The Postoperative Breast: Imaging Findings and Diagnostic Pitfalls After Breast-Conserving Surgery and Oncoplastic Breast Surgery

Breast surgery is the cornerstone of treatment for early breast cancer. Historically, mastectomy and conventional breast-conserving surgery (BCS) were the main surgical techniques for treatment. Now, oncoplastic breast surgery (OBS), introduced in the 1990s, allows for a combination of BCS and reconstructive surgery to excise the cancer while preserving or enhancing the contour of the breast, leading to improved aesthetic results. Although imaging after conventional lumpectomy demonstrates typical postsurgical changes with known evolution patterns over time, OBS procedures show postsurgical changes/fat necrosis in locations other than the lumpectomy site. The purpose of this article is to familiarize radiologists with various types of surgical techniques for removal of breast cancer and to distinguish benign postoperative imaging findings from suspicious findings that warrant further work-up.

The ACR Learning Network: Facilitating Local Performance Improvement Through Shared Learning

PURPOSE

The ACR Learning Network was established to test the viability of the learning network model in radiology. In this report, the authors review the learning network concept, introduce the ACR Learning Network and its components, and report progress to date and plans for the future.

METHODS

Patterned after institutional programs developed by the principal investigator, the ACR Learning Network was composed of four distinct improvement collaboratives. Initial participating sites were solicited through broad program advertisement. Candidate programs were selected on the basis of assessments of local leadership support, experience with quality improvement initiatives, intraorganizational relationships, and access to data and analytic support. Participation began with completing a 27-week formal quality improvement training and project support program, with local teams reporting weekly progress on a common performance measure.

RESULTS

Four improvement collaborative topics were chosen for the initial cohort with the following numbers of participating sites: mammography positioning (6), prostate MR image quality (6), lung cancer screening (6), and follow-up on recommendations for management of incidental findings (4). To date, all sites have remained actively engaged and have progressed in an expected fashion. A detailed report of the results of the improvement phase will be provided in a future publication.

CONCLUSIONS

To date, the ACR Learning Network has successfully achieved planned milestones outlined in the program's plan, with preparation under way for the second and third cohorts. By providing a shared platform for improvement training and knowledge sharing, the authors are optimistic that the network may facilitate widespread performance improvement in radiology on a number of topics for years to come.

Breast Density Legislation Impact on Breast Cancer Screening and Risk Assessment

OBJECTIVE

To evaluate breast density notification legislation (BDNL) on breast imaging practice patterns, risk assessment, and supplemental screening.

METHODS

A 20-question anonymous web-based survey was administered to practicing Society of Breast Imaging radiologists in the U.S. between February and April 2021 regarding breast cancer risk assessment, supplemental screening, and density measurements. Results were compared between facilities with and without BDNL using the two-sided Fisher's exact test.

RESULTS

One hundred and ninety-seven radiologists from 41 U.S. states, with (187/197, 95%) or without (10/197, 5%) BDNL, responded. Fifty-seven percent (113/197) performed breast cancer risk assessment, and 93% (183/197) offered supplemental screening for women with dense breasts. Between facilities with or without BDNL, there was no significant difference in whether risk assessment was (P = 0.19) or was not performed (P = 0.20). There was no significant difference in supplemental screening types (P > 0.05) between BDNL and non-BDNL facilities. Thirty-five percent (69/197) of facilities offered no supplemental screening studies, and 25% (49/197) had no future plans to offer supplemental screening. A statistically significant greater proportion of non-BDNL facilities offered no supplemental screening (P < 0.03) and had no plans to offer supplemental screening compared to BDNL facilities (P < 0.02).

CONCLUSION

Facilities in BDNL states often offer supplemental screening compared to facilities in non-BDNL states. Compared to BDNL facilities, a statistically significant proportion of non-BDNL facilities had no supplemental screening nor plans for implementation. Our data suggest that upcoming federal BDNL will impact how supplemental screening is addressed in currently non-BDNL states.

Adaptations of Breast Imaging Centers to the COVID-19 Pandemic: A Survey of California and Texas

OBJECTIVE

To determine the early impact of the COVID-19 pandemic on breast imaging centers in California and Texas and compare regional differences.

METHODS

An 11-item survey was emailed to American College of Radiology accredited breast imaging facilities in California and Texas in August 2020. A question subset addressed March-April government restrictions on elective services ("during the shutdown" and "after reopening"). Comparisons were made between states with chi-square and Fisher's tests, and timeframes with McNemar's and paired t-tests.

