Clonal evolution in B-lineage acute lymphoblastic leukemia by contemporaneous VH-VH gene replacements and VH-DJH gene rearrangements

B-cell acute lymphoblastic leukemia (B-ALL), more frequently than any other B-lineage neoplasm, exhibits oligoclonal Ig heavy chain (IgH) gene rearrangement in 15% to 43% of all cases studied. To study the molecular processes that promote multiple IgH rearrangements, a comprehensive sequence analysis of a B-ALL case was performed in which seven clonal IgH gene rearrangements were identified. The genetic profiles suggested that a single leukemic progenitor clone evolved into several subclones through dual processes of variable (VH) to preexisting diversity-joining (DJH) gene segment rearrangement and VH to VH gene replacement. Predominant IgH-V usage and the uniquely rearranged clonotype-specific VHDJH region gene sequences were identified using a novel DNA-based gene amplification strategy. Polymerase chain reaction (PCR) was directed by an IgH-J generic primer and a complement of family-specific IgH-V primers that defined the major B-cell IgH-V gene usage. Clonality of rearranged VHDJH bands was substantiated by high resolution denaturant gel electrophoretic analysis. Sequence patterns of the amplified VHDJH fragments segregated into two groups defined by common DJH sequences. Partial N region homology at the VHD junction as well as shared DJH sequences firmly established VH to VHDJH gene replacement as a mechanism generating clonal evolution in one group. In the second subset, oligoclonality was propagated by independent VH gene rearrangements to a common DJH precursor. The contributions of all clonal Ig-VHDJH repertoires for each group was approximately 50% and reflected a symmetric distribution of leukemic subclones generated by either process. Thus, oligoclonal rearrangements evolved by two independent, yet seemingly contemporaneous molecular genetic mechanisms. All seven clones displayed nonfunctional Ig-VHDJH recombinations. These observations may have relevance to the recombinatorial opportunities available during normal B-cell maturation.     

Establishment of a human acute promyelocytic leukemia-ascites model in SCID mice

Acute promyelocytic leukemia (APL) is an interesting model for cancer research because of the presence of the specific PML-RARalpha fusion gene associated with the clinical response to retinoic acid differentiation therapy. To better understand and improve differentiation induction with retinoic acid, we have established a human APL-ascites model in SCID mice using the NB4 human APL cell line. NB4 (1 x 10(6) cells) were transplanted into the peritoneum (IP) of SCID mice for 1 month. NB4 ascites cells (A-NB4) appeared, which were then engrafted in SCID mice periodically for 18 passages at an interval of 3 to 4 weeks with a 100% success rate of tumor induction. The mean survival times of SCID mice transplanted with 1 x 10(6) A-NB4 cells was 21.6 +/- 2.3 days. Analysis of the biologic characteristics of ninth passage NB4 ascitic cells was performed and they were found to have the morphologic, immunologic, cytogenetic, and molecular features of cultured NB4 cells. Furthermore, A-NB4 cells were capable of differentiating when treated with all-trans retinoic acid (ATRA), as manifested by enhanced NBT reduction and CD11b expression. In vivo treatment with ATRA in SCID mice for 4 days also increased NBT reduction by A-NB4 cells. ATRA treatment significantly prolonged survival time in the group after transplantation (28.1 +/- 6.8 to 29.1 +/- 8.4 days) compared with the control (P < .001). Furthermore, treatment with adriamycin, an effective chemotherapeutic drug in APL, had a strong growth suppressive effect on A-NB4 cells. These results demonstrate that this SCID-APL (NB4 ascites cells) model is a useful preclinical system for evaluating new or known drugs in the treatment of APL.     

How safe is diathermy in patients with cochlear implants?

