Potential roles of self-reactive T cells in autoimmunity: lessons from cancer immunology

Association between PD-L1 expression and lymph node metastasis in cutaneous squamous cell carcinoma

AIM

To clarify the relationship between programmed cell death ligand 1 (PD-L1) expression in cutaneous squamous cell carcinoma (cSCC) and clinicopathological variables.

METHODS

We examined PD-L1 expression in tumor cells (TCs) and tumor infiltrating immune cells (ICs) in 46 cases of cSCC by immunohistochemistry. In each case, we employed two methods-intensity and proportion scores-to evaluate PD-L1 expression in TCs. For the evaluation of PD-L1 expression in ICs, only the proportion score was used. Association between PD-L1 expression and clinicopathological variables was analyzed using Fisher's exact test.

RESULTS

High intensity scores in TCs were observed in 18 of the 46 cases (39.1%) and low intensity scores were observed in 28 cases (60.9%). Applying the proportions, using cut-off values of ≥1% and 50%, positive scores in TCs were observed in 36 (78.3%) and 20 cases (43.5%), respectively. PD-L1-positive ICs were observed in 29 (63%) and seven cases (15.2%), using cut-off values of ≥1% and 10%, respectively. The high intensity scores in TCs correlated with lymph node metastasis (P = 0.008) and female gender (P = 0.017), although positive proportions in TCs or ICs were not significantly related to lymph node metastasis. A multivariate analysis showed that high intensity of PD-L1 expression in TCs was an independent risk factor for lymph node metastasis.

CONCLUSIONS

The results suggested that high intensity of PD-L1 expression in TCs is associated with lymph node metastasis in cSCC.

mRNA-transfected dendritic cell vaccine in combination with metronomic cyclophosphamide as treatment for patients with advanced malignant melanoma

INTRODUCTION

Vaccination with dendritic cells (DCs) has generally not fulfilled its promise in cancer immunotherapy due to ineffective translation of immune responses into clinical responses. A proposed reason for this is intrinsic immune regulatory mechanisms, such as regulatory T cells (Tregs). A metronomic regimen of cyclophosphamide (mCy) has been shown to selectively deplete Tregs. To test this in a clinical setting, we conducted a phase I trial to evaluate the feasibility and safety of vaccination with DCs transfected with mRNA in combination with mCy in patients with metastatic malignant melanoma (MM). In addition, clinical and immunological effect of the treatment was evaluated.

EXPERIMENTAL DESIGN

Twenty-two patients were enrolled and treated with six cycles of cyclophosphamide 50 mg orally bi-daily for a week every second week (day 1-7). During the six cycles patients received at least 5 × 10⁶ autologous DCs administered by intradermal (i.d.) injection in the week without chemotherapy. Patients were evaluated 12 and 27 weeks and every 3rd mo thereafter with CT scans according to RECIST 1.0. Blood samples for immune monitoring were collected at baseline, at the time of 4th and 6th vaccines. Immune monitoring consisted of IFNγ ELISpot assay, proliferation assay, and flow cytometry for enumeration of immune cell subsets.

RESULTS

Toxicity was manageable. Eighteen patients were evaluable after six cycles. Of these, nine patients had progressive disease as best response and nine patients achieved stable disease. In three patients minor tumor regression was observed. By IFNγ ELISpot and proliferation assay immune responses were seen in 6/17 and 4/17 patients, respectively; however, no correlation with clinical response was found. The percentage of Tregs was unchanged during treatment.

CONCLUSION

Treatment with autologous DCs transfected with mRNA in combination with mCy was feasible and safe. Importantly, mCy did not alter the percentage of Tregs in our patient cohort. There was an indication of clinical benefit; however, more knowledge is needed in order for DCs to be exploited as a therapeutic option.