RESULTS

There were 54 respondents (54/240, 23%, 26 California, 28 Texas). Imaging volumes fell during the shutdown and remained below pre-pandemic levels after reopening, with reduction in screening greatest (ultrasound 12% of baseline, mammography 13%, MRI 23%), followed by diagnostic MRI (43%), procedures (44%), and diagnostics (45%). California reported higher volumes during the shutdown (procedures, MRI) and after reopening (diagnostics, procedures, MRI) versus Texas (P = 0.001-0.02). Most screened patients (52/54, 96% symptoms and 42/54, 78% temperatures), and 100% (53/53) modified check-in and check-out. Reading rooms or physician work were altered for social distancing (31/54, 57%). Physician mask (45/48, 94%), gown (15/48, 31%), eyewear (22/48, 46%), and face shield (22/48, 46%) use during procedures increased after reopening versus pre-pandemic (P < 0.001-0.03). Physician (47/54, 87%) and staff (45/53, 85%) financial impacts were common, but none reported terminations.

CONCLUSION

Breast imaging volumes during the early pandemic fell more severely in Texas than in California. Safety measures and financial impacts on physicians and staff were similar in both states.

Impact of the COVID-19 Pandemic on Breast Imaging Education

Objective

To determine the impact of the COVID-19 pandemic on breast imaging education.

Methods

A 22-item survey addressing four themes during the early pandemic (time on service, structured education, clinical training, future plans) was emailed to Society of Breast Imaging members and members-in-training in July 2020. Responses were compared using McNemar's and Mann-Whitney U tests; a general linear model was used for multivariate analysis.

Results

Of 136 responses (136/2824, 4.8%), 96 U.S. responses from radiologists with trainees, residents, and fellows were included. Clinical exposure declined during the early pandemic, with almost no medical students on service (66/67, 99%) and fewer clinical days for residents (78/89, 88%) and fellows (48/68, 71%). Conferences shifted to remote live format (57/78, 73%), with some canceled (15/78, 19%). Compared to pre-pandemic, resident diagnostic (75/78, 96% vs 26/78, 33%) (P < 0.001) and procedural (73/78, 94% vs 21/78, 27%) (P < 0.001) participation fell, as did fellow diagnostic (60/61, 98% vs 47/61, 77%) (P = 0.001) and procedural (60/61, 98% vs 43/61, 70%) (P < 0.001) participation. Most thought that the pandemic negatively influenced resident and fellow screening (64/77, 83% and 43/60, 72%, respectively), diagnostic (66/77, 86% and 37/60, 62%), and procedural (71/77, 92% and 37/61, 61%) education. However, a majority thought that decreased time on service (36/67, 54%) and patient contact (46/79, 58%) would not change residents' pursuit of a breast imaging fellowship.

Conclusion

The pandemic has had a largely negative impact on breast imaging education, with reduction in exposure to all aspects of breast imaging. However, this may not affect career decisions.

Multishot Diffusion-Weighted MRI of the Breast With Multiplexed Sensitivity Encoding (MUSE) and Shot Locally Low-Rank (Shot-LLR) Reconstructions

BACKGROUND

Diffusion-weighted imaging (DWI) has shown promise to screen for breast cancer without a contrast injection, but image distortion and low spatial resolution limit standard single-shot DWI. Multishot DWI methods address these limitations but introduce shot-to-shot phase variations requiring correction during reconstruction.

PURPOSE

To investigate the performance of two multishot DWI reconstruction methods, multiplexed sensitivity encoding (MUSE) and shot locally low-rank (shot-LLR), compared to single-shot DWI in the breast.

STUDY TYPE

Prospective.

POPULATION

A total of 45 women who consented to have multishot DWI added to a clinically indicated breast MRI.

FIELD STRENGTH/SEQUENCES

Single-shot DWI reconstructed by parallel imaging, multishot DWI with four or eight shots reconstructed by MUSE and shot-LLR, 3D T2 -weighted imaging, and contrast-enhanced MRI at 3T.

ASSESSMENT

Three blinded observers scored images for 1) general image quality (perceived signal-to-noise ratio [SNR], ghosting, distortion), 2) lesion features (discernment and morphology), and 3) perceived resolution. Apparent diffusion coefficient (ADC) of the lesion was also measured and compared between methods.

