Using CDKN2A loss in the context of wildtype TP53 to predict sensitivity for the MDM2 inhibitor milademetan

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Background: MDM2 is an E3 ubiquitin ligase that plays a critical role in the degradation of the tumor suppressor p53. Milademetan (RAIN-32) is an orally available, small molecule inhibitor of MDM2 that disrupts the MDM2-p53 complex thereby restoring p53 activity. Approximately 50% of tumors harbor wildtype (WT) TP53 and thus may be susceptible to strategies that reactivate p53. The CDKN2A gene is altered in more than 15% of all tumors (TCGA PanCancer Atlas) and encodes two proteins, p14ARF and p16, which are inhibitors of p53 and cyclin dependent kinases, respectively. Given the role of p14ARF in regulating the MDM2-p53 pathway, we investigated the use of CDKN2A loss in the context of WT TP53 as a strategy for selection of patients who might benefit from milademetan. Methods: N/A. Results: We evaluated the sensitivity of 215 cancer cell lines to milademetan treatment (Ishizawa et al., 2018) by CDKN2A and TP53 status. The median IC50 of CDKN2A homozygous (HZ) loss vs. non-HZ loss was 8,620 vs. 10,000 nM. However, when we assessed CDKN2A HZ loss with WT TP53 versus mutant TP53 the median IC50 was 79.5 vs. 10,000 nM demonstrating that the use of both CDKN2A and TP53 was better able to discriminate sensitive vs. resistant cell lines. To validate these in vitro findings, we tested milademetan in 5 xenograft models with CDKN2A HZ loss and WT TP53, all of which demonstrated tumor growth inhibition with milademetan. As suppression of p53 activity by MDM2 amplification (Kato et al. 2017) or CDKN2A loss (Adib et al. 2021) has been associated with resistance to immune checkpoint inhibitors (ICI), we also tested the combination of anti-PD1 with milademetan in the colon-26 syngeneic model ( CDKN2A HZ loss) and observed a significant enhancement in tumor growth inhibition compared to milademetan or anti-PD1 alone. Based on the differential sensitivity to milademetan using both CDKN2A loss and WT TP53 status we evaluated TCGA Pan-Cancer Atlas data to estimate the frequency of these genetic co-alterations. Among solid tumors types the most frequent percentage of these co-alterations included glioblastoma, mesothelioma, melanoma, bladder, sarcoma, pancreatic and NSCLC. Overall, the percentage of all tumors with co-alteration of CDKN2A HZ loss and WT TP53 was 6.2%. Patients with CDKN2A HZ loss had a significantly worse overall survival than those without CDKN2A HZ loss (median OS of 29.7 vs. 97.4 months, p < 0.0001), and this was maintained when accounting for tumor type in multivariate analysis (p < 0.0001). Conclusions: Milademetan showed evidence of preclinical anti-tumor activity across multiple tumor types with CDKN2A loss and WT TP53. In vivo data supported potential synergy of milademetan with an ICI in this genetic subset. A clinical trial evaluating the safety and efficacy of milademetan plus atezolizumab in advanced solid tumors with CDKN2A HZ loss and WT TP53 (MANTRA-4) is planned.

[A Case of Pediatric Soft Tissue Sarcoma with LMNA-NTRK1 Gene Fusion Treated with Larotrectinib under Single Patient Expanded Access System]

Tropomyosin-related kinase(TRK)fusion proteins are oncogenic drivers in multiple tumors in adults and children.Larotrectinib, an orally administered selective TRK inhibitor approved in the US, exhibits inhibitory activity against tumors harboring TRK fusions and is well tolerated.Here, we report the case of an 8-year-old female child with recurrence of an NTRK fusion low-grade sarcoma treated with larotrectinib monotherapy.The patient previously underwent resection of low-grade sarcoma in the right brachialis at 6 years of age, but local recurrence occurred after 16 months.As re-operation likely required amputation, larotrectinib was commenced at a dose of 100 mg BID.Complete radiographic remission was achieved after 3 months.There were no adverse events attributed to larotrectinib treatment.After dosing for 6 months, we performed local resection, confirming pathological complete remission.The drug was stopped, and the patient showed no evidence of relapse at 4 months after resection.In this case, larotrectinib was obtained using Single Patient Expanded Access under the FDA.In this paper, we also discuss the issues faced while accessing unapproved drugs in the precision medicine era in Japan.

