Adverse Effects of Immune-Checkpoint Inhibitors: A Comprehensive Imaging-Oriented Review

Mimickers of Immune Checkpoint Inhibitor-induced Inflammatory Arthritis

The differential diagnosis of inflammatory arthritis as an immune-related adverse event can be challenging as patients with cancer can present with musculoskeletal symptoms that can mimic arthritis because of localized or generalized joint pain. In addition, immune checkpoint inhibitors can exacerbate joint conditions such as crystal-induced arthritis or osteoarthritis, or induce systemic disease that can affect the joints such as sarcoidosis. This distinction is important as the treatment of these conditions can be different from that of immune-related inflammatory arthritis.

Acute pancreatitis associated with pembrolizumab-induced hypertriglyceridemia

INTRODUCTION

Acute pancreatitis (AP) following drug-induced hypertriglyceridemia is a rare clinical phenomenon. Immune checkpoint inhibitors have revolutionized treatment for a variety of solid organ and hematological malignancies. Pembrolizumab is a programmed cell death receptor-1 (PD-1) inhibitor that has shown promising responses in many advanced cancers. However, a constellation of immune-related adverse events has also been described. There are reports of pembrolizumab-induced hypertriglyceridemia, but AP as a result of this side effect remains an exceedingly rare clinical sequela.

CASE REPORT

We delineate a case of a patient with stage IVB non-small-cell lung cancer who developed progressive abdominal pain and nausea following administration of pembrolizumab for four months. Laboratory studies revealed increased serum lipase and triglyceride levels at 12,562 IU/L and 16,901 mg/dL, respectively. The diagnosis of AP was made based on the revised Atlanta classification criteria. After ruling out alternative causes, pembrolizumab-induced hypertriglyceridemia was considered the likely etiology of AP.

MANAGEMENT AND OUTCOME

The patient was transferred to the medical intensive care unit for close monitoring. Treatment was initiated with intravenous fluids, pain medications, and an insulin infusion. However, her hypertriglyceridemia levels remained persistently elevated, necessitating therapeutic apheresis. She recovered well with no complications after triglyceride apheresis.

DISCUSSION

AP following pembrolizumab-associated hypertriglyceridemia remains a rare clinicopathologic entity. Given the widespread clinical use of immune checkpoint inhibitors, knowledge of such rare adverse events is crucial. Evaluation of serum triglyceride levels before and after initiating pembrolizumab therapy may be mandated, especially in patients with metabolic comorbidities.

Molecular mechanism of specific HLA-A mRNA recognition by the RNA-binding-protein hMEX3B to promote tumor immune escape

Immunotherapy, including immune checkpoint inhibitors and adoptive cell transfer, has obtained great progress, but their efficiencies vary among patients due to the genetic and epigenetic differences. Human MEX3B (hMEX3B) protein is an RNA-binding protein that contains two KH domains at the N-terminus and a RING domain at its C-terminus, which has the activity of E3 ubiquitin ligase and is essential for RNA degradation. Current evidence suggests that hMEX3B is involved in many important biological processes, including tumor immune evasion and HLA-A regulation, but the sequence of substrate RNA recognized by hMEX3B and the functional molecular mechanisms are unclear. Here, we first screened the optimized hMEX3B binding sequence on the HLA-A mRNA and reported that the two tandem KH domains can bind with their substrate one hundred times more than the individual KH domains. We systematically investigated the binding characteristics between the two KH domains and their RNA substrates by nuclear magnetic resonance (NMR). Based on this information and the small-angle X-ray scattering (SAXS) data, we used molecular dynamics simulations to obtain structural models of KH domains in complex with their corresponding RNAs. By analyzing the models, we noticed that on the KH domains' variable loops, there were two pairs of threonines and arginines that can disrupt the recognition of the RNA completely, and this influence had also been verified both in vitro and in vivo. Finally, we presented a functional model of the hMEX3B protein, which indicated that hMEX3B regulated the degradation of its substrate mRNAs in many biological processes. Taken together, our research illustrated how the hMEX3B protein played a key role in translation inhibition during the immune response to tumor cells and provided an idea and a lead for the study of the molecular mechanism and function of other MEX3 family proteins.