STATISTICAL TESTS

Image quality features and perceived resolution were assessed with a mixed-effects logistic regression. Agreement among observers was estimated with a Krippendorf's alpha using linear weighting. Lesion feature ratings were visualized using histograms, and correlation coefficients of lesion ADC between different methods were calculated.

RESULTS

MUSE and shot-LLR images were rated to have significantly better perceived resolution (P < 0.001), higher SNR (P < 0.005), and a lower level of distortion (P < 0.05) with respect to single-shot DWI. Shot-LLR showed reduced ghosting artifacts with respect to both MUSE (P < 0.001) and single-shot DWI (P < 0.001). Eight-shot DWI had improved perceived SNR and perceived resolution with respect to four-shot DWI (P < 0.005).

DATA CONCLUSION

Multishot DWI enables increased resolution and improved image quality with respect to single-shot DWI in the breast. Shot-LLR reconstructs multishot DWI with minimal ghosting artifacts. The improvement of multishot DWI in image quality increases with an increased number of shots.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 2.

Diffusion-weighted double-echo steady-state with a three-dimensional cones trajectory for non-contrast-enhanced breast MRI

The image quality limitations of echo-planar diffusion-weighted imaging (DWI) are an obstacle to its widespread adoption in the breast. Steady-state DWI is an alternative DWI method with more robust image quality but its contrast for imaging breast cancer is not well-understood. The aim of this study was to develop and evaluate diffusion-weighted double-echo steady-state imaging with a three-dimensional cones trajectory (DW-DESS-Cones) as an alternative to conventional DWI for non-contrast-enhanced MRI in the breast. This prospective study included 28 women undergoing clinically indicated breast MRI and six asymptomatic volunteers. In vivo studies were performed at 3 T and included DW-DESS-Cones, DW-DESS-Cartesian, DWI, and CE-MRI acquisitions. Phantom experiments (diffusion phantom, High Precision Devices) and simulations were performed to establish framework for contrast of DW-DESS-Cones in comparison to DWI in the breast. Motion artifacts of DW-DESS-Cones were measured with artifact-to-noise ratio in volunteers and patients. Lesion-to-fibroglandular tissue signal ratios were measured, lesions were categorized as hyperintense or hypointense, and an image quality observer study was performed in DW-DESS-Cones and DWI in patients. Effect of DW-DESS-Cones method on motion artifacts was tested by mixed-effects generalized linear model. Effect of DW-DESS-Cones on signal in phantom was tested by quadratic regression. Correlation was calculated between DW-DESS-Cones and DWI lesion-to-fibroglandular tissue signal ratios. Inter-observer agreement was assessed with Gwet's AC. Simulations predicted hyperintensity of lesions with DW-DESS-Cones but at a 3% to 67% lower degree than with DWI. Motion artifacts were reduced with DW-DESS-Cones versus DW-DESS-Cartesian (p < 0.05). Lesion-to-fibroglandular tissue signal ratios were not correlated between DW-DESS-Cones and DWI (r = 0.25, p = 0.38). Concordant hyperintensity/hypointensity was observed between DW-DESS-Cones and DWI in 11/14 lesions. DW-DESS-Cones improved sharpness, distortion, and overall image quality versus DWI. DW-DESS-Cones may be able to eliminate motion artifacts in the breast allowing for investigation of higher degrees of steady-state diffusion weighting. Malignant breast lesions in DW-DESS-Cones demonstrated hyperintensity with respect to surrounding tissue without an injection of contrast. LEVEL OF EVIDENCE: 2. TECHNICAL EFFICACY STAGE: 1.

Exactly Solvable System of One-Dimensional Trapped Bosons with Short- and Long-Range Interactions

We introduce a model of trapped bosons with contact interactions as well as Coulomb repulsion or gravitational attraction in one spatial dimension. We find the exact ground-state energy and many-body wave function. The density profile and the pair-correlation function are sampled using Monte Carlo method and show a rich variety of regimes with crossovers between them. Strong attraction leads to a trapped McGuire quantum soliton. Weak repulsion results in an incompressible Laughlin-like fluid with flat density, well reproduced by a Gross-Pitaevskii equation with long-range interactions. Stronger repulsion induces Friedel oscillations and the eventual formation of a Wigner crystal.

