P53 expression is significantly correlated with high risk of malignancy and epithelioid differentiation in GISTs. An immunohistochemical study of 104 cases

p53 as a biomarker and potential target in gastrointestinal stromal tumors

KIT and PDGFRA play a major role in the oncogenic process in gastrointestinal stroma tumors (GIST) and small molecules have been employed with great success to target the KIT and PDGFRA pathways in this cancer. However, approximately 10% of patients with GIST are resistant to current targeted drug therapy. There is a need to explore other potential targets. Although p53 alterations frequently occur in most cancers, studies regarding p53 in GIST have been limited. The CDKN2A/MDM2/p53 axis regulates cell cycle progression and DNA damage responses, which in turn control tumor growth. This axis is the major event required for transformation from low- to high-risk GIST. Generally, p53 mutation is infrequent in GIST, but p53 overexpression has been reported to be associated with high-risk GIST and unfavorable prognosis, implying that p53 should play a critical role in GIST. Also, Wee1 regulates the cell cycle and the antitumor activity of Wee1 inhibition was reported to be p53 mutant dependent. In addition, Wee1 was reported to have potential activity in GIST through the regulation of KIT protein and this mechanism may be dependent on p53 status. In this article, we review previous reports regarding the role of p53 in GIST and propose targeting the p53 pathway as a novel additional treatment strategy for GIST.

Molecular and Clinicopathological Features of Gastrointestinal Stromal Tumors in Vietnamese Patients

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal neoplasms of the gastrointestinal tract. Management of GIST patients is currently based on clinicopathological features and associated genetic changes. However, the detailed characteristics and molecular genetic features of GISTs have not yet been described in the Vietnamese population.

METHODS

We first identified 155 patients with primary GIST who underwent surgery with primary curative intent between 2011 and 2014 at University Medical Center at Ho Chi Minh City, Vietnam. We evaluated the clinicopathological features and immunohistochemical reactivity to p53 and Ki-67 in these patients. Additionally, KIT genotyping was performed in 100 cases.

RESULTS

The largest proportion of GISTs was classified as high-risk (43.2%). Of the 155 GISTs, 52 (33.5%) were positive for Ki-67, and 58 (37.4%) were positive for p53. The expression of Ki-67 and p53 were correlated with mitotic rate, tumor size, risk assessment, and tumor stage. Out of 100 GIST cases, KIT mutation was found in 68%, of which 62 (91.2%) were found in exon 11, two (2.9%) in exon 9, and four (5.8%) in exon 17. No mutation in exon 13 was identified. Additionally, KIT mutations did not correlate with any clinicopathological features.

CONCLUSIONS

The expression of Ki-67 and p53 were associated with high-risk tumors. Mutations in exon 11 were the most commonly found, followed by exon 17 and exon 9. Additionally, KIT mutation status was not correlated with any recognized clinicopathological features.

Expression of cell cycle regulators and frequency of TP53 mutations in high risk gastrointestinal stromal tumors prior to adjuvant imatinib treatment

Despite of multitude investigations no reliable prognostic immunohistochemical biomarkers in GIST have been established so far with added value to predict the recurrence risk of high risk GIST besides mitotic count, primary location and size. In this study, we analyzed the prognostic relevance of eight cell cycle and apoptosis modulators and of TP53 mutations for prognosis in GIST with high risk of recurrence prior to adjuvant treatment with imatinib. In total, 400 patients with high risk for GIST recurrence were randomly assigned for adjuvant imatinib either for one or for three years following laparotomy. 320 primary tumor samples with available tumor tissue were immunohistochemically analyzed prior to treatment for the expression of cell cycle regulators and apoptosis modulators cyclin D1, p21, p16, CDK4, E2F1, MDM2, p53 and p-RB1. TP53 mutational analysis was possible in 245 cases. A high expression of CDK4 was observed in 32.8% of all cases and was associated with a favorable recurrence free survival (RFS), whereas high expression of MDM2 (12.2%) or p53 (35.3%) was associated with a shorter RFS. These results were independent from the primary KIT or PDGFRA mutation. In GISTs with higher mitotic counts was a significantly increased expression of cyclin D1, p53 and E2F1. The expression of p16 and E2F1 significantly correlated to a non-gastric localization. Furthermore, we observed a significant higher expression of p21 and E2F1 in KIT mutant GISTs compared to PDGFRA mutant and wt GISTs. The overall frequency of TP53 mutations was low (n = 8; 3.5%) and could not be predicted by the immunohistochemical expression of p53. In summary, mutation analysis in TP53 plays a minor role in the subgroup of high-risk GIST before adjuvant treatment with imatinib. Strong expression of MDM2 and p53 correlated with a shorter recurrence free survival, whereas a strong expression of CDK4 correlated to a better recurrence free survival.