INTRODUCTION

Cochlear implants are surgically inserted electrical devices that enable severely or profoundly deaf individuals to interpret sounds from their environment and communicate more effectively. As a result of their electrical nature, they are susceptible to electromagnetic interference and can be damaged by excessive electrical energy. Surgical diathermy is one source of such potentially damaging energy. The British Cochlear Implant Group guidelines advise that monopolar diathermy should not be used in the head and neck region in patients with cochlear implants and that bipolar diathermy should not be used within 2cm of the implant (http://www.bcig.org.uk/site/public/current/safety.htm).

METHODS

A questionnaire was provided to 36 surgeons working in different specialties in the head and neck region, inquiring as to their knowledge of the safety considerations when using diathermy in cochlear implant patients. Thirty-five surgeons provided responses.

RESULTS

Overall, 77% of the respondents were unaware of the existence of published guidelines. Even when given an option to seek advice, 11% erroneously felt it was safe to use monopolar diathermy above the clavicles with a cochlear implant in situ and 49% felt that there was no restriction on the use of bipolar diathermy.

CONCLUSIONS

There is a significant deficit in the knowledge of safe operating practice in the rapidly expanding population of patients with cochlear implants which threatens patient safety. Through this publication we aim to increase awareness of these guidelines among members of the surgical community and this paper is intended to act as a point of reference to link through to the published safety guidelines.     

赛拉嗪对麻醉大鼠海马CA1区乙酰胆碱含量的影响

应用乙酰胆碱选择性微电极技术,观察到小剂量赛拉嗪(2.0和6.0mg·kg^-1)可显著增加大鼠海马CA1区ACh的含量,而大剂量赛拉嗪(10.0mg·kg^-1)及咪唑克生(0.6mg·kg^-1)则作用相反。咪唑克生虽可明显拮抗赛拉嗪的作用,但海马CA₁区ACh的含量仍显著低于正常水平。在去兰斑核的大鼠上,赛拉嗪(2.0和6.0mg·kg^-1)及咪唑克生(0.6mg·kg^-1)分别对海马CA₁区ACh的含量具有减少和增加作用,且咪唑克生拮抗赛拉嗪的作用后,海马CA₁区ACh的含量基本恢复至正常水平。结果提示,赛拉嗪对麻醉大鼠海马CA₁区ACh含量呈双相性影响,咪唑可生虽能显著拮抗赛拉嗪的作用,但海马CA₁区ACh的含量仍明显低于正常水平,可能分别与赛拉嗪和咪唑克生降低或提高中枢NE能系统的功能有关。     

Differential kinetic features by tumour topography in cutaneous small-cell neuroendocrine (Merkel cell) carcinomas

BACKGROUND/OBJECTIVES: Merkel cell carcinomas (MCC) reveal epithelial and neuroendocrine differentiation, but its topographic cell kinetics remains unknown. This study analyses proliferation, apoptosis, and DNA ploidy by topography, features that can help planning therapeutic protocols. This study topographically analyses proliferation, apoptosis, and DNA ploidy. METHODS: We selected 27 small-cell MCCs (expressing one epithelial and two neural markers, with consistent ultrastructural findings) to evaluate mitotic figure counting, Ki-67 index, apoptosis index based on the in situ end labelling of fragmented DNA (using Escherichia coli DNA polymerase I, Klenow fragment), DNA ploidy, and BCL2 and TP53 immuno-expression. At least 50 high-power fields were screened per topographic compartment (superficial or papillary dermis, and deep or reticular dermis), recording average and standard deviation for each variable. Variables were statistically compared in each tumour compartment using analysis of variance and Student's t-test (significant if P < 0.05). RESULTS: MCCs revealed superficial aneuploid DNA content, and no topographic differences for proliferation markers. Apoptosis showed significantly lower values in the deep compartment (average, P = 0.0050, and standard deviation, P = 0.0074), correlating with increased BCL2 and TP53 immuno-expressions. CONCLUSIONS: High homogeneously distributed proliferation and superficial aneuploid DNA content defines MCCs. Apoptosis follows proliferation in superficial compartments, being less variable and proliferation independent in deep compartments, where it is inversely correlated with BCL2/TP53 expression.