Contributions of recent research to the classification of spontaneous lymphoid cell neoplasms in mice

B-cell lymphoblastic lymphoma following intravenous BNT162b2 mRNA booster in a BALB/c mouse: A case report

Unprecedented immunization campaigns have been rolled out worldwide in an attempt to contain the ongoing COVID-19 pandemic. Multiple vaccines were brought to the market, among two utilizing novel messenger ribonucleic acid technology. Despite their undisputed success in decreasing COVID-19-associated hospitalizations and mortality, various adverse events have been reported. The emergence of malignant lymphoma is one of such rare adverse events that has raised concern, although an understanding of the mechanisms potentially involved remains lacking. Herein, we present the first case of B-cell lymphoblastic lymphoma following intravenous high-dose mRNA COVID-19 vaccination (BNT162b2) in a BALB/c mouse. Two days following booster vaccination (i.e., 16 days after prime), at only 14 weeks of age, our animal suffered spontaneous death with marked organomegaly and diffuse malignant infiltration of multiple extranodal organs (heart, lung, liver, kidney, spleen) by lymphoid neoplasm. Immunohistochemical examination revealed organ sections positive for CD19, terminal deoxynucleotidyl transferase, and c-MYC, compatible with a B-cell lymphoblastic lymphoma immunophenotype. Our murine case adds to previous clinical reports on malignant lymphoma development following novel mRNA COVID-19 vaccination, although a demonstration of direct causality remains difficult. Extra vigilance is required, with conscientious reporting of similar cases and a further investigation of the mechanisms of action explaining the aforementioned association.

Phenotyping analysis of p53 knockout mice produced by gene editing and comparison with conventional p53 knockout mice

BACKGROUND

Knockout (KO) mice developed by homologous recombination (HR) have become useful tools to elucidate gene function. However, HR has low KO efficiency and is time-consuming, labor-intensive, and expensive. 'Gene editing' has received much attention for efficient genetic manipulation.

OBJECTIVE

As generation of KO mice is simplified, KO mice produced by HR can be feasibly reproduced using gene editing. However, phenotyping analysis and comparison between KO mice produced by these two techniques is necessary.

METHODS

We generated p53 KO mice through gene editing and compared their phenotype with the already reported HR-mediated p53 KO mice.

RESULTS

Tumors occurred in 36 (73%) of 49 homozygous KO mice and the mean age of occurrence was 23 weeks, with lymphoma (64%) and sarcoma (23%) being the most common. Tumors were also developed in 12 heterozygous mice and the mean age of occurrence was 40 weeks, with sarcoma (54%) and lymphoma (46%) in high proportion. Homozygotes had a mean life span of 157 ± 52 days and developmental abnormalities were found in females compared to in males (P < 0.05, P < 0.001).

CONCLUSION

We analyzed the basic phenotype of p53 KO mice and observed no significant difference from the conventional HR-mediated p53 KO mice.

Disruption of the ARF transcriptional activator DMP1 facilitates cell immortalization, Ras transformation, and tumorigenesis

The DMP1 transcription factor induces the ARF tumor suppressor gene in mouse fibroblasts, leading to cell cycle arrest in a p53-dependent manner. We disrupted sequences encoding the DNA-binding domain of DMP1 in mouse embryonic stem cells and derived animals lacking the functional protein. DMP1-null animals are small at birth, and males develop more slowly than their wild-type littermates. Some adult animals exhibit seizures and/or obstuctive uropathy, each of unknown cause. The growth of explantedDMP1-null mouse embryo fibroblasts (MEFs) is progressively retarded as cells are passaged in culture on defined transfer protocols; but, unlike the behavior of normal cells, p19ARF, Mdm2, and p53 levels remain relatively low and DMP1-null MEFs do not senesce. Whereas the establishment of cell lines from MEFs is usually always accompanied by either p53 or ARF loss of function, continuously passaged DMP1-null cells readily give rise to established 3T3 and 3T9 cell lines that retain wild-type ARFand functional p53 genes. Early-passage DMP1-null cells, like MEFs from either ARF-null or p53-null mice, can be morphologically transformed by oncogenic Ha-Ras (Val-12) alone. Splenic lymphocytes harvested from both DMP1-null andARF-null mice exhibit enhanced proliferative responses in long-term cultures when stimulated to divide with antibody to CD3 and interleukin-2. Although only 1 of 40 DMP1-null animals spontaneously developed a tumor in the first year of life, neonatal treatment with dimethylbenzanthracene or ionizing radiation induced tumors of various histologic types that were not observed in similarly treated DMP1+/+ animals. Karyotypic analyses of MEFs and lymphomas from DMP1-null animals revealed pseudodiploid chromosome numbers, consistent with the retention of wild-type p53. Together, these data suggest that ARF function is compromised, but not eliminated, in animals lacking functional DMP1.

