Subcutaneous Leiomyosarcoma: An Aggressive Malignancy Portending a Significant Risk of Metastasis and Death

Subcutaneous leiomyosarcoma (LMS) is a rare, poorly understood variant. The current literature on the subject is sparse, consisting of isolated case reports and small clinicopathologic studies compromised by the inclusion of both its more common and indolent counterpart, cutaneous LMS (atypical intradermal smooth muscle neoplasm), as well as highly aggressive deep-seated tumors. Thus, precise clinicopathologic characterization is limited. Cases of subcutaneous LMS reviewed at the University of Michigan and Cleveland Clinic from 1994 to 2022 were included in this retrospective study. A total of 39 cases were identified. The mean age was 61 years, and the cohort was predominantly male (23/39; 59%). Tumors averaged 4.2 cm and most commonly arose on the extremities (32/39; 82%). The majority (38/39; 97%) were diagnosed at an early pathologic stage (pT1 or pT2). Histopathologically, most tumors were well-circumscribed and were assigned a Fédération Nationale des Centers de Lutte Contre le Cancer grade of either 1 or 2 (24/39; 62%). The majority (22/39; 56%) appeared to arise in association with a blood vessel. Of the 36 cases with accessible clinical data and follow-up (mean 34 mo, range 0 to 94 mo), 12 (33%) were noted to have metastasized, with the lung representing the most common anatomic location. One case recurred locally. Six of 36 patients (17%) died from the disease at an average of 47 months after diagnosis (range 16 to 94 mo). Metastasis or death from disease was significantly associated with the Fédération Nationale des Centers de Lutte Contre le Cancer grade ( P =0.0015), the presence of necrosis ( P =0.032), tumor size ( P =0.049), and AJCC tumor stage ( P =0.036). These data demonstrate that subcutaneous LMS are more aggressive than dermal-based tumors and have a prognosis akin to that of deep-seated LMS.

The Role of Surgery in Oligometastatic Retroperitoneal Sarcoma

Retroperitoneal sarcomas are extremely rare, comprising <15% of primary sarcomas. Distant metastasis occurs in about 20% of cases, with pulmonary and hepatic metastasis as the most common sites of hematogenous spread. Although surgical resection is well established as the main treatment of localized primary disease, there are limited guidelines for the surgical treatment of intra-abdominal and distant metastases. There are inadequate systemic treatment options for patients with metastatic sarcoma, thereby necessitating the consideration of surgical options in carefully selected patients. Key points to consider include tumor biology, patient fitness and co-morbidities, overall prognosis, and goals of care. Multidisciplinary sarcoma tumor board discussion for each case is an essential practice in order to deliver the best care to these patients. The purpose of this review is to summarize the published literature on the past and present role of surgery in the treatment of oligometastatic retroperitoneal sarcoma in order to inform the management of this difficult disease.

WNT signaling in the tumor microenvironment promotes immunosuppression in murine pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is associated with activation of WNT signaling. Whether this signaling pathway regulates the tumor microenvironment has remained unexplored. Through single-cell RNA sequencing of human pancreatic cancer, we discovered that tumor-infiltrating CD4+ T cells express TCF7, encoding for the transcription factor TCF1. We conditionally inactivated Tcf7 in CD4 expressing T cells in a mouse model of pancreatic cancer and observed changes in the tumor immune microenvironment, including more CD8+ T cells and fewer regulatory T cells, but also compensatory upregulation of PD-L1. We then used a clinically available inhibitor of Porcupine, a key component of WNT signaling, and observed similar reprogramming of the immune response. WNT signaling inhibition has limited therapeutic window due to toxicity, and PD-L1 blockade has been ineffective in PDA. Here, we show that combination targeting reduces pancreatic cancer growth in an experimental model and might benefit the treatment of pancreatic cancer.

Factors associated with disease-free and abdominal recurrence-free survival in abdominopelvic and retroperitoneal sarcomas

Background and Objectives

Retroperitoneal and abdominopelvic sarcomas are rare heterogeneous malignancies. The only therapy proven to improve disease‐free survival (DFS) is R0/R1 surgical resection. We sought to analyze whether additional factors such as radiation and systemic therapy were associated with DFS and abdominal recurrence‐free survival (RFS).

