Overexpression of Numb suppresses tumor cell growth and enhances sensitivity to cisplatin in epithelioid malignant pleural mesothelioma

Our plain-English summary of Overexpression of Numb suppresses tumor cell growth and enhances sensitivity to cisplatin in epithelioid malignant pleural mesothelioma, by Y. Kang, M. Ding, G. Tian, et al (Oncology Reports, 2013).

The study

• Authors: Y. Kang, M. Ding, G. Tian, H. Guo, Y. Wan, Z. Yao, B. Li, D. Lin
• Journal: Oncology Reports
• Published: 2013;30(1):313-9
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Malignant pleural mesothelioma (MPM) is a highly aggressive and conventional treatment-resistant tumor with a dismal prognosis. Among the three histological subtypes of MPM, the epithelioid is the most common type. Numb is considered as a tumor suppressor playing a critical role in controlling asymmetric cell division, maintenance of stem cell compartments, ubiquitination of specific substrates and regulating Notch-, Hedgehog- and TP53-activated pathways. The present study was designed to analyze the role of Numb in epithelioid MPM. We investigated the expression of Numb in 39 epithelioid MPM and 22 normal pleural tissues by immunohistochemistry. Furthermore, we overexpressed Numb in NCI-H2452, an epithelioid human MPM cell line, and investigated the effect of Numb overexpression on the proliferation, apoptosis and sensitivity to cisplatin in cells. The expression of Numb was significantly lower in MPM compared to the control group and Numb had an inverse correlation with the ki-67 labeling index. Loss of Numb expression was associated with poor prognosis in epithelioid MPM. Overexpression of Numb in NCI-H2452 cells significantly inhibited proliferation, promoted apoptosis and enhanced sensitivity to cisplatin. Moreover, Numb overexpression activated caspase-9 and caspase-3 through release of cytochrome c as well as downregulation of XIAP and survivin. We speculate that cytochrome c/caspase signaling is a possible mechanism through which Numb enhances the apoptosis of NCI-H2452 cells. These results suggest that Numb may be involved in epithelioid MPM development, and its upregulation may confer sensitivity to cisplatin, suggesting potential therapeutic options for MPM.

In plain English

This Chinese laboratory study examined a protein, Numb, in epithelioid malignant pleural mesothelioma (MPM). The authors stained tumors from 39 patients and 22 normal pleural samples. The text reports Numb in 20/39 (51.3%) tumors and 19/22 (86.4%) normal samples, though the paper's table counts 20 tumors as negative. Lower Numb was linked to a higher Ki-67 index, a cell-growth marker. In a univariate analysis of 32 patients with follow-up, median survival was 10.3 months (95% CI 9.1-11.5) for Numb-negative tumors and 11.7 months (95% CI 11.1-12.3) for Numb-positive tumors (log-rank P less than 0.05). The authors made one epithelioid MPM cell line, NCI-H2452, produce extra Numb. These cells grew less at 48 and 72 hours. More died by programmed cell death (apoptosis): 19.88% versus 9.41% in control cells, and 32.33% versus 16.04% with 5 µmol/l cisplatin. The authors concluded that Numb was frequently reduced in epithelioid MPM, that this reduction was associated with poor prognosis, and that Numb sensitized these cells to cisplatin. They said the mechanisms need further study. Asbestos exposure was not examined.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory study combining staining of patient tumor and normal pleural tissue (immunohistochemistry, with retrospective univariate survival analysis) and experiments on a cultured mesothelioma cell line
• Who was studied: Tissue from 39 patients with epithelioid MPM who underwent medical thoracoscopy at Shandong Provincial Hospital, China, 2007 to 2010 (median age 55, 19 men, 20 women), plus 22 normal pleural samples as controls. Laboratory experiments used the human epithelioid MPM cell line NCI-H2452.
• Exposure: No asbestos or other environmental exposure was studied. In the cell experiments, NCI-H2452 cells were made to overexpress Numb and were treated with cisplatin at 1 to 10 µmol/l.
• Main results:
  • The results text reports Numb positive in 51.3% (20/39) of epithelioid MPM tumor samples, with weaker staining, compared with 86.4% (19/22) of normal pleural specimens (P less than 0.05). However, Table I lists the 39 tumors as 20/10/6/3 in grades 0/1/2/3. Grade 0 is defined as no staining or under 10% of cells, which is negative under the paper's 10% cut-off, so the table implies 20 negative and 19 positive tumors.
  • In the tumors, Numb expression was inversely correlated with the Ki-67 labeling index (P less than 0.05; Table I gives P = 0.011).
  • In the tumors, loss of Numb was not correlated with gender, age or ECOG performance status.
  • Among the 32 patients with complete follow-up (30 had died by July 2011; median follow-up 11.3 months), a univariate analysis found median overall survival of 10.3 months (95% CI 9.1-11.5) for Numb-negative tumors (grade 0). It was 11.7 months (95% CI 11.1-12.3) for tumors with grade 1-3 Numb expression (log-rank P less than 0.05).
  • NCI-H2452 cells overexpressing Numb had lower viability than control (mock-transfected) cells at 48 and 72 hours. There was no significant difference at 24 hours.
  • Without cisplatin, apoptosis at 72 hours was 19.88 plus or minus 3.31% in Numb-overexpressing cells versus 9.41 plus or minus 2.34% in control cells (P less than 0.05).
  • Numb-overexpressing cells treated with cisplatin at 1-10 µmol/l for 24 hours had significantly lower viability than control cells.
  • After 5 µmol/l cisplatin for 24 hours, apoptosis was 32.33 plus or minus 5.64% in Numb-overexpressing cells versus 16.04 plus or minus 3.20% in control cells (P less than 0.05).
  • Numb-overexpressing cells showed more activated caspase-3 and caspase-9, release of cytochrome c into the cytoplasm, and lower levels of XIAP and survivin. These are proteins involved in controlling cell death.
• The authors' conclusion: The authors concluded that Numb was frequently reduced in epithelioid MPM and that this reduction was associated with poor prognosis. They reported that extra Numb inhibited growth, promoted apoptosis and sensitized NCI-H2452 cells to cisplatin. They speculated that cytochrome c/caspase signaling was a possible mechanism and said further investigation is warranted.
• Limitations the authors state:
  • The authors stated that the mechanism by which Numb lowered XIAP and survivin is unknown, and that their proposed mechanism needs further study.
  • The authors stated that the cause of Numb protein loss in NCI-H2452 cells needs further exploration. They speculated that it happens through protein degradation.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Cisplatin, Epithelioid, Pleural Mesothelioma, Prognosis, Histological Subtype, STEM, Immunohistochemistry, Apoptosis.

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