Abstract CT127: Phase I and expanded access experience of LOXO-195 (BAY 2731954), a selective next-generation TRK inhibitor (TRKi)

Background: Larotrectinib, a selective TRKi, is now FDA approved for pediatric and adult TRK-fusion solid tumors, regardless of tumor origin. Emergent TRK kinase mutations are a common mechanism of resistance to TRKis. LOXO-195, a selective TRKi, was developed to maintain potency against multiple TRK kinase domain mutations.

Methods: Patients (pts) received LOXO-195 via a Phase I study (NCT03215511, n=20) or FDA expanded access single patient protocol (SPP, n=11). Eligible pts were ≥4-weeks old with a locally identified TRK fusion and had progressed or were intolerant to at least 1 priorTRKi. Parallel 3+3 dose escalations were pursued in adults and children, with intra-patient dose escalation permitted based on tolerance and pharmacokinetics. Pts aged &lt;12 received BSA-adjusted doses.

Results: As of 03-DEC-2018, a total of 31 TRK-fusion pts (7 children, 24 adults) with 11 cancer types had been treated. Median duration on last prior TRKi was 9.5 months (range, 2-30). In the Phase 1, doses of 32 mg QD to 150mg BID were explored, and TEAEs (all grades/cause, in &gt;3 pts) were dizziness/ataxia (65%), nausea/vomiting (50%), anemia (30%), myalgia, abdominal pain, fatigue, & lymphopenia (all 20%). Five Phase I pts (all adults) had DLTs: ataxia/dizziness (4), and ataxia/vomiting (1). For the SPPs: 1 pt dose-reduced and none discontinued for a TEAE. Cmax at doses ≥50 mg exceeded the predicted IC50 for TRK kinase mutations. Pretreatment tissue and/or plasma, as available, defined TRK kinase mutation status. Preliminary efficacy overall, and by TRK kinase mutation status, is shown in the Table.

Discussion: LOXO-195 had preliminary efficacy in pts with resistance to prior TRKi mediated by TRK kinase mutations. The subset of pts who develop TRK-independent resistance are unlikely to benefit from LOXO-195. Dose selection is ongoing in both children and adults.

Confirmed best overall response, all dose levels, investigator assessed per RECIST 1.1 (n=29≠)Patient CohortTotal Patients,nCR/PR, nStable Disease, nPD, nNon- evaluable, †nORRTRK Kinase Mutation20963245% (9/20)Solvent Front14742150% (7/14)Gatekeeper4111125% (1/4)xDFG2110050% (1/2)Identified bypass300210% (0/3)Other/ Unknown*61#31117% (1/6)Overall291096434% (10/29)≠ 2 pts still on study drug and awaiting 1st response assessment not included in Table.† 4 pts non-evaluable: 1 discontinued drug for unrelated new cancer diagnosis &lt;28 days after start of study drug and 3 withdrew within 14 days of study drug start.* Includes 1 pt with no identified TRK kinase resistance mutationor bypass alteration# and 5 pts who could not be tested.# Pt intolerant but not resistant to prior TRKi

Citation Format: David Hyman, Shivaani Kummar, Anna Farago, Birgit Geoerger, Morten Mau-Sorensen, Matthew Taylor, Elena Garralda, Ramamoorthy Nagasubramanian, Michael Natheson, Lucy Song, Michael Capra, Mette Jorgensen, Alan Ho, Neerav Shukla, Steve Smith, Xin Huang, Brian Tuch, Nora Ku, Theodore W. Laetsch, Alexander Drilon, David Hong. Phase I and expanded access experience of LOXO-195 (BAY 2731954), a selective next-generation TRK inhibitor (TRKi) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT127.