Methods

Retrospective review of adults (≥18) with resectable abdominopelvic and retroperitoneal sarcomas who underwent intent‐to‐cure surgery at a high‐volume tertiary referral center between 1998 and 2015. The main outcome measures were DFS and abdominal RFS.

Results

Overall, 159 patients met the criteria for inclusion. Median follow‐up was 4.8 years (range 0.1–18.9 years). The most common histology was liposarcoma (49%). Systemic therapy was administered to 48% of patients and was not associated with improved outcomes. The neoadjuvant radiotherapy group (11%) had improved adjusted DFS (5.46 years, 95% CI [3.68, 7.24] vs. 3.1 years, 95% CI [2.48, 3.73]) and abdominal RFS (6.14 years, 95% CI [4.38, 7.89] vs. 3.22 years, 95% CI [2.61, 3.84]). The adjuvant radiotherapy group (19%) had no improvement.

Conclusions

In a cohort of patients undergoing resection for retroperitoneal or abdominopelvic sarcoma, neoadjuvant radiation improved DFS and abdominal RFS. A follow‐up of over three years was needed to appreciate a difference in outcomes.

A High-Content Screen for C/EBPα Expression Identifies Novel Therapeutic Agents in Dedifferentiated Liposarcoma

PURPOSE

Dedifferentiated liposarcoma (DDLS), one of the most common and aggressive sarcomas, infrequently responds to chemotherapy. DDLS survival and growth depend on underexpression of C/EBPα, a tumor suppressor and transcriptional regulator controlling adipogenesis. We sought to screen and prioritize candidate drugs that increase C/EBPα expression and may therefore serve as differentiation-based therapies for DDLS.

EXPERIMENTAL DESIGN

We screened known bioactive compounds for the ability to restore C/EBPα expression and inhibit proliferation selectively in two DDLS cell lines but not in normal adipose-derived stem cells (ASC). Selected hits' activity was validated, and the mechanism of the most potent, SN-38, was investigated. The in vivo efficacy of irinotecan, the prodrug of SN-38, was evaluated in DDLS xenograft models.

RESULTS

Of 3,119 compounds, screen criteria were met by 19. Validation experiments confirmed the DDLS selectivity of deguelin, emetine, and SN-38 and showed that they induce apoptosis in DDLS cells. SN-38 had the lowest IC₅₀ (approximately 10 nmol/L), and its pro-apoptotic effects were countered by knockdown of CEBPA but not of TP53. Irinotecan significantly inhibited tumor growth at well-tolerated doses, induced nuclear expression of C/EBPα, and inhibited HIF1α expression in DDLS patient-derived and cancer cell line xenograft models. In contrast, doxorubicin, the most common treatment for nonresectable DDLS, reduced tumor growth by 30% to 50% at a dose that caused weight loss.

CONCLUSIONS

This high-content screen revealed potential treatments for DDLS. These include irinotecan, which induces apoptosis of DDLS cells in a C/EBPα-dependent, p53-independent manner, and should be clinically evaluated in patients with advanced DDLS.

Resident memory CD8+ T cells in regional lymph nodes mediate immunity to metastatic melanoma

The nature of the anti-tumor immune response changes as primary tumors progress and metastasize. We investigated the role of resident memory (Trm) and circulating memory (Tcirm) cells in anti-tumor responses at metastatic locations using a mouse model of melanoma-associated vitiligo. We found that the transcriptional characteristics of tumor-specific CD8+ T cells were defined by the tissue of occupancy. Parabiosis revealed that tumor-specific Trm and Tcirm compartments persisted throughout visceral organs, but Trm cells dominated lymph nodes (LNs). Single-cell RNA-sequencing profiles of Trm cells in LN and skin were distinct, and T cell clonotypes that occupied both tissues were overwhelmingly maintained as Trm in LNs. Whereas Tcirm cells prevented melanoma growth in the lungs, Trm afforded long-lived protection against melanoma seeding in LNs. Expanded Trm populations were also present in melanoma-involved LNs from patients, and their transcriptional signature predicted better survival. Thus, tumor-specific Trm cells persist in LNs, restricting metastatic cancer.

