors is an indicator of poor prognosis [9,10]. The karyorrhectic cells were shown to be either proliferating or undergoing apoptosis [9,25]. Furthermore, a high cellular density of proliferating cells correlates with poor prognosis, whereas a high density of apoptosis indicates a favorable outcome [13].…”

“…Moreover, the assessment of mitotic rate in an NB tumor section is time-consuming and can be difficult to perform due to the specificity of tumor histology. In undifferentiated and poorly differentiated NB, application of the mitotic count is still controversial because of the high cellularity and mutual resemblance of mitotic and karyorrhectic cells [9,10,25].…”

“…PI may be evaluated in the highest staining region (hot spot PI), or as an average count from randomly chosen fields (random PI). Most often Ki67 is evaluated based on the hot spot approach, which is a more reliable procedure [14,15,25,27]. Depending on the type of the tumor, large discrepancies between the number of cells per field and hence random selection of fields for PI evaluation might bias its score and produce unrepeatable results.…”

“…Ewa Iżycka-Świeszewska, Beata Stefania Lipska-Ziętkiewicz, Elżbieta Adamkiewicz-Drożyńska, Wiesława Grajkowska, Blanka Hermann, Ewa Bień, Janusz Limon ate and high MKI) analysis performed on a smaller group of 60 NB tumors, Uccini et al [25] observed such a correlation only in the subgroup of MYCN amplified tumors. Moreover, contrary to MKI, immunohistochemical markers can be assessed not only in the pre-treatment specimens but also in tumors that were resected after inductive chemotherapy [8].…”

“…It was suggested that their assessment might merit inclusion in the panel of diagnostic and prognostic criteria [6,14]. Conversely, a few reports showed no significant correlations of proliferation markers with clinico-biological features in an NB series [25]. Hence, there is still no consensus regarding significance of the proliferation index (PI) in NB.…”