Dirac Equation in (1+1)-Dimensional Curved Spacetime and the Multiphoton Quantum Rabi Model

We introduce an exact mapping between the Dirac equation in (1+1)-dimensional curved spacetime (DCS) and a multiphoton quantum Rabi model (QRM). A background of a (1+1)-dimensional black hole requires a QRM with one- and two-photon terms that can be implemented in a trapped ion for the quantum simulation of Dirac particles in curved spacetime. We illustrate our proposal with a numerical analysis of the free fall of a Dirac particle into a (1+1)-dimensional black hole, and find that the Zitterbewegung effect, measurable via the oscillatory trajectory of the Dirac particle, persists in the presence of gravity. From the duality between the squeezing term in the multiphoton QRM and the metric coupling in the DCS, we show that gravity generates squeezing of the Dirac particle wave function.

Dynamical tunneling versus fast diffusion for a non-convex Hamiltonian

This paper attempts to resolve the issue of the nature of the 0.01-0.1 cm(-1) peak splittings observed in high-resolution IR spectra of polyatomic molecules. One hypothesis is that these splittings are caused by dynamical tunneling, a quantum-mechanical phenomenon whereby energy flows between two disconnected regions of phase-space across dynamical barriers. However, a competing classical mechanism for energy flow is Arnol'd diffusion, which connects different regions of phase-space by a resonance network known as the Arnol'd web. The speed of diffusion is bounded by the Nekhoroshev theorem, which guarantees stability on exponentially long time scales if the Hamiltonian is steep. Here we consider a non-convex Hamiltonian that contains the characteristics of a molecular Hamiltonian, but does not satisfy the Nekhoroshev theorem. The diffusion along the Arnol'd web is expected to be fast for a non-convex Hamiltonian. While fast diffusion is an unlikely competitor for longtime energy flow in molecules, we show how dynamical tunneling dominates compared to fast diffusion in the nearly integrable regime for a non-convex Hamiltonian, as well as present a new kind of dynamical tunneling.

Induction of apoptosis in peripheral blood lymphocytes following treatment in vitro with hydroxychloroquine

OBJECTIVE

Defective regulation of apoptosis may be central to the development of autoimmune disorders. This study investigated the possibility that the antirheumatic effect of hydroxycholoroquine (HCQ) may be achieved by up-regulation of apoptosis.

METHODS

Peripheral blood lymphocytes collected from normal controls and patients with systemic lupus erythematosus (SLE) were cultured in the presence or absence of a range of concentrations of HCQ. Cells undergoing apoptosis were identified by several standard methods, including morphologic changes, DNA fragmentation, and flow cytometry. For some experiments, lymphocytes were simultaneously stained with antibodies to T cell surface markers and with propidium iodide for dual-stain flow cytometric studies.

RESULTS

HCQ was able to induce apoptosis in peripheral blood lymphocytes in a dose- and time-dependent manner. HCQ induced these changes in all T cell subpopulations studied. There was no significant difference between the controls and patients with SLE in terms of the percentage of apoptotic cells detected following treatment with HCQ.

CONCLUSION

The present study demonstrated that HCQ induces apoptosis in peripheral blood lymphocytes, which leads to the speculation that HCQ may exert its antirheumatic effect through this mechanism.