Dendritic cells maintain anti-tumor immunity by positioning CD8 skin-resident memory T cells

Tissue-resident memory (T_RM) T cells are emerging as critical components of the immune response to cancer; yet, requirements for their ongoing function and maintenance remain unclear. APCs promote T_RM cell differentiation and re-activation but have not been implicated in sustaining T_RM cell responses. Here, we identified a novel role for dendritic cells in supporting T_RM to melanoma. We showed that CD8 T_RM cells remain in close proximity to dendritic cells in the skin. Depletion of CD11c⁺ cells results in rapid disaggregation and eventual loss of melanoma-specific T_RM cells. In addition, we determined that T_RM migration and/or persistence requires chemotaxis and adhesion mediated by the CXCR6/CXCL16 axis. The interaction between CXCR6-expressing T_RM cells and CXCL16-expressing APCs was found to be critical for sustaining T_RM cell-mediated tumor protection. These findings substantially expand our knowledge of APC functions in T_RM T-cell homeostasis and longevity.

Large intraperitoneal lipoleiomyoma in a pre-menopausal woman: a case report

Background

Lipoleiomyoma is a rare, benign variant of the commonplace uterine leiomyoma. Unlike leiomyoma, these tumors are composed of smooth muscle cells admixed with mature adipose tissue. While rare, they are most frequently identified in the uterus, but even more infrequently have been described in extrauterine locations.

Case presentation

We describe a case report of a 45-year-old woman with a history of in vitro fertilization pregnancy presenting 6 years later with abdominal distention and weight loss found to have a 30-cm intra-abdominal lipoleiomyoma. While cross-sectional imaging can narrow the differential diagnosis, histopathological analysis with stains positive for smooth muscle actin, desmin, and estrogen receptor, but negative for HMB-45 confirms the diagnosis of lipoleiomyoma. The large encapsulated tumor was resected en bloc. The patients post-operative course was uneventful and her symptoms resolved.

Conclusions

Lipoleiomyoma should be considered on the differential diagnosis in a woman with a large intra-abdominal mass. While considered benign, resection should be considered if the mass is symptomatic, and the diagnosis is unclear or there is a concern for malignancy.

Immunotherapy for Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive form of skin cancer which, while chemosensitive, has high rates of relapse and chemoresistance, limiting the impact of chemotherapy. An immunogenic tumor, the management of advanced MCC has changed dramatically with the introduction of checkpoint inhibitors. This review will focus on the impact of immunotherapy in unresectable and metastatic MCC, ongoing research in the adjuvant and neoadjuvant settings, and future directions of immune-based strategies for this challenging cancer.

Resident and circulating memory T cells persist for years in melanoma patients with durable responses to immunotherapy

While T-cell responses to cancer immunotherapy have been avidly studied, long-lived memory has been poorly characterized. In a cohort of metastatic melanoma survivors with exceptional responses to immunotherapy, we probed memory CD8+ T-cell responses across tissues, and across several years. Single-cell RNA sequencing revealed three subsets of resident memory T (TRM) cells shared between tumors and distant vitiligo-affected skin. Paired T-cell receptor sequencing further identified clonotypes in tumors that co-existed as TRM in skin and as effector memory T (TEM) cells in blood. Clonotypes that dispersed throughout tumor, skin, and blood preferentially expressed a IFNG / TNF-high signature, which had a strong prognostic value for melanoma patients. Remarkably, clonotypes from tumors were found in patient skin and blood up to nine years later, with skin maintaining the most focused tumor-associated clonal repertoire. These studies reveal that cancer survivors can maintain durable memory as functional, broadly-distributed TRM and TEM compartments.

Memory CD8+ T cell responses to cancer

Long-lived memory CD8⁺ T cells play important roles in tumor immunity. Studies over the past two decades have identified four subsets of memory CD8⁺ T cells - central, effector, stem-like, and tissue resident memory - that either circulate through blood, lymphoid and peripheral organs, or reside in tissues where cancers develop. In this article, we will review studies from both pre-clinical mouse models and human patients to summarize the phenotype, distribution and unique features of each memory subset, and highlight specific roles of each subset in anti-tumor immunity. Moreover, we will discuss how stem-cell like and resident memory CD8⁺ T cell subsets relate to exhausted tumor-infiltrating lymphocytes (TIL) populations. These studies reveal how memory CD8⁺ T cell subsets together orchestrate durable immunity to cancer.