Larotrectinib efficacy and safety in adult TRK fusion cancer patients

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Background: A broad range of pediatric and adult malignancies harbor TRK fusions involving the NTRK1, NTRK2, and NTRK3 genes. The highly-selective TRK inhibitor, larotrectinib, has previously shown a high overall response rate (ORR) and a favorable safety profile in patients (pts) with TRK fusion cancer. To better delineate efficacy in adults, as pediatric pts have a particularly high ORR, here we report updated efficacy and safety data from the adult subset of pts with TRK fusion cancer treated with larotrectinib. Methods: Adult pts (aged 18 or older) with TRK fusion cancer detected by local testing in 2 larotrectinib clinical trials (NCT02122913 and NCT02576431) were analyzed. Larotrectinib was administered 100 mg PO BID until disease progression, withdrawal, or unacceptable toxicity. Disease status was assessed by both investigator (INV) and independent assessment (IRC) using RECIST v1.1. Results: As of July 30, 2018, 83 adults (median age: 57 y, range 20–80 y) with TRK fusion cancer had been treated. Cancer types included salivary gland (23%) and thyroid cancer (19%), soft tissue sarcoma (14%), lung cancer (13%), colon cancer and melanoma (7% each), GIST (5%), and bone sarcoma, cholangiocarcinoma, and appendiceal, breast, and pancreas cancer (≤2% each). TRK fusions involved NTRK1 (40%), NTRK2 (2%), and NTRK3 (57%). 77% of pts had received prior systemic therapy (median lines: 2, range 0–10). In 74 pts evaluable per INV, the ORR was 76% with 9% CR, 57% confirmed PR, 9% PR pending confirmation, 12% SD, 11% PD, and 1% not determined; 9 pts were non-evaluable (NE) due to lack of post-baseline assessment. In 65 pts evaluable per IRC, the ORR was 68% with 17% CR, 51% PR, 15% SD, 12% PD, and 5% NE. With a median follow up of 17.2 and 17.5 mo per INV and IRC, respectively, the median duration of response had not been reached (ranges identical: 1.9+ to 38.7+ months). At data cutoff, 63% remained on treatment; 30% had discontinued due to disease progression. Adverse events were mostly grade 1–2. Conclusions: Larotrectinib demonstrated robust tumor-agnostic efficacy and a favorable safety profile in adult pts with TRK fusion cancer. These results support testing for TRK fusion cancer in pts with advanced solid tumors, regardless of site of primary diagnosis. Clinical trial information: NCT02122913 and NCT02576431.

Activity of larotrectinib in TRK fusion cancer patients with brain metastases or primary central nervous system tumors