Expression of the Human Immunodeficiency Virus-Tat Gene in Lymphoid Tissues of Transgenic Mice Is Associated With B-Cell Lymphoma

The human immunodeficiency virus type 1 (HIV-1) Tat gene, a potent transactivator of viral and cellular genes, has been proposed as a key agent in the pathogenesis of acquired immune deficiency syndrome related disorders, including nonHodgkin’s lymphoma. In cultured cells, the HIV-1 Tat protein can induce the expression of the cytokines interleukin-6 (IL-6) and IL-10, which are known to induce proliferation and differentiation of lymphoid cells. Such alterations in cytokine expression, together with a secondary genetic event, are thought to ultimately lead to oncogenic transformation. To address the influence of Tat on lymphoid development in the context of the whole organism, we produced several transgenic mouse lines that express the Tat gene under the control of an actin promoter. We show here that this promoter directs expression to a variety of sites, including spleen, bone marrow, and lymph nodes. Approximately 25% to 30% of the Tat-transgenic population developed enlarged spleens within 1 year after birth. On histological examination, a significant number of spleens from Tat-transgenic mice exhibited malignant lymphoma of B-cell origin. IgG heavy chain rearrangement confirmed the clonal B-cell nature of these lymphoproliferations. In contrast, T-cell receptor genes exhibited a germline (unrearranged) structure. Reverse transcription polymerase chain reaction analysis of transgenic spleens revealed that mRNA encoding cytokines IL-6 and IL-10 was upregulated, suggesting a possible mechanism for the B-cell expansion in vivo.

Attendance at religious services, interleukin-6, and other biological parameters of immune function in older adults

OBJECTIVE

First, to examine and explain the relationship between religious service attendance and plasma Interleukin-6 (IL-6) levels, and second, to examine the relationship between religious attendance and other immune-system regulators and inflammatory substances.

METHODS

During the third in-person interview (1992) of the Establishment of Populations for Epidemiologic Studies of the Elderly (EPESE) project, Duke site, 1718 subjects age sixty-five or over had blood drawn for analysis of immune regulators and inflammatory factors, including IL-6 measurements. IL-6 was examined both as a continuous variable and at a cutoff of 5 pg/ml. Information on attendance at religious services was available from the 1992 interview and two prior interviews (1986 and 1989).

RESULTS

Religious attendance was inversely related to high IL-6 levels (> 5 pg/ml), but not to IL-6 measured as a continuous variable. Bivariate analyses revealed that high religious attendance in 1989 predicted a lower proportion of subjects with high IL-6 in 1992 (beta-.10, p = .01) High religious attendance in 1992 also predicted a lower proportion of subjects with high IL-6 levels in 1992 (beta-.14, p = .0005). When age, sex, race, education, chronic illnesses, and physical functioning were controlled, 1989 religious attendance weakened as a predictor of high IL-6 (beta-.07, p = .10), but 1992 religious attendance retained its effect (beta-.10, p = .02). When religious attenders were compared to non- attenders, they were only about one-half as likely to have IL-6 levels greater than 5 ng/ml (OR 0.58, 95% CI 0.40-0.84, p < .005). Religious attendance was also related to lower levels of the immune-inflammatory markers alpha-2 globulin, fibrin d-dimers, polymorphonuclear leukocytes, and lymphocytes. While controlling for covariates weakened most of these relationships, adjusting analyses for depression and negative life events had little effect.

CONCLUSIONS

There is a weak relationship between religious attendance and high IL-6 levels that could not be explained by other covariates, depression, or negative life events. This finding provides some support for the hypothesis that older adults who frequently attend religious services have healthier immune systems, although mechanism of effect remains unknown.