Surgical Pathology of Gastrointestinal Stromal Tumors: Practical Implications of Morphologic and Molecular Heterogeneity for Precision Medicine

Gastrointestinal stromal tumor (GIST), the most common mesenchymal neoplasm of the gastrointestinal tract, exhibits diverse histologic and clinical manifestations. With its putative origin in the gastrointestinal pacemaker cell of Cajal, GIST can arise in association with any portion of the tubular gastrointestinal tract. Morphologically, GISTs are classified as spindled or epithelioid, though each of these subtypes encompasses a broad spectrum of microscopic appearances, many of which mimic other histologic entities. Despite this morphologic ambiguity, the diagnosis of GIST is aided in many cases by immunohistochemical detection of KIT (CD117) or DOG1 expression. The natural history of GIST ranges from that of a tumor cured by surgical resection to that of a locally advanced or even widely metastatic, and ultimately fatal, disease. This clinicopathologic heterogeneity is paralleled by an underlying molecular diversity: the majority of GISTs are associated with spontaneous activating mutations in KIT, PDGFRA, or BRAF, while additional subsets are driven by genetic lesions-often inherited-of NF1 or components of the succinate dehydrogenase enzymatic complex. Specific gene mutations correlate with particular anatomic or morphologic characteristics and, in turn, with distinct clinical behaviors. Therefore, prognostication and treatment are increasingly dictated not only by morphologic clues, but also by accompanying molecular genetic features. In this review, we provide a comprehensive description of the heterogenous molecular underpinnings of GIST, including implications for the practicing pathologist with regard to morphologic identification, immunohistochemical diagnosis, and clinical management.

Inactivating Mutations of RB1 and TP53 Correlate With Sarcomatous Histomorphology and Metastasis/Recurrence in Gastrointestinal Stromal Tumors

OBJECTIVES

Loss-of-function mutations in TP53 and CDKN2A have been found at varying frequencies in gastrointestinal stromal tumors (GISTs), while no mutations of RB1 have been reported to date. The aim of the current study was to determine the mutation frequency of TP53, RB1, and CDKN2A in GISTs.

METHODS

A cohort of 83 primary untreated GISTs was analyzed for mutations in TP53, RB1, and CDKN2A by massive parallel sequencing. Tumors with mutations in TP53 and RB1 were analyzed by fluorescence in situ hybridization for the corresponding gene loci.

RESULTS

Two GISTs harbored inactivating mutations in RB1, and two other GISTs displayed inactivating mutations in TP53 All four tumors were KIT mutant high-risk tumors with highly cellular sarcomatous histomorphology and variable combinations of plump spindle cells to epithelioid highly atypical cells and high mitotic activity. Three of these patients developed recurrent or metastatic disease, while the fourth patient showed tumor rupture intraoperatively. The combined overall frequency of TP53 and RB1 mutations was 13% considering high-risk or malignant GISTs.

CONCLUSIONS

TP53 and RB1 mutations seem to be restricted to high-risk/malignant GISTs and occur at an equal although relatively low frequency.

Correlation between P53 expression and malignant risk of gastrointestinal stromal tumors: evidence from 9 studies

PURPOSE

The published data about p53 expression and its potential value in malignant risk of Gastrointestinal Stromal Tumors patients seemed inconclusive. To derive a more precise estimation of the relationship between p53 and Malignant risk of GIST, a meta-analysis was performed.

MATERIALS AND METHODS

Studies have been identified by searching PubMed and Embase. Inclusive criteria were GIST patients, evaluation of p53 expression and malignant risk. The odds ratio (OR) for positive rate of p53 in NIH very low risk group vs. NIH low risk group, the odds ratio (OR) for positive rate of p53 in NIH low risk group vs. NIH Intermediate risk group and the odds ratio (OR) for positive rate of p53 in NIH Intermediate group vs. NIH high risk group were calculated with 95% confidence interval (CI) for each study as an estimation of potential value of p53 in malignant risk of GIST.