2006

Background: TRK fusions are oncogenic drivers of a variety of cancers, many of which can involve the central nervous system (CNS). Larotrectinib is an FDA-approved selective TRK inhibitor for the treatment of TRK fusion cancer (Drilon et al, NEJM 2018). While larotrectinib has been shown to cross the blood–brain barrier (Ziegler et al, Br J Cancer 2018), its clinical activity in a series of TRK fusion cancers with primary or metastatic intracranial disease has not been described. Methods: Patients (pts) with non-primary CNS solid tumors with brain metastases, or primary CNS tumors harboring a TRK fusion treated with larotrectinib in 2 clinical trials (NCT02637687, NCT02576431) were identified. Larotrectinib was administered until disease progression (PD), withdrawal, or unacceptable toxicity. Disease status was investigator-assessed (RANO and RECIST). Data cutoff: July 30, 2018. Results: 14 pts were identified: 5 non-primary CNS solid tumors (3 lung cancer, 2 thyroid cancer; fusion type: 2 ETV6-NTRK3, 2 SQSTM1-NTRK3, 1 EPS15-NTRK1; age range 25–79 y) and 9 primary CNS tumors (3 glioma, 2 glioblastoma, 1 astrocytoma, 3 NOS; fusion type: 3 BCR-NTRK2, 2 KANK-NTRK2, 1 each of AFAP1-NTRK1, AGTPBP1-NTRK2, ETV6-NTRK3, SPECC1L-NTRK2; age range 2–79 y). In the 5 pts with non-primary CNS tumors, the best objective response to therapy was PR in 3 (60%, 1 pending confirmation), SD in 1 (20%), and not evaluable (NE) in 1 (20%). Duration of response ranged from 9+ to 13 mo. In the 9 pts with primary CNS tumors, disease control was achieved in all evaluable pts (primary PD not observed; 1 pt required dose increase). The best objective response to therapy was PR in 1 (11%; pending confirmation, −55% tumor shrinkage, ongoing at 3.7 mo), SD in 7 (78%; tumor shrinkage range −1% to −24% for pts with measurable disease, 5 had SD > 4 mo), and NE in 1 (11%). Duration of treatment ranged from 2.8–9.2+ mo. Conclusions: Larotrectinib is active in pts with TRK fusion cancers with intracranial disease. Confirmed responses and durable disease control were seen in metastatic disease and primary CNS tumors of various histologies. These results further support expanded testing for TRK fusions across all cancers, including primary CNS tumors. Clinical trial information: NCT02637687 and NCT02576431.

Molecular characterization and management of secondary resistance to serial TRK inhibitors

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Background: TRK inhibitor drugs such as the highly selective larotrectinib (Laro), have proven highly effective in malignancies harboring fusions of NTRK1, 2, or 3. Resistance in patients (pts) with progressive disease (PD) after response to initial TRK inhibitor therapy has been attributed to secondary mutations in the solvent front or gatekeeper domains of the NTRK fusion gene. LOXO-195 (L195) is a 2nd generation TRK inhibitor that overcomes these mutations. Mechanisms of resistance to L195 have not yet been well characterized. Methods: We analyzed molecular mechanisms of resistance in one adult pt with undifferentiated pleomorphic sarcoma (UPS) who had serial responses and PD on Laro and L195. Targeted DNA sequencing, RNA sequencing and multicolor cyclic immunofluorescence (CyCIF) were performed on pre- and post-PD specimens on both drugs. Results: The patient was enrolled on the phase 2 clinical trial of Laro (NCT02576431) with TPM3-NTRK1 fusion UPS. Multifocal PD and resistance to Laro developed after major objective response RECIST -74.9%, of 10 months (mo); the resistant tumor harbored both the initial TPM3-NTRK1 fusion but also evolved a new solvent front mutation in NTRK1 [c.1783G > A (p.G595R)]. A single pt protocol (NCT03206931) was designed to treat with L195. After an initial response to L195, PD limited to 2 sites developed; both sites were resected at 5 and 10 mo. The pt continues on L195 with systemic disease control 20 mo after initiation (in total 30 mo since Laro initiation). Analysis of tumor samples pre- and post-PD on L195 identified the emergence of a KRAS G12V mutation, with associated activation of the KRAS signaling pathway and a significant infiltration by inflammatory cells. A cell line and pt-derived xenografts (PDX), all harboring the initial TPM3-NTRK1 fusion, were generated from this pt. Conclusions: Resection of oligoclonal PD and continuation of L195 post-PD can be an effective treatment strategy. Oncogenic activation of the KRAS pathway is a possible mechanism of resistance to L195. Our studies indicate that the tumor microenvironment of TRK-fusion sarcomas resistant to TRK inhibitors may increase inflammatory cell infiltrates, which may provide clues for future combination therapy.