What matters most: Randomized controlled trial of breast cancer surgery conversation aids across socioeconomic strata

Background

Women of lower socioeconomic status (SES) with early‐stage breast cancer are more likely to report poorer physician‐patient communication, lower satisfaction with surgery, lower involvement in decision making, and higher decision regret compared to women of higher SES. The objective of this study was to understand how to support women across socioeconomic strata in making breast cancer surgery choices.

Methods

We conducted a 3‐arm (Option Grid, Picture Option Grid, and usual care), multisite, randomized controlled superiority trial with surgeon‐level randomization. The Option Grid (text only) and Picture Option Grid (pictures plus text) conversation aids were evidence‐based summaries of available breast cancer surgery options on paper. Decision quality (primary outcome), treatment choice, treatment intention, shared decision making (SDM), anxiety, quality of life, decision regret, and coordination of care were measured from T0 (pre‐consultation) to T5 (1‐year after surgery.

Results

Sixteen surgeons saw 571 of 622 consented patients. Patients in the Picture Option Grid arm (n = 248) had higher knowledge (immediately after the visit [T2] and 1 week after surgery or within 2 weeks of the first postoperative visit [T3]), an improved decision process (T2 and T3), lower decision regret (T3), and more SDM (observed and self‐reported) compared to usual care (n = 257). Patients in the Option Grid arm (n = 66) had higher decision process scores (T2 and T3), better coordination of care (12 weeks after surgery or within 2 weeks of the second postoperative visit [T4]), and more observed SDM (during the surgical visit [T1]) compared to usual care arm. Subgroup analyses suggested that the Picture Option Grid had more impact among women of lower SES and health literacy. Neither intervention affected concordance, treatment choice, or anxiety.

Conclusions

Paper‐based conversation aids improved key outcomes over usual care. The Picture Option Grid had more impact among disadvantaged patients.

Lay Summary

The objective of this study was to understand how to help women with lower incomes or less formal education to make breast cancer surgery choices.

Compared with usual care, a conversation aid with pictures and text led to higher knowledge. It improved the decision process and shared decision making (SDM) and lowered decision regret. A text‐only conversation aid led to an improved decision process, more coordinated care, and higher SDM compared to usual care. The conversation aid with pictures was more helpful for women with lower income or less formal education.

Conversation aids with pictures and text helped women make better breast cancer surgery choices.

A paper‐based pictorial conversation aid (pictures plus text) is beneficial to all patients with early‐stage breast cancer and particularly to disadvantaged patients. Between‐surgeon variation suggests that the maximal impact of such interventions requires standardized physician training combined with these interventions.

The Landmark Series: Randomized Trials Examining Surgical Margins for Cutaneous Melanoma

Between 1980 and 2004, six randomized, controlled trials (RCTs) have been performed to evaluate the width of surgical margin excision for primary cutaneous melanoma and its influence on recurrence and survival. These trials have led to the current recommendation of not more than a 2-cm margin excision and have allowed reduced morbidity of surgery for primary melanoma. Long-term follow-up data has been published which has led to impactful knowledge of the natural history of this disease, yet controversy remains for 1- to 2-mm thickness melanomas. Interpretation of these trials must be done in light of them enrolling patients before the use of sentinel node biopsy and contemporary immunotherapy regimens. These RCTs as well as a contemporary, actively enrolling trial are summarized and discussed in this review.

A Randomized Prospective Trial of Supine MRI-Guided Versus Wire-Localized Lumpectomy for Breast Cancer

BACKGROUND

Wire-localized excision of non-palpable breast cancer is imprecise, resulting in positive margins 15-35% of the time.

METHODS

Women with a confirmed diagnosis of non-palpable invasive breast cancer (IBC) or ductal carcinoma in situ (DCIS) were randomized to a new technique using preoperative supine magnetic resonance imaging (MRI) with intraoperative optical scanning and tracking (MRI group) or wire-localized (WL group) partial mastectomy. The main outcome measure was the positive margin rate.

