Gastrointestinal beta2microglobulin amyloidosis in hemodialysis patients: biochemical analysis of amyloid proteins in small formalin-fixed paraffin-embedded tissue specimens

Diagnostic Challenges and Solutions in Systemic Amyloidosis

Amyloidosis refers to a clinically heterogeneous group of disorders characterized by the extracellular deposition of amyloid proteins in various tissues of the body. To date, 42 different amyloid proteins that originate from normal precursor proteins and are associated with distinct clinical forms of amyloidosis have been described. Identification of the amyloid type is essential in clinical practice, since prognosis and treatment regimens both vary according to the particular amyloid disease. However, typing of amyloid protein is often challenging, especially in the two most common forms of amyloidosis, i.e., the immunoglobulin light chain amyloidosis and transthyretin amyloidosis. Diagnostic methodology is based on tissue examinations as well as on noninvasive techniques including serological and imaging studies. Tissue examinations vary depending on the tissue preparation mode, i.e., whether it is fresh-frozen or fixed, and they can be carried out by ample methodologies including immunohistochemistry, immunofluorescence, immunoelectron microscopy, Western blotting, and proteomic analysis. In this review, we summarize current methodological approaches used for the diagnosis of amyloidosis and discusses their utility, advantages, and limitations. Special attention is paid to the simplicity of the procedures and their availability in clinical diagnostic laboratories. Finally, we describe new methods recently developed by our team to overcome limitations existing in the standard assays used in common practice.

An Organ System-Based Approach to Differential Diagnosis of Amyloid Type in Surgical Pathology

CONTEXT.—

Amyloidosis is an uncommon but important entity. A protein-based classification of amyloidosis defines the underlying disease process, directing clinical management and providing prognostic information. However, in routine surgical pathology there often is no attempt to classify amyloid other than staining to determine light chain-associated amyloidosis. Systemic and localized amyloidosis vary with respect to frequency of organ involvement by different amyloid types, and most amyloid proteins have commercial antibodies available for identification.

OBJECTIVE.—

To provide a guide for the likelihood of amyloid type by organ system.

DATA SOURCES.—

Literature review based on PubMed searches containing the word amyloid, specifically addressing the prevalence and significance of amyloid proteins in each organ system other than the brain, and the authors' practice experience.

CONCLUSIONS.—

In patients with amyloidosis, determination of the responsible protein is critical for appropriate patient care. In large subspecialty practices and reference laboratories with experience in using and analyzing relevant immunohistochemistry, most amyloid proteins can be identified with an organ-specific algorithm. Referring to an organ-based algorithm may be helpful in providing clinicians with a more specific differential diagnosis regarding amyloid type to help guide clinical evaluation and treatment. When the protein cannot be characterized, mass spectrometry can be performed to definitively classify the amyloid type.

ATP5b and β2-microglobulin are predictive markers for the prognosis of patients with gallbladder cancer

The differences in clinical, pathological, and biological characteristics between adenocarcinoma (AC) and squamous cell/adenosquamous carcinoma (SC/ASC) of the gallbladder have not been well documented. This study investigates the clinical and pathological associations of ATP5B and β2M with benign and malignant lesions of the gallbladder. In this study, ATP5B and β2M expression in 46 SC/ASCs and 80 ACs were examined using immunohistochemistry. The rate of ATP5B positive expression was significantly lower, while the rate of β2M expression was significantly higher, in AC and SC/ASC than in gallbladder adenomas, gallbladder polyps, or gallbladder epithelium with stone (P < 0.01). More SC/ASCs had larger tumor mass and good differentiation compared to ACs. Positive β2M and negative ATP5B expression were significantly associated with large tumor size, high TNM stage, lymph node metastasis, and invasion of SC/ASCs and ACs. Univariate Kaplan-Meier analysis showed that positive β2M (P < 0.05 or P < 0.001) expression and negative ATP5B (P < 0.001) expression were significantly associated with decreased overall survival in both SC/ASC and AC patients. Multivariate Cox regression analysis showed that negative ATP5B expression is an independent-prognostic factor for poor prognosis in both SC/ASC (P < 0.01) and AC (P < 0.001) patients. Positive β2M expression is an independent-prognostic factor for poor prognosis in AC (P < 0.05) patients. Our study suggested that positive β2M expression or loss of ATP5B expression in tumor tissues is closely related to the metastasis, invasion, and poor-prognosis of gallbladder cancer.

