Identification of the catalytic subunit of DNA dependent protein kinase as the product of the mouse scid gene

Establishment of Nude Mice Lacking NK Cells and Their Application for Human Tumor Xenografts

OBJECTIVE

Nude mice are used as a recipient for human tumor cell xenografts. However, the success rate of xenotransplantation is unsatisfactory due to high natural killer (NK) activity. To overcome this limitation, we established nude mice with no NK cells, and compared the transplantation efficiency with that in nude mice.

METHODS

BALB/c Nude Jak3-/- (Nude-J) mice were established by crossing BALB/c Nude mice and BALB/c Jak-3-/- mice. Hematopoietic malignant cell lines (BCBL-1 and Z138) were implanted subcutaneously to compare the tumorigenicity in Nude-J mice with Nude Rag-2/Jak3 double deficient (Nude RJ) mice and nude mice.

RESULTS

Nude-J mice showed complete loss of NK and T lymphocytes, whereas B lymphocytes remained. Both BCBL-1 and Z138 human lymphoid malignant cell lines formed almost the same sizes of subcutaneous tumors in Nude-J and Nude RJ mice, whereas they formed no or only small tumors in nude mice. Splenocytes from Nude-J mice showed no cytotoxic activity in vitro.

CONCLUSION

Nude-J mice can be a valuable tool for human tumor cell transplantation studies.
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Humanized mouse models of genetic immune disorders and hematological malignancies

The immune system is quite remarkable having both the ability to tolerate innocuous and self-antigens while possessing a robust capacity to recognize and eradicate infectious pathogens and foreign entities. The genetics that encode this delicate balancing act include multiple genes and specialized cell types. Over the past several years, whole exome and whole genome sequencing has uncovered the genetics driving many human immune-mediated diseases including monogenic disorders and hematological malignancies. With the advent of genome editing technologies, the ability to correct genetic immune defects in autologous cells holds great promise for a number of conditions. Since assessment of novel therapeutic strategies have been difficult in mice, in recent years, immunodeficient mice capable of engrafting human cells and tissue have been developed and utilized for a variety of research applications. In this review, we discuss immune-humanized mice as a research tool to study human immunobiology and genetic immune disorders in vivo and the promise of future applications.

The DNA-dependent protein kinase: A multifunctional protein kinase with roles in DNA double strand break repair and mitosis

The DNA-dependent protein kinase (DNA-PK) is a serine/threonine protein kinase composed of a large catalytic subunit (DNA-PKcs) and the Ku70/80 heterodimer. Over the past two decades, significant progress has been made in elucidating the role of DNA-PK in non-homologous end joining (NHEJ), the major pathway for repair of ionizing radiation-induced DNA double strand breaks in human cells and recently, additional roles for DNA-PK have been reported. In this review, we will describe the biochemistry, structure and function of DNA-PK, its roles in DNA double strand break repair and its newly described roles in mitosis and other cellular processes.

Regulation of DNA metabolic enzymes upon induction of preB cell development and V(D)J recombination: up-regulation of DNA polymerase delta

Withdrawal of interleukin-7 from cultured murine preB lymphocytes induces cell differentiation including V(D)J immunoglobulin gene rearrangements and cell cycle arrest. Advanced steps of the V(D)J recombination reaction involve processing of coding ends by several largely unidentified DNA metabolic enzymes. We have analyzed expression and activity of DNA polymerases alpha, beta, delta and epsilon, proliferating cell nuclear antigen (PCNA), topoisomerases I and II, terminal deoxynucleotidyl transferase (TdT) and DNA ligases I, III and IV upon induction of preB cell differentiation. Despite the immediate arrest of cell proliferation, DNA polymerase delta protein levels remained unchanged for approximately 2 days and its activity was up-regulated several-fold, while PCNA was continuously present. Activity of DNA polymerases alpha,beta and epsilon decreased. Expression and activity of DNA ligase I were drastically reduced, while those of DNA ligases III and IV remained virtually constant. No changes in DNA topoisomerases I or II expression and activity occurred and TdT expression was moderately increased early after induction. Our results render DNA polymerase delta a likely candidate acting in DNA synthesis related to V(D)J recombination in lymphocytes.