Oncogenic TRK fusions are amenable to inhibition in hematologic malignancies

Rearrangements involving the neurotrophic receptor kinase genes (NTRK1, NTRK2, and NTRK3; hereafter referred to as TRK) produce oncogenic fusions in a wide variety of cancers in adults and children. Although TRK fusions occur in fewer than 1% of all solid tumors, inhibition of TRK results in profound therapeutic responses, resulting in Breakthrough Therapy FDA approval of the TRK inhibitor larotrectinib for adult and pediatric patients with solid tumors, regardless of histology. In contrast to solid tumors, the frequency of TRK fusions and the clinical effects of targeting TRK in hematologic malignancies are unknown. Here, through an evaluation for TRK fusions across more than 7,000 patients with hematologic malignancies, we identified TRK fusions in acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), histiocytosis, multiple myeloma, and dendritic cell neoplasms. Although TRK fusions occurred in only 0.1% of patients (8 of 7,311 patients), they conferred responsiveness to TRK inhibition in vitro and in vivo in a patient-derived xenograft and a corresponding AML patient with ETV6-NTRK2 fusion. These data identify that despite their individual rarity, collectively, TRK fusions are present in a wide variety of hematologic malignancies and predict clinically significant therapeutic responses to TRK inhibition.

A Next-Generation TRK Kinase Inhibitor Overcomes Acquired Resistance to Prior TRK Kinase Inhibition in Patients with TRK Fusion-Positive Solid Tumors

Larotrectinib, a selective TRK tyrosine kinase inhibitor (TKI), has demonstrated histology-agnostic efficacy in patients with TRK fusion-positive cancers. Although responses to TRK inhibition can be dramatic and durable, duration of response may eventually be limited by acquired resistance. LOXO-195 is a selective TRK TKI designed to overcome acquired resistance mediated by recurrent kinase domain (solvent front and xDFG) mutations identified in multiple patients who have developed resistance to TRK TKIs. Activity against these acquired mutations was confirmed in enzyme and cell-based assays and in vivo tumor models. As clinical proof of concept, the first 2 patients with TRK fusion-positive cancers who developed acquired resistance mutations on larotrectinib were treated with LOXO-195 on a first-in-human basis, utilizing rapid dose titration guided by pharmacokinetic assessments. This approach led to rapid tumor responses and extended the overall duration of disease control achieved with TRK inhibition in both patients.Significance: LOXO-195 abrogated resistance in TRK fusion-positive cancers that acquired kinase domain mutations, a shared liability with all existing TRK TKIs. This establishes a role for sequential treatment by demonstrating continued TRK dependence and validates a paradigm for the accelerated development of next-generation inhibitors against validated oncogenic targets. Cancer Discov; 7(9); 963-72. ©2017 AACR.See related commentary by Parikh and Corcoran, p. 934This article is highlighted in the In This Issue feature, p. 920.

Clinical Safety and Immunogenicity of Tumor-Targeted, Plant-Made Id-KLH Conjugate Vaccines for Follicular Lymphoma

We report the first evaluation of plant-made conjugate vaccines for targeted treatment of B-cell follicular lymphoma (FL) in a Phase I safety and immunogenicity clinical study. Each recombinant personalized immunogen consisted of a tumor-derived, plant-produced idiotypic antibody (Ab) hybrid comprising the hypervariable regions of the tumor-associated light and heavy Ab chains, genetically grafted onto a common human IgG1 scaffold. Each immunogen was produced in Nicotiana benthamiana plants using twin magnICON vectors expressing the light and heavy chains of the idiotypic Ab. Each purified Ab was chemically linked to the carrier protein keyhole limpet hemocyanin (KLH) to form a conjugate vaccine. The vaccines were administered to FL patients over a series of ≥6 subcutaneous injections in conjunction with the adjuvant Leukine (GM-CSF). The 27 patients enrolled in the study had previously received non-anti-CD20 cytoreductive therapy followed by ≥4 months of immune recovery prior to first vaccination. Of 11 patients who became evaluable at study conclusion, 82% (9/11) displayed a vaccine-induced, idiotype-specific cellular and/or humoral immune response. No patients showed serious adverse events (SAE) related to vaccination. The fully scalable plant-based manufacturing process yields safe and immunogenic personalized FL vaccines that can be produced within weeks of obtaining patient biopsies.

