Testicular germ cell cancer: recent developments in biology and clinical management

TIMEAS, a promising method for the stratification of testicular germ cell tumor patients with distinct immune microenvironment, clinical outcome and sensitivity to frontline therapies

PURPOSE

With the heterogeneous genetic background, prognosis prediction and therapeutic targets for testicular germ cell tumors (TGCTs) are still unclear. We defined the tumor immune microenvironment activation status (TIMEAS).

METHODS

We collected a total of 314 TGCT patients from four cohorts, including a 48-case microarray. A nonnegative matrix factorization algorithm was applied to identify the "immune factor", derived the top 150 weighted genes to divide patients into immune and non-immune classes, and further separated the immune class into activated and exhausted subgroups by nearest template prediction. Tumor mutant burden, gene mutation, and copy number alteration were compared with our recently developed package "MOVICS". A random forest algorithm was performed to establish a prediction model with fewer genes. Immunohistochemistry staining was performed to identify TIMEAS in the microarray.

RESULTS

We constructed the TIMEAS in the TCGA-TGCT cohort and further validated it in the GSE3218 and GSE99420 cohorts. The immune class contained the activated status of T-lymphocytes, B-lymphocytes, and macrophages, while Treg cells and the WNT/TGFβ signature were more activated in the immune-suppressed subgroup. Patients in the immune-exhausted subgroup had the worst prognosis, and 22.9% of patients in the immune-activated subgroup had KRAS mutations, which might stimulate the response of the immune system and lead to a favorable prognosis. The immune-exhausted group benefited more from chemotherapy, while the immune-activated subgroup responded well to anti-PD-1/PD-L1 therapy. FSCN1 was validated as the target of the immune-exhausted microenvironment by immunohistochemistry.

CONCLUSION

TIMEAS classification can separate TGCT patients; patients in the immune-activated subgroup could benefit more from anti-PD-L1 immunotherapy, and those in the immune-exhausted subgroup are more suitable for chemotherapy.

Testicular cancer in mice: interplay between stem cells and endocrine insults

BACKGROUND

Incidence of type II germ cell tumors (T2GCT) has increased in young men possibly due to fetal/perinatal exposure to estrogenic compounds. Three-fold increased incidence of T2GCT was reported in men exposed in utero to diethylstilbestrol (DES). T2GCT is a development-related disease arising due to blocked differentiation of gonocytes into spermatogonia in fetal testes which survive as germ cell neoplasia in situ (GCNIS) and initiate T2GCT. In our earlier study, T2GCT-like features were observed in 9 out of 10 adult, 100-day-old mice testes upon neonatal exposure to DES (2 μg/pup/day on days 1-5). Neonatal DES exposure affected testicular very small embryonic-like stem cells (VSELs) and spermatogonial stem cells and resulted in infertility, reduced sperm counts and tumor-like changes leading to our postulate that testicular dysgenesis syndrome possibly has a stem cell basis. The present study was undertaken to further characterize testicular tumor in mice testes.

METHODS

DES-exposed mice pups (n = 70) were studied on D100 and after 12 months to understand how T2GCT progresses. Besides histological studies, a carefully selected panel of markers were studied by immuno-fluorescence and qRT-PCR.

RESULTS

DES resulted in either atrophied or highly vascularized, big-sized testes and extra-testicular growth was also observed. GCNIS-like cells with big, vacuolated cytoplasm and increased expression of OCT-4, SSEA-1, SCA-1 and CD166 (cancer stem cells marker) along with reduced c-KIT, MVH and PTEN were evident. Global hypomethylation was found associated with altered expression of Dnmts, Igf2-H19 and Dlk-Meg3 imprinted genes along with reduced expression of Ezh2, cell cycle regulator p57KIP2 and Meg3; however, Pten remained unaltered. Increased expression of PCNA and Ki67 was observed in concert with complete lack of SOX-9 suggesting Sertoli cells independent proliferation.

CONCLUSIONS

Mouse model for T2GCT is described which will have immense potential to understand cancer initiation, cancer stem cells and also to develop effective therapies in future. T2GCT initiates from tissue-resident, pluripotent VSELs due to their altered epigenome. Neonatal exposure to DES blocks differentiation (spermatogenesis) and VSELs get transformed into CD166 positive cancer stem cells that undergo excessive self-renewal and initiate cancer in adult life challenging existing concept of fetal origin of T2GCT.

New perspectives on PPAR, VDR and FXRα as new actors in testicular pathophysiology

The incidence of reproductive disorders is constantly increasing and affects 15% of couples, with male's abnormalities diagnosed in almost half of the cases. The male gonads exert two major functions of the testis with the productions of gametes (exocrine function) and of sexual hormones (endocrine function). In the last decades, next to steroid receptors such as estrogen and androgen receptors, the involvement of other members of the nuclear receptor superfamily have been described such as Steroidogenic factor-1 (SF-1), Nerve growth factor IB (NGFIB), Liver-X-Receptorα (LXRα) and Dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1 (DAX-1). The purpose of this review is to highlight the emerging roles of some members of the nuclear receptor superfamily among which the vitamin-D Receptor (VDR), Peroxisome Proliferator-Activated Receptor (PPAR), Farnesoid-X-Receptor-α (FXRα). We discuss how these receptors could participate to explain male fertility disorders; and their potential to be use as biomarkers or therapeutic targets for management of fertility disorders.

DNA damage measured in blood cells predicts overall and progression-free survival in germ cell tumour patients

Germ cell tumour (GCT) patients who fail to respond to chemotherapy or who relapse have a poor prognosis. Timely and accurately stratifying such patients could optimise their therapy. We identified endogenous DNA damage levels as a prognostic marker for progression-free (PFS) and overall (OS) survival in chemotherapy-naïve GCT patients. In the present study, we have extended our previous results and reviewed the prognostic power of DNA damage level in GCTs. Endogenous DNA damage levels were measured with the comet assay. Receiver operator characteristic analysis was applied to determine the optimal cut-off value and to evaluate its prognostic accuracy. PFS and OS were estimated by the Kaplan-Meier method and compared using the log-rank test. Hazard ratio (HR) estimates were calculated by Cox regression analysis. A cut-off value of 6.34 provided the highest sensitivity and specificity, with area under curve values of 0.813 and 0.814 for disease progression and mortality, respectively. A % DNA in tail > 6.34 was significantly associated with shorter PFS (HR = 9.54, 95 % confidence interval [CI]: 3.43-26.55, p < 0.001) and OS (HR = 14.62, 95 % CI: 3.14-67.95, p = 0.001) by univariate analysis. The prognostic value of DNA damage measurement was confirmed by multivariate models (HR = 6.45, 95 % CI: 2.22-18.75, p = 0.001 for PFS and HR = 9.40, 95 % CI: 1.70-52.09, p = 0.010 for OS), when HR was adjusted for relevant clinical categories. The added prognostic value of DNA damage in combination with International Germ Cell Cancer Collaborative Group (IGCCCG) risk groups has been revealed. Endogenous DNA damage is an independent prognosticator for PFS and OS in GCT patients and its clinical use, particularly in combination with IGCCCG risk groups, may help in stratifying these patients.