Lymphoma induced in mice chronically exposed to very strong low-frequency electromagnetic field

Three successive generations of CFW mice were exposed to a 25-mT (250,000 mG), 60-Hz electromagnetic field for prolonged periods. At the end of the exposure period, animals from both the exposed and control groups were sacrificed for tests. A complete autopsy was performed and tissue sections were taken from the main organs for histopathological examination. The results from the pathological findings in the various animals were classified under the following categories: (1) normal; (2) lymphoid hyperplasia; (3) premalignant changes; (4) early lymphoma; (5) advanced lymphoma. The three first-generation animals developed generalized lymphoid hyperplasia. In the second-generation animals, 5% developed premalignant changes, and 15.8% had lymphoid hyperplasia. In addition, 4 female mice left in the field for 418 days developed malignant lymphoma. In the third-generation animals, 58% developed premalignant changes or malignant lymphoma. An additional 30% had lymphoid hyperplasia. Statistical analysis of the data using the Mantel-Haenszel test for the difference in the prevalence of lymphoma between the exposed and control groups shows a very significant difference for the male groups (P < 0.001), the female groups (P < 0.001), and all animals combined (P < 0.001). The results suggest a cause-effect relationship between chronic exposure to very strong 60-Hz magnetic field for prolonged period and the development of malignant lymphoma in CFW mice.

Carcinogenicity of policosanol in mice: an 18-month study

Policosanol (trade name Ateromixol) is a new cholesterol-lowering drug that has been isolated and purified from sugar cane wax. The effects of policosanol (50-500 mg/kg) administered orally for 18 months to male and female Swiss mice were investigated. No differences in daily clinical observations, weight gain, food consumption and mortality (survival analysis) between groups were found. Histopathological study showed that the frequency of neoplastic (benign and malignant) lesions was similar in the control and policosanol-treated groups. The lesions observed were similar to the spontaneous lesions in Swiss mice reported in previous studies. As no drug-related increase in the occurrence of malignant or benign neoplasm was found, nor acceleration in tumour growth in any specific group observed, this study shows no evidence of policosanol-induced carcinogenicity in Swiss mice.

The role of interleukin-6 in certain age-related diseases

Interleukin-6 (IL-6) is a pro-inflammatory cytokine with a wide range of functions. Perhaps the most important physiologically is its role as a mediator of the acute phase inflammatory response. Normally, there is little measurable IL-6 in the circulation, but levels increase abruptly to nanogram amounts during an inflammatory process. During aging, it has been proposed that the tight regulation of IL-6 gene expression becomes less effective and levels are measurable even when there is no evidence for inflammation. Several investigators have identified this cytokine as being involved in the pathogenesis of various disease processes and we have suggested that certain age-associated diseases are directly related. Among these are late-life lymphoma and myeloma, osteoporosis and possibly Alzheimer's disease.

Expression of mononuclear phagocyte antigens in histiocytic sarcoma of mice

Twenty cases of histiocytic sarcoma in 15 female and five male (384 to 722 days of age) hybrid F1 (C57BL/6 x BALB/c) or F2 (F1 x F1) mice were studied for expression of mononuclear phagocyte and other antigens. Histiocytic sarcomas were found most often in liver, uterus, spleen, and lung. Tissues fixed in Bouin's fluid provided preservation of antigen immunoreactivity, using avidin biotin peroxidase complex immunohistochemistry, with monoclonal and polyclonal antibodies. The mononuclear phagocyte antigens, lysozyme and Mac-2 (a galactose-specific lectin that binds IgE), were found in 60-70% of the cases. The receptor for the macrophage colony-stimulating factor (CSF-1), c-fms, was expressed in 2/20 (10%) of the cases. Mouse immunoglobulins were not found in histiocytic sarcoma cells. In uterine histiocytic sarcomas, previously reported as Schwannomas because of their histologic appearance, S-100 protein was not expressed by tumor cells, although they usually expressed Mac-2 and lysozyme. Hyaline droplets were found in the renal tubules of only 2/19 cases. Our studies provide evidence that murine histiocytic sarcoma expresses antigens (Mac-2, lysozyme, c-fms) found in cells of the mononuclear phagocyte series, in contrast to the B-cell origin of many human histiocytic tumors.

The morphology, immunohistochemistry, and incidence of hematopoietic neoplasms in mice and rats

Hematopoietic neoplasms in the rodent may be classified into lymphoid or nonlymphoid neoplasms. Lymphoid neoplasms include the following morphologic types: follicular center cell, lymphoblast (lymphocytic), immunoblast, plasma cell, and large granular lymphocyte (LGL). Nonlymphoid hematopoietic neoplasms include histiocytic sarcoma, granulocytic leukemia, erythroid leukemia, and mast cell tumors. Most types of hematopoietic neoplasms, exclusive of LGL lymphoma (leukemia), are more common in mice than in rats. Specific strains of mice have a hematopoietic tumor incidence of more than 50% in aged animals. Some strains of rats (i.e., Fischer-344) may have an incidence of over 50% of LGL lymphoma in aged animals. The tumor type and incidence are characteristic for each rat or mouse strain. Hematopoietic neoplasms have been better characterized immunomorphologically in mice than in rats. The specific cell type and tissue of origin for hematopoietic neoplasms may be important for safety evaluation of chemicals. Specific chemicals may induce specific types of these tumors, which may be the same or different from the spontaneous types. Lymphoid cell neoplasms should not be grouped with nonlymphoid neoplasms in determining the toxicity and carcinogenicity of test substances.