Impact of direct physician-to-physician contact on accelerating oncology clinical trial accrual

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Background: The development of more effective oncology agents is critically dependent on the completion of clinical trials; currently, >4000 oncology trials listed in www.clinicaltrials.gov are accruing pts in the US. Unfortunately, only 3–5% of new cancer pts participate in clinical trials and most trials do not meet their projected accrual timelines. Barriers to pt accrual include physician awareness & attitudes, access to protocols, administrative burdens to conduct clinical trials, cost to physicians and pts, and pt concerns about participation in research trials. To overcome at least some of these barriers, we investigated a strategy to improve clinical trial accrual that optimizes trial placement and awareness through a direct physician to physician intervention. Methods: For each site, a customized enrollment plan is established after initial assessment of interest and accrual potential. Implementation of the enrollment plan includes clinical communications and medical support delivered through direct physician to physician interactions. From Feb 2008 to December 2008, we implemented this strategy to increase accrual to 5 oncology trials (2 placebo controlled randomized trials and 3 phase II trials in breast cancer, non-Hodgkin's lymphoma and soft tissue sarcoma). Results: The implementation of direct physician to physician intervention resulted in a measurable improvement of between 50 - 300% in the monthly accrual to each of these 5 trials. Despite being significantly behind projections, 2 of the trials have now completed accrual on schedule. In the ongoing phase III study, accrual has improved from an average of 3.8 pts/mo to 13.5 pts/mo. Conclusions: The use of our current model of optimizing trial placement and awareness through a direct physician to physician intervention has been successful in significantly accelerating clinical trial accrual in 5/5 trials initiated to date.

[Table: see text]

[Table: see text]

Does delay of adjuvant chemotherapy affect the clinical outcome in patients with colon cancer?

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Background: Adjuvant chemotherapy (AC) in patients with stage III colon adenocarcinoma prevents recurrences and improves survival. Although most trials mandate initiation of AC within 8 weeks of resection, the impact of timing of AC is still not clear with few studies reporting conflicting results. We hypothesized that AC commenced within 60 days of resection would increase survival in patients with stage II and III colon cancer. Methods: Patients with newly diagnosed stage II or III colon adenocarcinoma who received fluoropyrimidine based AC in two centers (a private cancer center and a large community hospital) between 2000 and 2007 were included into analysis. Time to adjuvant chemotherapy (TTC), overall survival (OS), and relapse-free survival (RFS) were calculated from the surgery date. Patients were dichotomized into early- (group 1) and late-treatment (group 2) groups using the TTC of 60 days. The demographic, clinical, and laboratory characteristics of patients in two groups were compared using chi-square and t-test. Kaplan-Meier survival curves were constructed employing univariate log-rank test to assess the effects of demographic and clinical characteristics on OS. Then the impact of TTC on OS and RFS was analyzed using a Cox proportional hazard model incorporating the significant factors found in the univariate analysis. Results: 190 patients were eligible for the study (median age: 57 yrs [range 14–84]). 116 patients (61%) were female and 35 patients (18%) had stage II disease. Median TTC was 49 days (range 24–196) and median follow-up was 143 weeks (range 9–451). 134 patients (70%) received AC within 60 days of surgery (group 1) and 56 (30%) received after (group 2). The only difference between the two groups was the higher N stage in group 1. The treating hospital and the N stage were found to be the factors affecting the OS in univariate analysis. Five-year OS for group I was 75.2% as compared to 61.3% for group II (HR 2.11, CI: 1.00–4.45, p=0.049). Five-year RFS for group I was 65.7% as compared to 59.0% for group II (HR: 1.19, CI: 0.65–2.20, p=0.570). Conclusions: Delay of AC more than 60 days after resection is associated with inferior survival in stage II/III colon cancer.