Upregulation of β2-microglobulin expression in progressive human oral squamous cell carcinoma

The aim of the present study was to investigate β2-microglobulin (β2-M) expression in normal oral mucosa and progressive oral squamous cell carcinoma (OSCC) and to assess the clinical significance of β2-microglobulin expression. The study included 10 cases of normal oral mucosa epithelium specimens, 55 cases of primary OSCC specimens, and 25 cases of OSCC metastasis specimens. Immunohistochemistry was used to determine β2-M expression, and its correlation with clinicopathological factors in progressive OSCC was evaluated. Immunohistochemistry showed that strong β2-M expression was significantly asscociated with tumor size (T3, T4 vs. T1, T2; P=0.001), positive node status (N positive vs. N negative; P=0.000) and advanced clinical stage (III, IV vs. I, II, P=0.000) in primary OSCC lesions. Compared to primary OSCC lesions, the frequency of β2-M expression was significantly increased in metastatic OSCC lesions (P=0.02). In addition, in vitro results from Western blotting showed increased β2-M expression in the two OSCC lines studied. Therefore, we speculate that the up-regulation of β2-M expression may contribute to the oncogenesis of human oral mucosa, tumor invasion and metastasis.

Charge differences between in vivo deposits in immunoglobulin light chain amyloidosis and non-amyloid light chain deposition disease

Immunoglobulin light chain amyloidosis (AL) and non-amyloid light chain deposition disease (NALCDD) are different forms of protein aggregation disorders that may occur in plasma cell dyscrasias with dysproteinemia. In systemic AL, the deposits are fibrillar and patchy in distribution, within and amongst different organs, whereas in NALCDD, the deposits are granular and diffusely distributed in systemic basement membranes, suggesting different mechanisms of aggregation and deposition. Previous evidence, that charge differences between the light chains in AL and NALCDD might account for their different phenotypes, prompted the present study, which compared the isoelectric points (pIs) of AL and NALCDD protein deposits extracted from human tissues. The pI profiles (5.2-8.8) of polypeptides in AL deposits were heterogenous in four cases, with a spread of both anionic and cationic isoforms; in contrast, in three of NALCDD the pI profiles (8.2-8.8) were homogeneous and restricted in the cationic range. These in vivo findings in human disease, together with other reported in vitro and in vivo experimental data, suggest that the fibrillar deposits in AL may form by electrostatic interaction between oppositely charged polypeptides, whereas the granular deposits in NALCDD form by the binding of cationic polypeptides to anionic proteoglycans sites in basement membranes.

Transthyretin amyloidosis in a patient of Iranian-Jewish extraction: a second Israeli-Jewish case

BACKGROUND

We present a patient with late-onset progressive polyneuropathy and a Congo-red positive staining of sural nerve biopsy, where routine immunohistochemical analysis failed to determine the type of amyloid deposited. Since precise determination of the amyloid type has crucial therapeutic implications, we employed our new biochemical micro-techniques, together with molecular biology methods, to characterize the amyloid protein deposited.

METHODS

We used a micro-method for extraction of amyloid proteins, amyloid typing by Western blotting, DNA sequencing, and restriction enzyme site analysis.

RESULTS

Our new micro-technique for biochemical analysis of fat aspirate demonstrated transthyretin (TTR) amyloid (ATTR) deposition in the patient's tissue. Sequence analysis of the TTR-encoding DNA identified a single mutation, causing a valine to alanine substitution (V32A).

CONCLUSIONS

Although there are approximately 100 known TTR variants associated with peripheral neuropathy, in Israel only one patient with familial amyloid polyneuropathy (FAP), a patient of Ashkenazi origin with ATTR due to an F33I mutation, has been reported so far. Our study identified a second case of ATTR in the Israeli population, this time in a patient of Iranian-Jewish extraction. The study also emphasizes the importance of our new biochemical micro-techniques in elucidating the type of amyloid protein.