Management of Refractory Germ Cell Cancer

Targeting oncogenic microRNAs from the miR-371~373 and miR-302/367 clusters in malignant germ cell tumours causes growth inhibition through cell cycle disruption

BACKGROUND

MiR-371~373 and miR-302/367 cluster over-expression occurs in all malignant germ cell tumours (GCTs), regardless of age (paediatric/adult), site (gonadal/extragonadal), or subtype [seminoma, yolk sac tumour (YST), embryonal carcinoma (EC)]. Six of eight microRNAs from these clusters contain the seed sequence 'AAGUGC', determining mRNA targeting. Here we sought to identify the significance of these observations by targeting these microRNAs functionally.

METHODS

We targeted miR-371~373 and/or miR-302/367 clusters in malignant GCT cell lines, using CRISPR-Cas9, gapmer primary miR-302/367 transcript inhibition, and peptide nucleic acid (PNA) or locked nucleic acid (LNA)-DNA inhibition targeting miR-302a-d-3p, and undertook relevant functional assays.

RESULTS

MiR-302/367 cluster microRNAs made the largest contribution to AAGUGC seed abundance in malignant GCT cells, regardless of subtype (seminoma/YST/EC). Following the unsuccessful use of CRISPR-Cas9, gapmer, and PNA systems, LNA-DNA-based targeting resulted in growth inhibition in seminoma and YST cells. This was associated with the de-repression of multiple mRNAs targeted by AAGUGC seed-containing microRNAs, with pathway analysis confirming predominant disruption of Rho-GTPase signalling, vesicle organisation/transport, and cell cycle regulation, findings corroborated in clinical samples. Further LNA-DNA inhibitor studies confirmed direct cell cycle effects, with an increase of cells in G0/G1-phase and a decrease in S-phase.

CONCLUSION

Targeting of specific miR-371~373 and miR-302/367 microRNAs in malignant GCTs demonstrated their functional significance, with growth inhibition mediated through cell cycle disruption.

The Use of Salvage Chemotherapy for Patients with Relapsed Testicular Germ Cell Tumor (GCT) in Canada: A National Survey

BACKGROUND

Although metastatic germ cell tumor (GCT) is highly curable with initial cisplatin-based chemotherapy (CT), 20-30% of patients relapse. Salvage CT options include conventional (CDCT) and high dose chemotherapy (HDCT), however definitive comparative data remain lacking. We aimed to characterize the contemporary practice patterns of salvage CT across Canada.

METHODS

We conducted a 30-question online survey for Canadian medical and hematological oncologists with experience in treating GCT, assessing treatment availability, patient selection, and management strategies used for relapsed GCT patients.

RESULTS

There were 30 respondents from 18 cancer centers across eight provinces. The most common CDCT regimens used were TIP (64%) and VIP (25%). HDCT was available in 13 centers (70%). The HDCT regimen used included carboplatin and etoposide for two cycles (76% in 7 centers), three cycles (6% in 2 centers), and the TICE protocol (11%, in 2 centers). "Bridging" CDCT was used by 65% of respondents. Post-HDCT treatments considered include surgical resection for residual disease (87.5%), maintenance etoposide (6.3%), and surveillance only (6.3%).

CONCLUSIONS

HDCT is the most commonly used GCT salvage strategy in Canada. Significant differences exist in the treatment availability, selection, and delivery of HDCT, highlighting the need for standardization of care for patients with relapsed testicular GCT.

Current Management of Refractory Germ Cell Tumors

PURPOSE OF REVIEW

Germ cell tumors (GCTs) are the most common solid tumors affecting men between ages of 20 and 34 years. Most of the cases, even in advanced disease, will have good prognosis. However, around 20-30% of advanced disease will be refractory or develop relapse after treatment. Herein, we review the current management of refractory/relapsed GCTs.

RECENT FINDINGS

Salvage treatment of GCTs has been a controversial topic for the last few decades. Conventional dose chemotherapy (CDCT), high-dose chemotherapy (HDCT) with stem cell infusion, and surgical salvage were proven to be effective and curative options in some cases. The international randomized trial (TIGER) will ultimately answer which chemotherapy approach may be optimal. Furthermore, the usage of immunotherapy is still under investigation with limited data so far in the setting of relapsed/refractory GCTs. Curative paradigms including with CDCT and HDCT are possible, although novel approaches beyond HDCT are still needed to eliminate mortality from this disease.

[Intensification by high dose chemotherapy for germ-cell tumors, still an ongoing subject?]

More than 80 % of patient with metastatic germ cell tumor are cured with first line chemotherapy. Twenty to 30 % of patients will experience relapse or refractory disease with a very poor long-term prognosis. Most of them had metastatic germ cell tumors with a poor prognosis according to the international germ cell classification collaborative group (IGCCCG). The role of treatment intensification by high dose chemotherapy (HDCT) followed by stem cell rescue has not been demonstrated yet in the first line setting compared to standard chemotherapy. The role of HDCT in first or second salvage is also not yet demonstrated, many studies have been published in this situation with a lot of different regimen. Outside clinical trial, HDCT remains an option in salvage therapy, depending on many factors including prognostics factors, previous therapy, general condition and reference center consideration to select eligible patient who could benefit the most of this approach. Results from the international randomized trial TIGER will provide evidence-based information for HDCT strategy.

Surgical treatment of metastatic germ cell cancer

Among young men between the ages of 15 and 40 years, germ cell cancer is the most common solid tumor [1]. The worldwide incidence of germ cell cancer is 70 000 cases. Compared to all solid tumors of men, germ cell cancer accounts for 1% of all male tumors. Nevertheless, the mortality of this rare tumor entity is about 13% since 9507 patients died worldwide of germ cell cancer. The improvement in survival of germ cell cancer patients is due to a multimodal treatment of germ cell cancer including cisplatin-based chemotherapy and surgery leading to higher cure-rates even in advanced stages [1], whereas the increasing incidence of germ cell cancers cannot be thoroughly explained. In this article we review the current indications for surgery in metastatic germ cell cancers, highlight the strength and weaknesses of techniques and indications and raise the question how to improve surgical treatment in metastatic germ cell cancer.