No significant financial relationships to disclose.

Sentinel node biopsy in ductal carcinoma in situ patients

BACKGROUND

Sentinel lymph node (SLN) mapping is an effective and accurate method of evaluating the regional lymph nodes in breast cancer patients. The SLN is the first node that receives lymphatic drainage from the primary tumor. Patients with micrometastatic disease, previously undetected by routine hematoxylin and eosin (H&E) stains, are now being detected with the new technology of SLN biopsy, followed by a more detailed examination of the SLN that includes serial sectioning and cytokeratin immunohistochemical (CK IHC) staining of the nodes.

METHODS

At Moffitt Cancer Center, 87 patients with newly diagnosed pure ductal carcinoma in situ (DCIS) lesions were evaluated by using CK IHC staining of the SLN. Patients with any focus of microinvasive disease, detected on diagnostic breast biopsy by routine H&E, were excluded from this study. DCIS patients, with biopsy-proven in situ tumor by routine H&E stains, underwent intraoperative lymphatic mapping, using a combination of vital blue dye and technetium-labeled sulfur colloid. The excised SLNs were examined grossly, by imprint cytology, by standard H&E histology, and by IHC stains for CK. All SLNs that had only CK-positive cells were subsequently confirmed malignant by a more detailed histological examination of the nodes.

RESULTS

CK IHC staining was performed on 177 SLNs in 87 DCIS breast cancer patients. Five of the 87 DCIS patients (6%) had positive SLNs. Three of these patients were only CK positive and two were both H&E and CK positive. Therefore, routine H&E staining missed microinvasive disease in three of five DCIS patients with positive SLNs. In addition, DCIS patients with occult micrometastatic disease to the SLN underwent a complete axillary lymph node dissection, and the SLNs were the only nodes found to have metastatic disease. Of interest, four of the five node-positive patients had comedo carcinoma associated with the DCIS lesion, and one patient had a large 9.5-cm low grade cribriform and micropapillary type of DCIS.

CONCLUSIONS

This study confirms that lymphatic mapping in breast cancer patients with DCIS lesions is a technically feasible and a highly accurate method of staging patients with undetected micrometastatic disease to the regional lymphatic basin. This procedure can be performed with minimal morbidity, because only one or two SLNs, which are at highest risk for containing metastatic disease, are removed. This allows the pathologist to examine the one or two lymph nodes with greater detail by using serial sectioning and CK IHC staining of the SLNs. Because most patients with DCIS lesions detected by routine H&E stains do not have regional lymph node metastases, these patients can safely avoid the complications associated with a complete axillary lymph node dissection and systemic chemotherapy. However, DCIS patients with occult micrometastases of the regional lymphatic basin can be staged with higher accuracy and treated in a more selective fashion.

B cell dysfunction after bone marrow transplantation is associated with decreased Ca2+ flux upon membrane Ig crosslinking

Patients undergoing bone marrow transplantation have a long-lasting defect of B cell-mediated immunity. Both quantitative (decreased blood B cell counts) and qualitative (decreased Ig production) abnormalities of B cells have been described. To better understand the mechanism of the qualitative defect and its potential relation to B cell immaturity, we studied the in vitro responsiveness of B cells to polyclonal stimuli in patients at 2-12 months post-transplant and in normal neonates. Several key steps of the B cell program were deficient in the patients while they were relatively normal in the neonates. These included (i) early activation as assessed by Ca2+ flux; (ii) late activation as assessed by the increase in cell size and upregulation of the activation antigens CD25 and CD71; and (iii) proliferation as assessed by the number of cycling cells after stimulation. We conclude that the functional B cell defect during the early (< 1 year) post-transplant period extends back to the level of early activation and cannot be simply attributed to the relative immaturity of post-transplant B cells.

