Tenascin-C Is Highly Expressed in T-Cell Non-Hodgkin Lymphomas and Represents an Attractive Target for Radioimmunotherapy

Introduction: Tenascins are a family of large glycoproteins present in extracellular matrix, overexpressed in tumors compared to healthy tissues. Tenatumomab (ST2146) is an anti tenascin-C monoclonal antibody that is currently under development for radio immunotherapy (RIT) in tenascin-C expressing cancer. T-cell non-Hodgkin lymphomas (T-NHL) are a heterogeneous and rare group of poor prognosis malignancies lacking of standard treatments. Aim of the study was to evaluate the expression of tenascin-C in a cohort of T-NHL.

Material and Methods: Under an IRB-approved protocol, 100 patients with a diagnosis of T-NHL in charge at the Hematology Unit of "Papa Giovanni XXII" Hospital were included in the study. Paraffin-embedded tumor samples were investigated using standard immunohistochemistry (IHC) for tenascin-C expression using tenatumomab antibody. Slides were assessed by two independent investigators. Staining was scored using the four different levels "no staining", "weak", "moderate" and "strong" (0-3). A grading system was used to express the proportion of involved areas in each case, as follows: 0 (0% to 25%), 1 (26% to 50%), 2 (51% to 75%), 3 (76% to 100%). Pattern of expression (stromal, vascular and/or cytoplasmic) was as well recorded. Tenascin C gene expression data were extracted from publicly available datasets. Association among variables was assessed with Chi square or Fisher exact test.

Results:Of the 100 patients evaluated, 75 cases were peripheral T-NHL (PTCL) and 25 cutaneous T-NHL (CTCL). Specific diagnosis was, anaplastic large cell lymphoma (ALCL) ALK negative (n=21) or positive (n=19), PTCL-not otherwise specified (NOS, n=20), mycosis fungoides (n=13), angioimmunoblastic T-cell lymphoma (AITL, n=9), CD30+ primary cutaneous T-NHL (n=6) and other subtypes (n=12). Tenatumomab revealed the expression of tenascin-C in all the patients, with a staining that was weak, moderate and strong in 21, 51 and 28 of the cases. There was no significant different distribution among histologies (P=0.334). A high (>50%, grade 2-3) proportion of involved areas in pathologic samples were shown in half of the patients and this proportion was higher in ALCL ALK- (81%), AITL (78%) and ALCL ALK+ (58%) while was lower for PTCL NOS (30%) and CTCL (24%) (P=0.0019). A stromal pattern of expression was present in all the cases, vasculature was stained in 47 patients while in 21 tenascin-C was as well cytoplasmic. Vascular pattern was revealed in 56% of PTCL and 20% of CTCL (P=0.0018). To further evaluate the presence of tenascin C in T-NHL, gene expression datasets from published reports were retrieved and expression values of tenascin-C gene were extracted. Significant overexpression was present in T-NHL compared to normal tissues in both of the two considered datasets (Piccaluga et al., 2007 and Iqbal et al., 2010).

Conclusions: Tenatumomab revealedthat tenascin-C is uniformly present in T-NHL with a high proportion of cases showing a strong and diffuse expression. Thus, tenascin-C represent an attractive target for RIT in this category of poor prognosis rare diseases.