A Systematic Review of Immunotherapy in Urologic Cancer: Evolving Roles for Targeting of CTLA-4, PD-1/PD-L1, and HLA-G

CONTEXT

Overexpression of immune checkpoint molecules affects tumor-specific T-cell immunity in the cancer microenvironment, and can reshape tumor progression and metastasis. Antibodies targeting checkpoints could restore antitumor immunity by blocking the inhibitory receptor-ligand interaction.

OBJECTIVE

To analyze data and current trends in immune checkpoint targeting therapy for urologic cancers.

EVIDENCE ACQUISITION

Systematic literature search for clinical trials in the PubMed and Cochrane databases up to August 2014 according to Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Endpoints included oncologic results, tumor response rates, safety, and tolerability.

EVIDENCE SYNTHESIS

Anti-CTLA-4 monotherapy has demonstrated biochemical responses in prostate cancer. One phase 3 trial assessing ipilimumab efficacy in castration-resistant disease was negative overall. Nevertheless, ipilimumab may significantly improve overall survival compared with placebo in subgroups of patients with favorable prognostic features. In renal cancer, phase 1 trials showed interesting stabilization or long-lasting objective response rates approaching 50% using anti-PD-1/PD-L1 drugs in heavily pretreated metastatic patients. In bladder cancer, one phase 2 trial indicated a good safety profile for ipilimumab as a neoadjuvant drug before radical cystectomy. Overall, immune-related effects such as colitis and dermatitis were common and well tolerated.

CONCLUSIONS

Our systematic review shows that antibodies blocking immune checkpoints offer interesting and long-lasting response rates in heavily pretreated patients with advanced urologic cancers. More promising results are currently provided by anti-CTLA-4 antibodies in prostate cancer and by PD-1/PD-L1 inhibitors in renal cancer. These should encourage new clinical trials of immune therapy combinations and immunotherapy monotherapy combined with conventional anticancer drugs. In bladder cancer, the use of targeted immunotherapy still remains underevaluated; however, preliminary results reported at recent conferences seem encouraging.

PATIENT SUMMARY

Data from studies support the activity and safety of immune checkpoint inhibitors in urologic cancers, alone or in combination with conventional cancer therapies. Encouraging data in other oncologic fields could translate into interesting responses in urological cancers.

Programmed death ligand-1 expression in adrenocortical carcinoma: an exploratory biomarker study

BACKGROUND

Adrenocortical carcinoma (ACC) is a rare tumor in which prognostic factors are still not well established. Programmed Death Ligand-1 (PD-L1) expression in ACC and its association with clinico-pathological features and survival outcomes are unknown.

METHODS

Formalin-fixed paraffin-embedded (FFPE) specimens were obtained from 28 patients with ACC. PD-L1 expression was evaluated by immunohistochemistry (IHC) in both tumor cell membrane and tumor infiltrating mononuclear cells (TIMC). PD-L1 positivity on tumor cells was defined as ≥5% tumor cell membrane staining. TIMC were evaluated by IHC using a CD45 monoclonal antibody. For PD-L1 expression in TIMC, a combined score based on the extent of infiltrates and percentage of positive cells was developed. Any score greater that zero was considered PD-L1 positive. Baseline clinico-pathological characteristics and follow up data were retrospectively collected. Comparisons between PD-L1 expression and clinico-pathological features were evaluated using unpaired t-test and Fisher's exact test. Kaplan-Meier method and log-rank test were used to assess association between PD-L1 expression and 5-year overall survival (OS).

RESULTS

Among 28 patients with surgically treated ACC, 3 (10.7%) were considered PD-L1 positive on tumor cell membrane. On the other hand, PD-L1 expression in TIMC was performed in 27 specimens and PD-L1 positive staining was observed in 19 (70.4%) patients. PD-L1 positivity in either tumor cell membrane or TIMC was not significantly associated with higher stage at diagnosis, higher tumor grade, excessive hormone secretion, or OS.

CONCLUSIONS

PD-L1 expression can exist in ACC in both tumor cell membrane and TIMC with no relationship to clinico-pathologic parameters or survival.

Association of PD-L1 expression on tumor-infiltrating mononuclear cells and overall survival in patients with urothelial carcinoma

BACKGROUND

Programmed death-1 (PD-1) receptor/PD-1 ligand (PD-L1) pathway negatively regulates T-cell-mediated responses. The prognostic impact of PD-L1 expression needs to be defined in urothelial carcinoma (UC).

PATIENTS AND METHODS

Formalin-fixed paraffin-embedded tumor samples from 160 patients with UC were retrieved. PD-L1 expression was evaluated by immunohistochemistry using a mouse monoclonal anti-PD-L1 antibody (405.9A11). PD-L1 positivity on tumor cell membrane was defined as ≥5% of tumor cell membrane staining. The extent of tumor-infiltrating mononuclear cells (TIMCs) as well as PD-L1 expression on TIMCs was scored from 0 to 4. A score of 2, 3, or 4 was considered PD-L1-positive. Clinico-pathological variables were documented. The Cox regression model was used to assess the association of PD-L1 expression with overall survival (OS) in patients who developed metastases.

RESULTS

TIMCs were present in 143 of the 160 patient samples. Out of 160 samples, 32 (20%) had positive PD-L1 expression in tumor cell membrane. Out of 143 samples with TIMCs, 58 (40%) had positive PD-L1 expression in TIMCs. Smoking history, prior BCG use and chromosome 9 loss did not correlate with PD-L1 expression in either tumor cell membrane or TIMCs. PD-L1 positivity was not different between non-invasive or invasive UC. In patients who developed metastases (M1) and were treated with systemic therapy (n = 100), PD-L1 positivity on tumor cell membrane was seen in 14% of patients and did not correlate with OS (P = 0.45). Out of 89 M1 patients who had evaluable PD-L1 on TIMCs, PD-L1 expression was seen in 33% of patients and was significantly associated with longer OS on multivariate analysis (P = 0.0007).

CONCLUSION

PD-L1 is widely expressed in tumor cell membrane and TIMCs in UC. PD-L1 in tumor cells was not predictive of OS. However, positive PD-L1 expression in TIMCs was significantly associated with longer survival in those patients who developed metastases.