Interleukin-6: a cytokine for gerontologists

Interleukin-6 (IL-6) is a multifunctional cytokine that presumably plays its major role as a mediator of several of the acute phase inflammatory responses. These include inflammatory cell and lymphocyte activation and hepatocellular stimulation of acute phase protein synthesis. IL-6 expression is normally low, and serum levels are usually non-detectable in the absence of inflammation. However, with advancing age, serum levels become detectable, and it is proposed that this reflects an age-associated loss in the normal regulation of gene expression for this molecule. The cause of this is most likely multi-factorial, but there is evidence that it relates to an age-associated loss of T cell immunoregulatory functions as well as menopausal loss of estrogen. In any event, the "inappropriate" presence of IL-6 results in many changes typical of chronic inflammation. There is also speculation that IL-6 may contribute to the pathogenesis of several diseases of late-life including lymphoma, osteoporosis, and Alzheimer's disease. In this review the biology of this important cytokine is presented and its relevance to gerontology is highlighted.

Spontaneous follicular center cell lymphomas of B cell origin in cataract mice

Spontaneous lymphomas from a strain of hereditary cataract (CAC-nct/+) mice were examined by light and electron microscopy and by immunohistochemical reaction for the mouse heavy and light immunoglobulin chains. Lymphomas occurred in 28 out of 45 male cataract mice and in 34 out of 52 females at 25 to 65 weeks of age. All of the lymphoma-bearing mice showed an enlargement of the spleen and mesenteric lymph nodes, and some mice also had hepatomegaly. Morphologically, all tumors were composed of a mixed population of small and large cells. Neoplastic cells had features of follicular center cell lymphomas, such as scant to moderate amounts of cytoplasm and cleaved and/or round nuclei with a large nuclear-to-cytoplasmic ratio. Large cells were often admixed with small cells, and had vesicular nuclei with prominent nucleoli juxtaposed to the nuclear membrane. Intracytoplasmic eosinophilic inclusions were observed in occasional cells, but Golgi apparatus was poorly developed and rough-surfaced endoplasmic reticulum was scant, unlike those in plasma cells. C-particles were seen in all lymphoma-bearing mice by electron microscopy. Intracisternal A-particles were detected in some mice. Immunohistochemically, neoplastic lymphoid cells were positive for the kappa light chain and the surface/cytoplasmic immunoglobulin M. These results indicate that lymphoid cell neoplasms found in hereditary cataract mice originate from follicular center B cells.

An immunohistochemical study of spontaneous lymphomas in the C57B1/10J mouse

Immunocytochemistry was used to examine 26 cases of composite lymphoma in the mouse mesenteric lymph node. The diagnosis was made by light microscopic criteria. A selection of polyclonal antibodies to light (Kappa and Lambda) and heavy chain (IgD, IgM, IgC, IgA, IgE) antigens was used together with three monoclonal antibodies to T cells, B cells (HLA-DR) and macrophages. Twenty lymphomas were classified as B cell and six as T cell. The B cells were subdivided into IgM and IgD (five), IgD (five), IgM (three) and IgA (one), three undifferentiated and, in three, there was insufficient tissue for further typing. There did not appear to be any correlation between the morphological appearance and the immunophenotype.

