Using advanced technology, scientists at Chan Zuckerberg (CZ) Biohub, Mayo Clinic and University of California, San Francisco (UCSF), have discovered an autoimmune disease that appears to affect men with testicular cancer.
Called “testicular cancer-associated paraneoplastic encephalitis,” the disease causes severe neurological symptoms in men.
They progressively lose control of their limbs, eye movements, and, in some cases, speech.
The disease begins with a testicular tumor, which appears to cause the immune system to attack the brain.
Affected men often find themselves misdiagnosed or undiagnosed and appropriate treatment is delayed.
In a study published in The New England Journal of Medicine, the scientists identified a highly specific and unique biomarker for the disease by using a variation of “programmable phage display” technology.
Their refined version of this technology simultaneously screens more than 700,000 autoantibody targets across all human proteins.
Using this powerful tool, the UCSF researchers evaluated cerebrospinal fluid from a 37-year-old man who had a history of testicular cancer and debilitating neurological symptoms, including vertigo, imbalance and slurred speech.
The enhanced phage technology identified autoantibodies targeting Kelch-like protein 11 (KLHL11), which is found in the testes and parts of the brain.
These results were correlated and validated with additional patient samples from the Mayo Clinic.
In addition to identifying the cause of this mysterious neurological disease, the results point the way to using this protein biomarker as a diagnostic test for men with testicular cancer-associated paraneoplastic encephalitis.
“Mayo Clinic’s Neuroimmunology Laboratory has a long history of biomarker discovery, and this continues that tradition, bringing together Mayo Clinic’s biobank, the largest repository of biospecimens in the world, with advanced technologies being devised and implemented at UCSF and CZ Biohub,” says Sean Pittock, M.D., a Mayo Clinic neurologist and corresponding author of the study. “By working together, our organizations have the potential to make biomarker discoveries much more rapidly.”
Dr. Pittock is director of Mayo Clinic’s Neuroimmunology Laboratory and the Marilyn A. Park and Moon S. Park, M.D., Director of the Center for Multiple Sclerosis and Autoimmune Neurology.
From darkroom to discovery
Mayo Clinic’s Neuroimmunology Laboratory annually screens about 150,000 patients for autoimmune neurological diseases by applying patients’ biospecimen samples – serum or cerebrospinal fuid – to thin slices of brain tissue from mice.
Some patients with autoimmune neurological diseases harbor antibodies that bind to tissue with a specific pattern of staining.
About 20 years ago, Mayo scientists first identified a staining pattern that researchers dubbed “sparkles” because, in a darkroom under a microscope, the patient’s sample looked like stars shining dimly in the night sky, Dr. Pittock says.
The male patient had ataxia – poor coordination, involuntary eye movements, change in speech – and turned out to have testicular cancer.
Over the years, the Mayo lab occasionally identified the sparkles pattern, and the patients’ clinical stories were the same: ataxia and testicular cancer. But the pattern was faint and easy to miss, and an autoantibody target remained elusive.
A UCSF team led by Joe DeRisi, Ph.D., a biochemist and co-president of Chan Zuckerberg Biohub, and Michael Wilson, M.D., neurologist and member of the UCSF Weill Institute for Neurosciences, developed a customized version of phage technology that identified KLHL11 as the target for testicular cancer-associated paraneoplastic encephalitis based on a patient’s sample. The enhanced phage technology builds on work pioneered in the laboratory of Stephen Elledge, Ph.D., at Harvard Medical School.
The collaborative effort reported in the new paper was spearheaded by co-first authors Caleigh Mandel-Brehm, Ph.D., a UCSF postdoctoral researcher, and Divyanshu Dubey, M.B.B.S., a Mayo Clinic neurologist and lab medicine physician. Analyses were conducted on biospecimens of 12 additional men with similar medical histories. All were positive for autoantibodies targeting KLHL11.
Using this biomarker signature, 37 patients now have been diagnosed with this paraneoplastic disease, and the scientists believe many more will be diagnosed.
“This study is the tip of the iceberg,” Dr. DeRisi says. “We know there are more paraneoplastic autoimmune diseases waiting to be discovered and more people to help.”
“For roughly half the patients with paraneoplastic or autoimmune causes of encephalitis, the protein being targeted has yet to be identified,” Dr. Wilson says.
“Building on the Elledge lab’s work, we hope to tackle that problem head-on with this technology for finding antibodies, so we can potentially add to the number of diseases that are known, and help patients and families get diagnoses more quickly.”
Study implications
Physicians who suspect a patient may have this form of paraneoplastic encephalitis currently can work with Mayo Clinic to screen for KLHL11.
“Early diagnosis is extremely important,” Dr. Dubey says. “If we diagnose patients early, we can start them on immunosuppressive medications.
The sooner we can prevent this damage from happening, the sooner we can stop the disease progression and the better chance we have for clinical improvement in the patient’s life.”
In an epidemiological assessment included in the study, the prevalence of KLHL11 encephalitis in Olmsted County, Minnesota, home to Mayo Clinic’s Rochester campus, was nearly 3 per 100,000 men.