Endo-exonuclease of human leukaemic cells: evidence for a role in apoptosis

Inactive forms of endo-exonuclease, activated in vitro by treatment with trypsin, have been identified in human leukaemic CEM and MOLT-4 cells. They comprise over 95% of the total single-strand DNase activity in nuclei and are mainly bound to chromatin and the nuclear matrix. The activated enzyme had Mg2+(Mn2+)-dependent, Ca(2+)-stimulated activities with single- and double-strand DNAs and RNA (polyriboadenylic acid) and other properties characteristic of endo-exonucleases previously described. At least twice as much inactive endo-exonuclease has also been localised in extranuclear compartments of CEM and MOLT-4 cells, 85% bound to the membranes of the endoplasmic reticulum and 15% free in the cytosol. The soluble cytosolic trypsin-activatable endo-exonuclease was immunoprecipitated by antibodies raised independently to both Neurospora and monkey CV-1 cell endo-exonucleases. The free and bound enzymes of both nuclear and extranuclear compartments also cross-reacted on immunoblots with the antibody raised to Neurospora endo-exonuclease to reveal multiple polypeptides ranging in size from 18 to 145 kDa, many of which exhibited activity on DNA gels. The major species bound to the chromatin/matrix were in the 55–63 kDa range. Limited proteolysis of the large polypeptides to those of 18 to 46 kDa accompanied spontaneous chromatin DNA fragmentation to form DNA “ladders' in an isolated nuclei/cytosol system. When the leukaemic cells were treated in culture with either etoposide or podophyllotoxin to induce apoptosis, the largest polypeptides disappeared and smaller endo-exonuclease-related polypeptides of 18 to 46 kDa were detected in the nuclear extracts. The appearance of these polypeptides also correlated with extensive chromatin DNA fragmentation. In addition, there were correlations between the depletion of the major 55–63 kDa species bound to the membranes of the endoplasmic reticulum, depletion of the extranuclear trypsin-activatable activity and the onset and extent of chromatin DNA fragmentation in both cell lines. The extranuclear 55–63 kDa species may be precursors of the chromatin/matrix bound endo-exonuclease. The results indicate that endo-exonuclease plays a role in chromatin DNA degradation in mammalian cells during apoptosis.

Increased tubulin acetylation accompanies reversion to stable ploidy in vincristine-resistant CCRF-CEM cells

The T-cell leukemia line CCRF-CEM is unstable with respect to ploidy, whereas a vincristine-resistant subline, CEM/VCR R, maintains a stable pseudodiploid karyotype. Ploidy change in the parental cells requires the involvement of two cell cycle lesions. The first, in mitosis, prevents cell division after S-phase. The second, in G1, allows a cell with 4N DNA content to re-enter S-phase. We examined differences in expression of tubulin, a major component of the mitotic spindle and the cellular target for vincristine, between the two cell lines. Levels of the beta III isotype were decreased and levels of acetylated alpha-tubulin, a marker for microtubule stability, were increased in the CEM/VCR R cells relative to the parental line, which suggests that the CEM/VCR R cells have a more stable mitotic spindle. Both cell lines exhibit some level of constitutive expression of p53 and c-myc. Constitutive expression of and mutant p53 would contribute to the failure of these cells to recognise G1 checkpoints. Therefore, G1 checkpoint failure and the intrinsically less stable mitotic spindle in the CCRF-CEM cells may contribute to the observed ploidy instability. Conversely, the presence of markers of microtubule stability in the CEM/VCR R cells would predispose them to maintain their ploidy.

Resistance to apoptotic cell death in a drug resistant T cell leukaemia cell line

In this study, we investigated the responses of the T cell leukaemia cell line, CCRF-CEM, and a vincristine-resistant subline, CEM/VCR R, to the induction of cell death by serum withdrawal. This treatment was used to overcome any contribution of P-glycoprotein-mediated drug resistance to the responses of the CEM/VCR R cells. Following serum withdrawal both cell lines exhibited typical apoptotic responses including morphological changes and nucleosomal cleavage of the DNA. However, using several different assays for cell death the CEM/VCR R cell line was shown to undergo apoptosis at a slower rate than the parental CCRF-CEM cell line. Expression of c-Myc, Bcl-2 and p53 was found to be similar in both cell lines, discounting involvement of these proteins in the observed difference in apoptotic response. Given our previous finding that reorganisation of tubulin is involved in apoptosis, we examined the expression of alpha-, beta- and acetylated alpha-tubulin in the parental and resistant lines. The CEM/VCR R cell line had altered tubulin expression when compared to that of the CCRF/CEM line. Transnuclear microtubule networks were observed in log phase CEM/VCR R cells. In addition, increased expression of the acetylated form of the alpha-tubulin isotype suggested that a more stable microtubule network was present in the CEM/VCR R cells. These findings imply that the drug-resistance phenotype in the CEM/VCR R cells may involve the suppression of apoptosis, and that the development of an altered microtubule network may contribute to this suppression.