Hyaline droplet accumulation in rodent kidney proximal tubules: an association with histiocytic sarcoma

Since recognition during the last decade that certain renal carcinogens can initially cause an accumulation of hyaline (protein) droplets in proximal tubules of male rats, it has become appropriate to establish whether this phenomenon of protein overload can also occur in rodent kidneys unrelated to chemical treatment. Kidney tissue from a number of selected rodent studies held in the National Toxicology Program (NTP) or Food and Drug Administration (FDA) archives were evaluated for hyaline droplet accumulation in proximal tubules. The survey concentrated on rats and mice of both sexes bearing hematopoietic tumors, as our preliminary observations had suggested this direction of study. The tissues of 101 Sprague-Dawley, 25 Osborne-Mendel, and 70 Fischer 344 rats and 96 B6C3F1 mice were examined. These animals provided an assortment of tumors including histiocytic sarcoma, lymphocytic lymphoma, mononuclear cell leukemia, and sarcoma. Hyaline droplet accumulation, primarily involving the P2 segment of proximal tubules, was diagnosed in 96% of rats with histiocytic sarcoma (74/77 cases in Sprague-Dawley, 17/18 in Osborne-Mendels, 7/7 in Fischers) and in 55% of B6C3F1 mice with histiocytic sarcoma (18/33 cases). There appeared to be a qualitative correlation between hyaline droplet accumulation and degree of tumor burden. Thus, in cases negative for hyaline droplets, the tumor was often confined to a single location, while increasing involvement of proximal segments beyond P2 occurred with more extensive multi-organ dissemination of the tumor. By immunohistochemistry on 11 cases of rat and 8 cases of mouse histiocytic sarcoma, the protein in hyaline droplets was identified as lysozyme, a known major secretory product of monocytes and macrophages. The hyaline droplets were negative for alpha 1-antitrypsin, alpha 2u-globulin, rat or mouse immunoglobulin, and albumin. More sparsely scattered droplets and granules present in proximal tubules of Fischer rats with mononuclear cell leukemia were negative for lysozyme but positive for either iron or lipofuscin pigment. The study establishes a clear association between renal tubule hyaline droplet and lysozyme accumulation in rats and mice with histiocytic sarcoma. Hyaline droplets secondary to neoplasia should be distinguished from chemically-induced hyaline droplet nephropathy in the male rat involving alpha 2u-globulin.

Applications of immunohistochemistry in rodent tumor pathology

Immunohistochemistry can serve as a valuable adjunct to rodent tumor pathology. Specific antigens may be localized to cells and tissues in normal organs, preneoplastic lesions, and benign and malignant tumors. The immunoreactivity of polyclonal and monoclonal antibodies to these antigens provide a more accurate basis for tumor diagnosis and aid in understanding pathogenesis. Ultimately, the application of more precise understanding of tumor histogenesis and diagnosis will lead to more accurate interpretations of tumor incidence data for safety assessment in toxicology.

Chronic toxicity of sodium nitrite in the male F344 rat

A long-term feeding study was carried out in rats with sodium nitrite. The test substance was administered as part of a reduced-protein diet to groups of 50, 6-wk-old, male F344 rats at dose levels of 0.2 or 0.5% (w/w) sodium nitrite for up to 115 wk. A control group of 20 males received the reduced-protein diet alone. Throughout the study, there was a dose-related decrease in the rates of body-weight gains and a corresponding decrease in body weights among animals fed sodium nitrite in the diet. Food intakes of rats in the low-dose group were slightly raised over most of the study. In the high-dose group, food intakes were reduced during the first month, but thereafter were similar to those of the control group. This reduction in food intake together with the lower body weights in the nitrite-treated animals, may indicate a reduction in food utilization. In the first week of treatment the following haematological parameters were reduced: red blood cell count, haematocrit and haemoglobin concentration. The red blood cell count continued to fall for 8 wk, then slowly returned to normal by wk 52. A dose-related reduction was noted in both the incidence and time of onset of lymphomas, leukaemias and testicular interstitial cell tumours. Leukaemias were only found in animals with lymphoma, indicating an association between the two lesions. Under the conditions described in this study, sodium nitrite was found not to be carcinogenic when fed to rats in the diet for up to 115 wk, but rather that the incidence of tumours was reduced in a dose-related manner, which correlated with a similar trend in body weights.

Morphologic classification and incidence of hematopoietic neoplasms in the Sprague-Dawley rat

Hematopoietic and related neoplasms were morphologically studied in a total of 1,765 male and 1,765 female Sprague-Dawley rats from 6 chronic toxicity studies conducted at a large toxicology testing laboratory. The most common types of lymphoid neoplasms seen included the lymphoblastic lymphoma (0.65%) and the large granular lymphocyte lymphoma (LGL, Fischer or mononuclear cell leukemia) (0.60%). The most common type of nonlymphoid neoplasm with morphologic features similar to lymphoid tumors was histiocytic sarcoma (1.1%). A small number of cases of myelogenous leukemia were also seen. Additional work is needed in the classification of hematopoietic neoplasms in rats including refined immunomorphological studies.