RESULTS

In this study, 138 patients were randomly assigned. Sixty-six percent had IBC and DCIS, 22% had IBC, and 12% had DCIS. There were no differences in patient or tumor characteristics between the groups. The proportion of patients with positive margins in the MRI-guided surgery group was half that observed in the WL group (12 vs. 23%; p = 0.08). The specimen volumes in the MRI and WL groups did not differ significantly (74 ± 33.9 mL vs. 69.8 ± 25.1 mL; p = 0.45). The pathologic tumor diameters were underestimated by 2 cm or more in 4% of the cases by MRI and in 9% of the cases by mammography. Positive margins were observed in 68% and 58% of the cases underestimated by 2 cm or more using MRI and mammography, respectively, and in 15% and 14% of the cases not underestimated using MRI and mammography, respectively.

CONCLUSIONS

A novel system using supine MRI images co-registered with intraoperative optical scanning and tracking enabled tumors to be resected with a trend toward a lower positive margin rate compared with wire-localized partial mastectomy. Margin positivity was more likely when imaging underestimated pathologic tumor size.

Meta-analysis of completion lymph node dissection in sentinel lymph node-positive melanoma

BACKGROUND

The role of completion lymph node dissection (CLND) in patients with sentinel lymph node (SLN)-positive melanoma continues to be debated. This systematic review and meta-analysis evaluated survival and recurrence rate in these patients who underwent CLND, compared with observation.

METHODS

A comprehensive MEDLINE and Embase database search was performed for cohort studies and RCTs published between January 2000 and June 2017 that assessed the outcomes of CLND compared with observation in patients with SLN-positive melanoma. The primary outcome was survival and the secondary outcome was recurrence rate. Studies were assessed for quality using the Cochrane risk-of-bias tool for RCTs and Newcastle-Ottawa Scale for cohort studies. Pooled relative risk or hazard ratio with 95 per cent confidence intervals were calculated for each outcome. The extent of heterogeneity between studies was assessed with the I² test. The protocol was registered in PROSPERO (CRD42017070152).

RESULTS

Fifteen studies (13 cohort studies with 7868 patients and 2 RCTs with 2228 patients) were identified for qualitative synthesis. Thirteen studies remained for quantitative meta-analysis. Survival was similar in patients who underwent CLND and those who were observed (risk ratio (RR) for death 0·85, 95 per cent c.i. 0·71 to 1·02). The recurrence rate was also similar (RR 0·91, 0·79 to 1·05).

CONCLUSION

Patients with SLN-positive melanoma do not have a significant benefit in survival or recurrence rate if they undergo CLND rather than observation.

Oncogenic BRAFV600E Governs Regulatory T-cell Recruitment during Melanoma Tumorigenesis

Regulatory T cells (Treg) are critical mediators of immunosuppression in established tumors, although little is known about their role in restraining immunosurveillance during tumorigenesis. Here, we employ an inducible autochthonous model of melanoma to investigate the earliest Treg and CD8 effector T-cell responses during oncogene-driven tumorigenesis. Induction of oncogenic BRAFV600E and loss of Pten in melanocytes led to localized accumulation of FoxP3+ Tregs, but not CD8 T cells, within 1 week of detectable increases in melanocyte differentiation antigen expression. Melanoma tumorigenesis elicited early expansion of shared tumor/self-antigen-specific, thymically derived Tregs in draining lymph nodes, and induced their subsequent recruitment to sites of tumorigenesis in the skin. Lymph node egress of tumor-activated Tregs was required for their C-C chemokine receptor 4 (Ccr4)-dependent homing to nascent tumor sites. Notably, BRAFV600E signaling controlled expression of Ccr4-cognate chemokines and governed recruitment of Tregs to tumor-induced skin sites. BRAFV600E expression alone in melanocytes resulted in nevus formation and associated Treg recruitment, indicating that BRAFV600E signaling is sufficient to recruit Tregs. Treg depletion liberated immunosurveillance, evidenced by CD8 T-cell responses against the tumor/self-antigen gp100, which was concurrent with the formation of microscopic neoplasia. These studies establish a novel role for BRAFV600E as a tumor cell-intrinsic mediator of immune evasion and underscore the critical early role of Treg-mediated suppression during autochthonous tumorigenesis.Significance: This work provides new insights into the mechanisms by which oncogenic pathways impact immune regulation in the nascent tumor microenvironment. Cancer Res; 78(17); 5038-49. ©2018 AACR.