RESULTS

A total of 9 studies including 768 patients were involved in this meta-analysis. The meta-analysis of positive rate of p53 in NIH VL group vs. NIH L group did not attain significant difference (OR 0.38 95% CI, 0.11-1.28; P = 0.12 P(heterogeneity) = 0.51). However the overall OR for positive rate of p53 in NIH L group vs. NIH I group revealed that significantly elevated risks of positive p53 in NIH I group were achieved (OR 0.44 95% CI, 0.24-0.82; P = 0.009 P(heterogeneity) = 0.32). The overall OR for NIH I group vs. NIH H group was 0.62 (95% CI, 0.37-1.02; P = 0.06 P(heterogeneity) = 0.25).

CONCLUSION

The results indicate p53 overexpression correlate with the malignant risk increasing of GIST and have a primary and closest relationship within the NIH I risk group of GIST.

Predictive value of p53 expression in the risk of malignant gastrointestinal stromal tumors: Evidence from 19 studies

The current published data on p53 expression and its predictive value in the risk of malignant gastrointestinal stromal tumors (GIST) has are inconclusive. To derive a more precise estimation of the correlation between p53 and the biological behavior of GIST, a meta-analysis was performed. Studies were identified by searching PubMed and Embase. Inclusion criteria were GIST patients, and the evaluation of p53 expression and risk of malignancy. The odds ratio (OR) for a positive rate of p53 in the benign group vs. that in the malignant group and the ORs for the positive rate of p53 in the National Institutes of Health (NIH) very low risk + low risk group (VL+L) vs. the NIH intermediate risk + high risk (I+H) group were calculated with a 95% confidence interval (CI) for each study as an estimation of the predictive value of p53. A total of 19 studies including 1163 patients were involved in this meta-analysis. The overall OR for the positive rate of p53 in the malignant group vs. the benign group revealed that significantly elevated risks of positive p53 in the malignant group were achieved (OR 0.14, 95% CI: 0.06-0.31, P<0.00001, P(heterogeneity)=0.86). Moreover, significantly elevated risks of correlation between p53 expression and the NIH I+H group were achieved in the comparison of the NIH VL+L group vs. the NIH I+H group (OR, 0.25; 95% CI, 0.17-0.38; P<0.00001, P(heterogeneity)=0.04). The results indicate that p53 expression correlates with poor prognosis in GIST and has a close relationship within the NIH I+H group.

Maspin expression in gastrointestinal stromal tumors

Background

To investigate the role of maspin expression in the progression of gastrointestinal stromal tumors, and its value as a prognostic indicator.

Methods

In the study 54 patients with GIST diagnosis were included in Uludag University of Faculty of Medicine, Department of Pathology between 1997-2007. The expression of maspin in 54 cases of gastrointestinal stromal tumor was detected by immunohistochemistry and compared with the clinicopathologic tumor parameters.

Results

The positive expression rates for maspin in the GISTs were 66,6% (36 of 54 cases). Maspin overexpression was detected in 9 of 29 high risk tumors (31%) and was significantly higher in very low/low (78.6%) and intermediate-risk tumors (63.6%) than high-risk tumors.

Conclusions

Maspin expression might be an important factor in tumor progression and patient prognosis in GIST. In the future, larger series may be studied to examine the prognostic significance of maspin in GISTs and, of course, maspin expression may be studied in different mesenchymal tumors.

Advances in pathological diagnosis of gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. The pathogenesis of GIST may be associated with the mutations of oncogenic c-kit or platelet-derived growth factor receptor alpha (PDGFRA). The pathological diagnosis of GIST needs a combined approach of macropathology, histopathology, immunohistochemistry and gene testing. Preoperative diagnosis is very important for patients with GIST, especially for those needing individualized treatment. In this article, we will review the recent advances in pathological diagnosis of GIST and the consensus criteria for risk stratification of GIST. Besides, we will also summarize the molecular biological parameters used for evaluation of the biological behavior of GIST.