Thus, KLHL11 is one of the more common autoimmune encephalitis biomarkers found in Olmsted County, and likely elsewhere in the U.S. and beyond.
Testicular cancer is a relatively rare malignancy affecting younger men with an estimated 9,310 men in the United States diagnosed and 400 going on to die of their disease in 2018 (1,2).
A majority (68%) of testicular cancer is diagnosed while still localized (T1 disease), however, 19% will have disease spread to the regional lymph nodes and 12% will have distant metastases at the time of diagnosis (1).
The presence, or absence, of disease spread beyond the primary site provides information to both accurately stage and appropriately treat these patients (3–5).
Testicular cancer is often divided into two main categories: germ cell tumors and stromal tumors.
Germ cell tumors represent the vast majority of cases (90–95%) and have a good prognosis with modern therapies even at advanced stages (1,6–10).
Although the WHO proposed large changes to the classification system in 2016, germ cell tumors have historically been divided into two groups; seminoma and non-seminoma (11,12).
Stromal tumors (non-germ cell) are relatively rare, representing only 5–10% of all testicular cancer (13,14).
The five-year survival rates at early stages are still high, but for the 10–20% of patients who develop malignant disease, survival is worse than their germ cell counterparts (15–17).
Proper staging of patients has tremendous value both in prognostic and therapeutic implications.
Here, we review the role of traditional imaging modalities in detecting malignant lymph nodes in patients diagnosed with primary testicular cancer as well as its effects on staging, monitoring during active surveillance, or determining therapeutic response. This review focuses on germ cell tumors due to their greater prevalence.
Lymphatic spread
Malignant testicular cancers metastasize in a predictable fashion through the lymphatic system unless the lymphatic drainage from the testes has been altered from prior procedures.
This pattern is especially useful to the clinician when searching for positive lymph nodes.
Retroperitoneal nodes are the first landing site of metastatic disease with tumors originating from the right testicle often spreading to the inter-aortocaval lymph nodes while tumors originating in the left testicle will spread to the para-aortic lymph nodes (3,7,18,19).
Special attention should be given to the inter-aortocaval lymph nodes with a right sided primary testicular tumor as there is some evidence to suggest that more right sided positive lymph nodes are missed by radiologists than left (20).
Patients with a history of inguinal or scrotal surgery, tumor extension through the testicular capsule, or disease involving the epididymis may demonstrate positive inguinal lymph nodes due to altered lymphatic drainage (21,22).
Two types of non-seminomatous germ cell tumors (NSGCT), choriocarcinoma and yolk sac, may also rapidly metastasize hematogenously, most commonly to the lungs (3,23,24). These cases may necessitate additional imaging depending on symptomatology or clinical suspicion.
Staging
The TNMS (tumor-node-metastasis-serum markers) system from the American Joint Committee on Cancer is widely used in the staging of testicular cancers: incorporating information from pathology from the primary tumor (T stage), serum markers (S stage), and imaging to determine any lymph node or other sites of metastases (N or M stage) (4).
This information is used to appropriately counsel and treat patients with this disease (1,4,5,8).
One defining feature of early stage (less than stage II) testicular cancers is that they lack lymph node involvement.
The presence of a positive lymph node in the retroperitoneum elevates the disease to stage II, in which additional treatment is needed and active surveillance is no longer an option (4,8,10).
These cancers have penetrated local tissue, as may be seen in stage I, but additionally have spread to at least one local lymph node.
The TNMS staging system considers local lymph nodes to be located in the retroperitoneum and all others, for example supraclavicular or chest, are considered to be distant metastases (4).
The size of positive lymph nodes further stratifies stage II patients between IIA (1–5 total enlarged nodes and none are larger than 2 cm), IIB (more than 5 nodes are enlarged and/or the nodes are 2–5 cm in size) and IIC [enlarged node(s) are larger than 5 cm) (4).
Lymph node specific criteria used to stage testicular cancer are summarized in Table 1.
The 8th edition of the AJCC staging manual was implemented on January 1st, 2018.
The clinical staging of testicular cancer remained unchanged from the seventh edition, however, updates to the pathologic staging of testicular cancers was implemented.
Notably, stage I pure seminoma tumors were divided into stage T1a and T1b based on a size cutoff of 3 cm.
Additionally, epididymal, hilar soft tissue and lymphovascular invasion (LVI) of the spermatic cord without parenchymal invasion is now pT2. Lastly, discontinuous invasion of the spermatic cord and soft tissue via LVI is now considered metastatic invasion (25).
Table 1
Lymph node specific staging information
| Stage | Number of involved lymph nodes | Size of involved lymph nodes (cm) |
|---|---|---|
| I | 0 | N/A |
| II | ||
| IIA | 1–5 | <2 |
| IIB | 5+ | 2–5 |
| IIC | Any | >5 |
Evidence of disease spread to lymph nodes incorporates the number and size of affected nodes when staging testicular cancer (8).
Journal information: New England Journal of Medicine
Provided by University of California, San Francisco