Selective depletion of CD8+ cells for prevention of graft-versus-host disease after bone marrow transplantation. A randomized controlled trial

We performed a prospective randomized, double-blind study to assess the efficacy of selective depletion of CD8+ bone marrow cells in preventing acute graft-versus-host disease (GVHD) in 38 patients undergoing HLA-identical sibling donor bone marrow transplantation for leukemia. All patients received CsA for GVHD prophylaxis. Nineteen patients received marrow depleted of CD8+ cells by ex vivo treatment with anti-leu2, an anti-CD8 mAb and complement; four patients had moderate (grade 1 or 2 acute GVHD) and the only patient who experienced grade 3 manifestations was a technical failure. The control group consisted of 19 patients who received unmodified bone marrow; one patient had grade 1, 4 patients had grade 2, and 10 had grade 3 or 4 acute GVHD. The actuarial incidence of grade > or = 2 acute GVHD was 20 +/- 20% in the CD8-depleted group compared with 80 +/- 18% in the controls (P = 0.004). Death in 5 of the control patients and the single patient in whom CD8 depletion was a technical failure was related to acute GVHD. Graft failure occurred in 2 patients in the CD8-depleted group and in none of the controls. Leukemic relapse occurred in 2 patients receiving CD8-depleted bone marrow and 2 patients in the control group. Seven patients receiving marrow depleted of CD8+ cells are alive and free of leukemia and 9 patients in the control group are alive, 7 of whom remain leukemia-free (P = 0.88). The 3-year actuarial leukemia-free survival is 37 +/- 22% of the CD8-depleted group and 36 +/- 22% for the control group. These results indicate that selective depletion of CD8+ cells from the bone marrow significantly reduces the incidence and severity of acute GVHD.

B cell reconstitution after human bone marrow transplantation: recapitulation of ontogeny?

Patients undergoing BMT have a long-lasting defect of B cell-mediated immunity, especially if chronic GVHD ensues. It has been postulated that the post-transplant B cell abnormalities can be explained by the recapitulation of B cell ontogeny. To test this hypothesis, we studied the quantitative and phenotypic reconstitution of circulating B cells in 24 transplant recipients and compared it with normal ontogeny. The results confirm that a second round of ontogeny occurs in transplant recipients without chronic GVHD. This was evidenced by the pattern of quantitative B cell reconstitution (low-->high-->normal B cell counts), large B cell size and a high proportion of B cells overexpressing CD38, membrane IgM (mIgM) and membrane IgD (mIgD). The recapitulation of ontogeny was blunted in most patients with chronic GVHD, as evidenced by the absence of the overshoot of total B cells and by the relative lack of CD38high, mIgMhigh and mIgDhigh B cells. We conclude the post-transplant B cell development in patients without chronic GVHD parallels ontogeny. The limited ability of patients with chronic GVHD to re-enact B cell ontogeny may contribute to their longer-lasting and more severe humoral immunodeficiency.

Mammotroph autoregulation: uptake of secreted prolactin and inhibition of secretion

A dissociated preparation of normal adult rat pituitary cells has been used to study PRL autoregulation at the level of the mammotroph . Female rat pituitary cells previously cultured for 48 h on polylysine-coated petri dishes were washed to remove serum and accumulated PRL and then incubated in fresh medium in the absence or presence of increasing concentrations of rat PRL. Accurate balance sheets, allowing for degradation and nonspecific adsorption of PRL, showed exogenous PRL to regulate the amount of PRL released by the cells. That this regulation was partly produced by uptake of secreted PRL from the medium was demonstrated by supplementing the medium with [125I]iodo-rat PRL. Inhibition of secretion also played a role and was implied by experiments showing that ease of reversal of the inhibition was inversely proportional to the density of cell culture, which was itself proportional to the amount of PRL in the medium and the duration of autoregulation. These results indicate that normal adult rat pituitary cells in primary culture are capable of regulating the amount of PRL in their external milieu and that uptake of already secreted PRL is an important component of the regulatory mechanism.