VISTA expression on tumor-infiltrating inflammatory cells in primary cutaneous melanoma correlates with poor disease-specific survival

Adaptive immune responses contribute to the pathogenesis of melanoma by facilitating immune evasion. V-domain Ig suppressor of T-cell activation (VISTA) is a potent negative regulator of T-cell function and is expressed at high levels on monocytes, granulocytes, and macrophages, and at lower densities on T-cell populations within the tumor microenvironment. In this study, 85 primary melanoma specimens were selected from pathology tissue archives and immunohistochemically stained for CD3, PD-1, PD-L1, and VISTA. Pearson's correlation coefficients identified associations in expression between VISTA and myeloid infiltrate (r = 0.28, p = 0.009) and the density of PD-1+ inflammatory cells (r = 0.31, p = 0.005). The presence of VISTA was associated with a significantly worse disease-specific survival in univariate analysis (hazard ratio = 3.57, p = 0.005) and multivariate analysis (hazard ratio = 3.02, p = 0.02). Our findings show that VISTA expression is an independent negative prognostic factor in primary cutaneous melanoma and suggests its potential as an adjuvant immunotherapeutic intervention in the future.

A Patient-Specific 3D-Printed Form Accurately Transfers Supine MRI-Derived Tumor Localization Information to Guide Breast-Conserving Surgery

BACKGROUND

Wire-localized excision of nonpalpable breast cancer is imprecise, resulting in positive margins 25-30% of the time.

METHODS

Patients underwent preoperative supine magnetic resonance imaging (MRI). A radiologist outlined the tumor edges on consecutive images, creating a three-dimensional (3D) view of its location. Using 3D printing, a bra-like plastic form (the Breast Cancer Locator [BCL]) was fabricated, with features that allowed a surgeon to (1) mark the edges of the tumor on the breast surface; (2) inject blue dye into the breast 1 cm from the tumor edges; and (3) place a wire in the tumor at the time of surgery.

RESULTS

Nineteen patients with palpable cancers underwent partial mastectomy after placement of surgical cues using patient-specific BCLs. The cues were in place in <5 min and no adverse events occurred. The BCL accurately localized 18/19 cancers. In the 18 accurately localized cases, all 68 blue-dye injections were outside of the tumor edges. Median distance from the blue-dye center to the pathologic tumor edge was 1.4 cm, while distance from the blue dye to the tumor edge was <5 mm in 4% of injections, 0.5-2.0 cm in 72% of injections, and >2 cm in 24% of injections. Median distance from the tumor center to the BCL-localized wire and to the clip placed at the time of diagnosis was similar (0.49 vs. 0.73 cm) on specimen mammograms.

CONCLUSIONS

Information on breast cancer location and shape derived from a supine MRI can be transferred safely and accurately to patients in the operating room using a 3D-printed form.

Collagen quantification in breast tissue using a 12-wavelength near infrared spectral tomography (NIRST) system

A portable near infrared spectral tomography (NIRST) system was adapted for breast cancer detection and treatment monitoring with improved speed of acquisition for parallel 12 wavelengths of parallel frequency-domain (FD) and continuous-wavelength (CW) measurement. Using a novel gain adjustment scheme in the Photomultiplier Tube detectors (PMTs), the data acquisition time for simultaneous acquisition involving three FD and three CW wavelengths, has been reduced from 90 to 55 seconds, while signal variation was also reduced from 2.1% to 1.1%. Tomographic images of breast collagen content have been recovered for the first time, and image reconstruction approaches with and without collagen content included have been validated in simulation studies and normal subject exams. Simulations indicate that including collagen content into the reconstruction procedure can significantly reduce the overestimation in total hemoglobin, water and lipid by 8.9μM, 1.8% and 15.8%, respectively, and underestimates in oxygen saturation by 9.5%, given an average 10% background collagen content. A breast cancer patient with invasive ductal carcinoma was imaged and the reconstructed images show that the recovered tumor/background contrast in total hemoglobin increased from 1.5 to 1.7 when collagen was included in reconstruction.

