Analyzing proteasomal subunit expression reveals Rpt4 as a prognostic marker in stage II colorectal cancer.

Colorectal cancer is a leading cause of cancer-related deaths worldwide. Early diagnosis and treatment of colorectal cancer is the key to improving survival rates and as such a need exists to identify patients who may benefit from adjuvant chemotherapy. The dysregulation of the ubiquitin-proteasome system (UPS) has been implicated in oncogenesis and cancer cell survival, and proteasome inhibitors are in clinical use for a number of malignancies including multiple myeloma. In our study, we examined the protein expression of several key components of the UPS in colorectal cancer using immunohistochemistry to determine expression levels of ubiquitinylated proteins and the proteasomal subunits, 20S core and Rpt4 in a cohort of 228 patients with colon cancer. Multivariate Cox analysis revealed that neither the intensity of either ubiquitinylated proteins or the 20S core was predictive in either Stage II or III colon cancer for disease free survival or overall survival. In contrast, in Stage II patients increased Rpt4 staining was significantly associated with disease free survival (Cox proportional hazard ratio 0.605; p = 0.0217). Our data suggest that Rpt4 is an independent prognostic variable for Stage II colorectal cancer and may aid in the decision of which patients undergo adjuvant chemotherapy.

GIST with a twist--upregulation of PDGF-B resulting in metachronous gastrointestinal stromal tumor and dermatofibrosarcoma protuberans.

CASE REPORT: A 61-year-old male was referred following an incidental radiological discovery of an intra-abdominal mass. His medical history included excision of a lumbar dermatofibrosarcoma protuberans (DFSP) 5 years previously. A CT scan of the abdomen revealed a mass arising from the greater curvature of the stomach. Upper GI endoscopy was normal. He underwent successful laparoscopic resection of this mass. MATERIALS AND METHODS: The histology of the abdominal mass revealed a gastrointestinal stromal tumor (GIST) with poor prognostic indicators. Immunohistochemical analysis of the GIST and his previous DFSP was performed. RESULTS: Immunohistochemistry suggested a link between the GIST and his previous DFSP involving the PDGF signalling system. DISCUSSION: Both GIST and DFSP are extremely rare tumors. A mutation in the platelet-derived growth factor receptor alpha (PDGFR-alpha) has been described in 5-15% of GISTs. It has been shown that DFSP is frequently associated with a translocation between PDGF-B (Chr 22) and COL1A1 (Chr 17), causing continuous activation of PDGFR-beta. Literature review confirms that there are no previously reported cases of both of these tumors occurring in the same patient. CONCLUSION: We hypothesize that this patient may have a previously undescribed genetic mutation involving the PDGF signalling system, resulting in these two very rare malignancies. Immunohistochemistry studies confirmed the link on this occasion. Improvements in our understanding of the molecular biology of the PDGF system may novel therapeutic targets in the future.

Cyclooxygenase-2 expression in stromal tumors of the gastrointestinal tract.

Cyclooxygenase (COX) is a key enzyme in the conversion of arachidonic acid to prostaglandins, prostacyclin, and thromboxane. COX-2 is expressed in many epithelial malignancies, particularly those of the gastrointestinal (GI) tract. COX-2 has been implicated in the pathogenesis of cancers and has a significant negative effect on survival. To date, little is known about the expression of COX-2 in nonepithelial tumors. The objective of this study was to evaluate the expression of COX-2 in GI stromal tumors (GISTs). We evaluated 15 GISTs using tissue microarray. Tissue blocks were retrieved and stained with hematoxylin and eosin to evaluate the histological tumor type. In addition, immunohistochemistry was performed for COX-2, the macrophage marker, CD68 (KP-1), and KIT (CD117). Two pathologists then evaluated the tissues to determine the extent and intensity of COX-2 expression. The location of CD68-positive cells, and whether these cells were COX-2 positive, was also evaluated. The results showed that 80% (12 of 15) of the tumors expressed COX-2. Expression was noted in the cytoplasm of the tumor cells, with variable intensity of staining among the tumors. COX-2 was expressed in both epithelial cell and spindle cell tumors, but appeared stronger in epithelial lesions. In mixed lesions, COX-2 was expressed to a greater extent in epithelial areas. There was a greater extent of COX-2 expression in malignant tumors and tumors located within the stomach. Tumor-infiltrating macrophages (CD68-positive cells) were identified in all of the lesions; in 80% of cases, those macrophages also expressed COX-2. This study is the first to demonstrate COX-2 expression in stromal lesions of the GI tract. The enzyme may play a role in the proliferation of these lesions, suggesting the potential use of nonsteroidal anti-inflammatory drugs in treatment.