Arginase-producing myeloid suppressor cells in renal cell carcinoma patients: a mechanism of tumor evasion

Myeloid suppressor cells with high arginase activity are found in tumors and spleen of mice with colon and lung cancer. These cells, described as macrophages or immature dendritic cells, deplete arginine and impair T cell proliferation and cytokine production. Although arginase activity has been described in cancer patients, it is thought to originate from tumor cells metabolizing arginine to ornithine needed to sustain rapid cell proliferation. The goal of this study was to determine whether myeloid suppressor cells producing high arginase existed in renal cell carcinoma patients. Peripheral blood mononuclear cells from 123 patients with metastatic renal cell carcinoma, prior to treatment, were found to have a significantly increased arginase activity. These patients had a markedly decreased cytokine production and expressed low levels of T cell receptor CD3zeta chain. Cell separation studies showed that the increased arginase activity was limited to a specific subset of CD11b+, CD14-, CD15+ cells with a polymorphonuclear granulocyte morphology and markers, instead of macrophages or dendritic cells described in mouse models. Furthermore, these patients had low levels of arginine and high levels of ornithine in plasma. Depletion of the CD11b+, CD14- myeloid suppressor cells reestablished T cell proliferation and CD3zeta chain expression. These results showed, for the first time, the existence of suppressor myeloid cells producing arginase in human cancer patients. In addition, it supports the concept that blocking arginase may be an important step in the success of immunotherapy.

Carbonic anhydrase IX expression predicts outcome of interleukin 2 therapy for renal cancer

PURPOSE

Renal cancer response to interleukin 2 (IL-2) therapy and patient survival has been correlated with tumor histology and carbonic anhydrase IX (CAIX) expression. In an effort to confirm and expand these observations, we examined CAIX expression in pathology specimens from renal cancer patients who had previously received IL-2 therapy.

EXPERIMENTAL DESIGN

Paraffin-embedded tissue sections of renal cancer were immunostained with the MN-75 monoclonal antibody to CAIX and expression levels were correlated with histologic findings and clinical outcome.

RESULTS

Tissue specimens were obtained from 66 patients; 27 of whom (41%) had responded to IL-2-based therapy. Fifty-eight specimens were assessed as clear cell, with 56, 33, and 4 having alveolar, granular, and papillary features, respectively. Twenty-four (36%), 31 (47%), and 11 (17%) were classified into good, intermediate, and poor prognosis groups according to the Upton pathology model. Forty-one specimens (62%) had high CAIX expression. Twenty-one of 27 (78%) responding patients had high CAIX expressing tumors compared with 20 of 39 (51%) nonresponders (odds ratio, 3.3; P = 0.04). Median survival was prolonged (P = 0.04) and survival >5 years was only seen in high CAIX expressers. In patients with intermediate pathologic prognosis, all nine responders had high CAIX expression versus 11 of 22 nonresponders. A resultant group with good pathologic prognosis alone or with intermediate pathologic prognosis and high CAIX contained 26 of 27 (96%) responders compared with 18 of 39 (46%) nonresponders (odds ratio, 30; P < 0.01) and exhibited longer median survival (P < 0.01).

CONCLUSIONS

CAIX expression seems to be an important predictor of outcome in renal cell carcinoma patients receiving IL-2-based therapy and may enhance prognostic information obtained from pathology specimens.

Histologic Predictors of Renal Cell Carcinoma Response to Interleukin-2-Based Therapy

The authors examined pathology from patients with renal cancer (RCC) treated with IL-2 to determine response rates for clear cell and variant RCC and to identify histologic features that predict response. Pathology specimens were reviewed by a single pathologist who was blinded to both the prior pathology interpretation and the therapeutic response. Findings were correlated with response to IL-2 therapy. Evaluable pathology specimens were obtained from 231 patients. Of 163 primary RCCs, the response rate was 21% (30/146) for patients with clear cell versus 6% (1/17) for patients with variant or indeterminate type RCC (P = 0.20). For clear cell carcinomas, response to IL-2 was associated with the presence of alveolar features and the absence of papillary and granular features. Patients with more than 50% alveolar features and no granular or papillary features had a 39% response rate (14/36). Patients with alveolar and granular features representing less than 50% of the specimen and no papillary features had a 19% response rate (15/77). The response rate for the others was 3% (1/33). This model was then applied to an independent sample of 68 metastasis specimens. Response rates in the three prognostic groups and for patients with non-clear cell cancers were 25% (5/20), 9% (2/22), 0% (0/16), and 0% (0/10), respectively. Median survivals for all patients with clear cell tumors by risk group were 2.87, 1.36, and 0.87 years, respectively (P < 0.001). These data suggest that patients with non-clear cell RCC or with clear cell RCC with papillary, no alveolar, and/or more than 50% granular features respond poorly to IL-2 and should be considered for alternative treatments. Investigation of other tumor-related predictors of IL-2 responsiveness is warranted.

Potential histologic and molecular predictors of response to temsirolimus in patients with advanced renal cell carcinoma

PURPOSE

Similar to other molecularly targeted agents, temsirolimus, an inhibitor of mammalian target of rapamycin, has shown promising activity in advanced renal cell carcinoma. However, only a subset of patients appears to derive significant tumor responses. In an effort to identify potential predictors of response to temsirolimus, tumor samples from a subset of patients within a randomized phase II trial of temsirolimus in advanced renal cell carcinoma were studied.

PATIENTS AND METHODS

Paraffin-embedded tissue sections from patients who had received temsirolimus were immunostained with antibodies to carbonic anhydrase IX, phospho-S6, phospho-Akt (pAkt), and phosphotase and tensin homologue. Expression levels were correlated with objective response (partial response [PR], minor response [MR]) and clinical benefit (PR, MR, SD>or=4 cycles) to temsirolimus. In addition, von Hippel-Lindau (VHL) mutational analysis was performed and correlated with response.

RESULTS

Tissue specimens were obtained from 20 patients who were evaluable for both tumor response and staining for phospho-S6 and carbonic anhydrase IX. In addition, 19 specimens were evaluable for pAkt, and 18 for phosphotase and tensin homologue. VHL mutational analysis was performed on 16 samples. Five patients achieved an objective response (1 PR/4 MRs) to temsirolimus. There was a positive association of phospho-S6 expression (P=.02) and a trend toward positive expression of pAkt (P=.07) with response to temsirolimus. No patient without high expression of either phospho-S6 or pAkt experienced an objective tumor response. There was no correlation of carbonic anhydrase IX and phosphotase and tensin homologue expression or VHL status with response to temsirolimus.

CONCLUSION

These results suggest that phospho-S6 and pAkt expression are promising predictive biomarkers for response to temsirolimus that are worthy of further exploration for use in patient selection models for mammalian target of rapamycin inhibitors.