Resident memory T cells in the skin mediate durable immunity to melanoma

Tissue-resident memory T (T_RM) cells have been widely characterized in infectious disease settings; however, their role in mediating immunity to cancer remains unknown. We report that skin-resident memory T cell responses to melanoma are generated naturally as a result of autoimmune vitiligo. Melanoma antigen-specific T_RM cells resided predominantly in melanocyte-depleted hair follicles and were maintained without recirculation or replenishment from the lymphoid compartment. These cells expressed CD103, CD69, and CLA (cutaneous lymphocyte antigen), but lacked PD-1 (programmed cell death protein-1) or LAG-3 (lymphocyte activation gene-3), and were capable of making IFN-γ (interferon-γ). CD103 expression on CD8 T cells was required for the establishment of T_RM cells in the skin but was dispensable for vitiligo development. CD103⁺ CD8 T_RM cells were critical for protection against melanoma rechallenge. This work establishes that CD103-dependent T_RM cells play a key role in perpetuating antitumor immunity.

Myeloid Cells That Impair Immunotherapy Are Restored in Melanomas with Acquired Resistance to BRAF Inhibitors

Acquired resistance to BRAFV600E inhibitors (BRAFi) in melanoma remains a common clinical obstacle, as is the case for any targeted drug therapy that can be developed given the plastic nature of cancers. Although there has been significant focus on the cancer cell-intrinsic properties of BRAFi resistance, the impact of BRAFi resistance on host immunity has not been explored. Here we provide preclinical evidence that resistance to BRAFi in an autochthonous mouse model of melanoma is associated with restoration of myeloid-derived suppressor cells (MDSC) in the tumor microenvironment, initially reduced by BRAFi treatment. In contrast to restoration of MDSCs, levels of T regulatory cells remained reduced in BRAFi-resistant tumors. Accordingly, tumor gene expression signatures specific for myeloid cell chemotaxis and homeostasis reappeared in BRAFi-resistant tumors. Notably, MDSC restoration relied upon MAPK pathway reactivation and downstream production of the myeloid attractant CCL2 in BRAFi-resistant melanoma cells. Strikingly, although combination checkpoint blockade (anti-CTLA-4 + anti-PD-1) was ineffective against BRAFi-resistant melanomas, the addition of MDSC depletion/blockade (anti-Gr-1 + CCR2 antagonist) prevented outgrowth of BRAFi-resistant tumors. Our results illustrate how extrinsic pathways of immunosuppression elaborated by melanoma cells dominate the tumor microenvironment and highlight the need to target extrinsic as well as intrinsic mechanisms of drug resistance. Cancer Res; 77(7); 1599-610. ©2017 AACR.

Frequent alterations and epigenetic silencing of differentiation pathway genes in structurally rearranged liposarcomas

We explored diverse alterations contributing to liposarcomagenesis by sequencing the genome, exome, transcriptome, and cytosine methylome of a primary and recurrent dedifferentiated liposarcoma (DLPS) from distinct chemotherapy/radiotherapy-naïve patients. The liposarcoma genomes had complex structural rearrangements, but in different patterns, and with varied effects on the structure and expression of affected genes. While the point mutation rate was modest, integrative analyses and additional screening identified somatic mutations in HDAC1 in 8.3% of DLPS. Liposarcoma methylomes revealed alterations in differentiation pathway genes, including CEBPA methylation in 24% of DLPS. Treatment with demethylating agents, which restored CEBPA expression in DLPS cells, was anti-proliferative and pro-apoptotic in vitro and reduced tumor growth in vivo. Both genetic and epigenetic abnormalities established a role for small RNAs in liposarcomagenesis, typified by methylation-induced silencing of microRNA-193b in DLPS but not its well-differentiated counterpart. These findings reveal an unanticipated role for epigenetic abnormalities in DLPS tumors and suggest demethylating agents as potential therapeutics.

SIGNIFICANCE

Multimodality sequence analysis of DLPS revealed recurrent mutations and epigenetic abnormalities critical to liposarcomagenesis and to the suppression of adipocyte differentiation. Pharmacologic inhibition of DNA methylation promoted apoptosis and differentiated DLPS cells in vitro and inhibited tumor growth in vivo, providing a rationale for investigating methylation inhibitors in this disease.