Tubulin alterations in taxol-induced apoptosis parallel those observed with other drugs

We have described previously that during apoptosis cellular tubulin is reorganized into visible tubulin structures that correlate with apoptotic morphology. Such changes have been observed in human leukaemic cells treated with a variety of cytotoxic agents. These structures are unlike those seen in untreated non-mitotic or mitotic cells. As taxol is known to act by enhancing the polymerization of tubulin in the initiation and extension of microtubules (MTs), and has been shown to induce and stabilize the formation of tubulin structures in a variety of cells, we examined the involvement of tubulin in apoptosis induced by taxol. Apoptosis was induced in a human T-cell leukaemic line, CCRF-CEM, following treatment with 10 nM taxol. The morphological features typical of apoptosis were apparent in taxol-treated cells after drug addition. Immunocytochemical analysis using a monoclonal antibody to beta-tubulin indicated that taxol induced visible tubulin polymerization. DNA fragmentation was detected at 10 hr post-treatment. Flow cytometric analysis of taxol-treated cells showed a time-dependent accumulation of cells in G2/M phase with the appearance of a hypodiploid peak coincident with the detection of DNA fragmentation. Microtubule structures observed following taxol treatment were of three types. At the time of DNA fragmentation, 50% of the cells displayed tubulin structures associated with apoptotic morphology similar to those seen in apoptosis induced by treatment with methotrexate (10(-8) M) or etoposide (17 microM). Twenty percent of the cells were arrested in mitosis at this time. These cells contained either multiple asters or disordered mitotic spindles, and did not display apoptotic morphology. The remaining cells, while normal in morphology, had extensive tubulin polymerization in the cytoplasm and around the nucleus. We examined the time-course of tubulin mRNA expression in apoptosis induced by taxol, methotrexate and etoposide. The level of tubulin mRNA displayed a transient increase after treatment, and prior to the onset of DNA fragmentation with each of the three drugs. These results suggest that during apoptosis taxol induces tubulin changes that display characteristics similar to those observed during apoptosis following treatment with drugs that do not interact directly with tubulin.

Polymerization of tubulin in apoptotic cells is not cell cycle dependent

Prominent, specific tubulin structures were identified in human leukemic cells undergoing apoptosis following treatment with cytotoxic drugs. In order to determine whether tubulin reorganization was dependent upon the stage of the cell cycle at which apoptosis was induced, the human leukemic T-cell line CCRF-CEM was treated with cytotoxic doses of drugs known to arrest cells at different stages of the cell cycle. Apoptosis was confirmed by the detection of characteristic single and multiple nucleosome-sized fragments by agarose gel electrophoresis of isolated DNA. Cells were treated with vincristine, methotrexate, and dexamethasone, which have been shown to induce cell cycle arrest at G2-M, S-phase, and G1, respectively. Treated and untreated cells were analyzed by immunocytochemistry for beta-tubulin or Ki-67 antigen (to confirm cell cycle phase) and scored for apoptotic morphology. Dual staining for cellular tubulin and DNA content, measured by flow cytometry, was used to confirm the stage at which the cycling cells arrested. Increased total cellular tubulin immunofluorescence was observed in treated compared to untreated cells. Our results indicate that CCRF-CEM cells undergo apoptosis (identified morphologically) at all stages of the cell cycle except mitosis. We conclude that the reorganization of cellular tubulin that we have observed in apoptotic cells is independent of the tubulin involvement in cell division and thus may be an integral part of the apoptotic process.

Establishment of an in vitro model for cisplatin resistance in human neuroblastoma cell lines

Two unique cisplatin-resistant neuroblastoma (NB) cell lines have been derived from the established lines IMR-32 and SK-N-SH by treatment with escalating doses of cisplatin. IMR/CP.20 was 6.6-fold and SK/CP.15 was 3.8-fold more resistant to the cytotoxic effects of cisplatin than the parent lines. The parent SK-N-SH cells were 16.6-fold more resistant to the effects of cisplatin than IMR-32 cells. The cisplatin-resistant cell lines demonstrated alterations to their morphology, but there was no change in the cell growth characteristics of the resistant compared to the sensitive lines. Cytogenetic analysis revealed that clonal selection of parental subclones had occurred with additional chromosomal changes in both resistant lines. Both IMR/CP.20 and SK/CP.15 lines were cross-resistant to aphidicolin and to L-phenylalanine mustard. The IMR/CP.20 line was 7.3-fold more resistant to mitomycin C than the parent line. Neither cisplatin-resistant NB line was cross-resistant to 5-fluorouracil, etoposide or doxorubicin. All NB lines had low levels of DNA repair compared to HeLa or CHO-K1 cells. However, the IMR/CP.20 cell line showed a significantly higher ability to effect DNA repair than the parent IMR-32 line, indicating that the increased resistance to cisplatin observed in this line may, in part, be due to an enhanced DNA repair capacity.

Heterotransplantation of early B-lineage acute lymphoblastic leukemia using a solubilized attachment matrix (Matrigel)

Maintenance of long term culture and conventional xenografting of early B-lineage acute lymphoblastic leukemia cells is most difficult. Matrigel, a solubilized attachment matrix shown to aid growth of anchorage dependent solid tumors, was studied in heterotransplantation. Material for xenografting was derived from 5 patient bone marrow aspirates and 5 cell lines previously established and maintained by intraocular inoculation in nude mice. Specimens were injected by 3 methods: intraocular (n = 397); s.c. in medium (n = 78); and s.c. in medium supplemented by Matrigel (n = 69). With intraocular injection, 6 of 10 cell sources grew with respective ingraftment rates of 29-76%. Using the conventional s.c. method, no tumors resulted. The addition of Matrigel produced s.c. ingraftment from 8 of 10 cell sources (ingraftment rate, 50-100%). Immunophenotype, histopathology, and karyotype of the cells derived after Matrigel dependent ingraftment correlated with the cells of origin. It is concluded that Matrigel enables establishment and maintenance of early B-lineage acute lymphoblastic leukemia cell growth in a s.c. xenograft model.

Karyotypic analysis of CCRF-CEM and drug-resistant cell lines with stable and unstable ploidy

Karyotypic studies were performed on methotrexate (MTX)- and vincristine (VCR)-resistant cell lines derived from the human T-cell leukemia CCRF-CEM cell line. We noted karyotypic selection and additional chromosome change associated with acquisition of drug-resistance. Furthermore, we observed that both the parental and MTX-resistant sublines, CEM/MTX R1-3, had a tendency to ploidy change. Karyotypic studies of malignant cells have shown that polyploidy is frequently a consequence of a single sporadic event, followed by growth and selection of the polyploid clone [1]. In this study, however, various karyotypic clones were identified with near- and pseudotetraploid karyotypes that appeared to be derived from different near- and pseudodiploid sidelines. Polyploidy was invariably associated with loss of at least two of the four chromosomes 8 whether the pseudodiploid sideline from which it was derived carried one or both chromosomes 8. In contrast, neither polyploid clones nor loss of chromosome 8 was noted in the CEM/VCR R cells.

Phenotypic and cytogenetic analysis of atypical multidrug resistance in human leukaemic cells selected with methotrexate at high concentration

A series of CCRF-CEM sublines selected for extreme resistance to methotrexate has been shown previously to exhibit cross resistance to a number of agents belonging to the multidrug resistance phenotype. The mechanism(s) underlying resistance to vincristine, vinblastine and actinomycin D in the most resistant subline (CEM/MTX R3) has now been investigated. Efflux of [3H]vincristine was more rapid in CEM/MTX R3 than in either CCRF-CEM cells or a methotrexate-resistant subline not refractory to Vinca alkaloids. In addition, verapamil completely reversed resistance to vincristine, vinblastine and actinomycin D in the CEM/MTX R3 cells. While these results are suggestive of P-glycoprotein-mediated multidrug resistance, Northern analysis revealed no detectable expression of the mdr 1/gene in CEM/MTX R3 cells. Likewise, karyotypic analysis of the resistant subline, while revealing certain clonal abnormalities, provided no evidence of alteration in the mdr 1/gene locus on chromosome 7. The data suggest therefore the operation, in these cells, of a novel mechanism of resistance.

Cytogenetic basis of acute myeloid leukemia

The chromosomes of 12 adult patients with acute leukemia were analyzed by conventional means and by Giemsa and centromeric banding techniques. Acute myeloblastic leukemia was diagnosed in 7, acute myelomonocytic leukemia in 2, and acute undifferentiated leukemia in 3. Bone marrow was aspirated from patients when in relapse or remission, and both euploid and aneuploid cells were examined. All patients showed trisomy no. 9 and many showed additional numerical or structural changes in some or all their cells. These changes included monosomy no. 21 and/or monosomy no. 8. The proportion of trisomy no. 9 cells was 30-50% in patients in full remission and up to 100% in patients in relapse; thus trisomy no. 9 might be an important marker of leukemic cells. A mechanism was proposed to explain the induction and selection of the trisomy no. 9 karotype.

Letter: Consistent chromosome abnormalities in acute leukaemia

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