Expression profiling of liposarcoma yields a multigene predictor of patient outcome and identifies genes that contribute to liposarcomagenesis

Liposarcomas are the most common type of soft tissue sarcoma but their genetics are poorly defined. To identify genes that contribute to liposarcomagenesis and serve as prognostic candidates, we undertook expression profiling of 140 primary liposarcoma samples, which were randomly split into training set (n = 95) and test set (n = 45). A multigene predictor for distant recurrence-free survival (DRFS) was developed by the supervised principal component method. Expression levels of the 588 genes in the predictor were used to calculate a risk score for each patient. In validation of the predictor in the test set, patients with low risk score had a 3-year DRFS of 83% versus 45% for high risk score patients (P = 0.001). The HR for high versus low score, adjusted for histologic subtype, was 4.42 (95% CI, 1.26-15.55; P = 0.021). The concordance probability for risk score was 0.732. In contrast, the concordance probability for histologic subtype, which had been considered the best predictor of outcome in liposarcoma, was 0.669. Genes related to adipogenesis, DNA replication, mitosis, and spindle assembly checkpoint control were all highly represented in the multigene predictor. Three genes from the predictor, TOP2A, PTK7, and CHEK1, were found to be overexpressed in liposarcoma samples of all five subtypes and in liposarcoma cell lines. RNAi-mediated knockdown of these genes in liposarcoma cell lines reduced proliferation and invasiveness and increased apoptosis. Taken together, our findings identify genes that seem to be involved in liposarcomagenesis and have promise as therapeutic targets, and support the use of this multigene predictor to improve risk stratification for individual patients with liposarcoma.

Abstract 3100: The RNA-binding protein insulin-like growth factor 2 mRNA-binding protein 3 is oncogenic in liposarcoma

Introduction: The insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) is an oncofetal mRNA binding protein that controls migration and proliferation through post-transcriptional regulation of target genes. It is aberrantly expressed in various cancers. We sought to determine the alterations in IGF2BP3 expression and copy number in well-differentiated (WD) and dedifferentiated (DD) liposarcoma (LS) and elucidate its role in driving oncogenesis in WD and DD LS cell lines.

Methods: U133A microarray analysis was performed on 61 DD and 52 WD LS as well as 17 normal fat (NF) tissue samples. CGH Agilent arrays were used to determine IGF2BP3 amplification status. An shRNA lentiviral system was used to knockdown (KD) IGF2BP3 in DD (DDLS8817, LPS141) and WD (RWD3051) cell lines. Cell proliferation, apoptosis, and mRNA expression were analyzed by Cyquant, annexin V, and qRT-PCR, respectively.

Results: CGH analysis showed IGF2BP3 amplification in 19% of DDLS (n=36) and 5% of WDLS (n=36) tumor samples. On U133A analysis IGF2BP3 was 2.5-fold and 1.2-fold upregulated in DDLS and WDLS, respectively, compared to NF. IGF2BP3 was overexpressed in 49% of DDLS and 33% of WDLS tumor samples. Gene expression was increased in DDLS8817 (3-fold), LPS141 (6-fold) and RWD3051 (6-fold) compared to adipose-derived stem cells. IGF2BP3 KD reduced expression &gt;95%(p&lt;0.05) compared to empty vector control for each cell line. IGF2BP3 KD decreased proliferation by 43%, 31%, and 36%(p&lt;0.001) in DDLS8817, LPS141 and RWD3051, respectively, compared to control. Apoptosis was increased by 34%, 55%, and 58%(p&lt;0.0001) compared to control in DDLS8817, LPS141, and RWD3051, respectively, and correlated with level of IGF2BP3 upregulation. p27, a cell cycle inhibitor, was identified as a potential target of IGF2BP3 by photoreactive crosslinking and immunoprecipitation. On Western blot analysis p27 was increased, cyclin D1 was decreased, and p53 was decreased in IGF2BP3 KD compared to control in LPS141, consistent with the functional effects observed.

Conclusions: IGF2BP3 overexpression is essential for proliferation and survival of LS cells. The cell cycle regulator, p27 was identified as an IGF2BP3 target mediating these functional effects. Identification of additional IGF2BP3 targets may lead to new therapeutic options for patients with DD and WD liposarcoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3100.

Identification of a candidate regulatory element within the 5' flanking region of the mouse Igh locus defined by pro-B cell-specific hypersensitivity associated with binding of PU.1, Pax5, and E2A

The Igh locus is controlled by cis-acting elements, including Emu and the 3' IgH regulatory region which flank the C region genes within the well-studied 3' part of the locus. Although the presence of additional control elements has been postulated to regulate rearrangements of the VH gene array that extends to the 5' end of the locus, the 5' border of Igh and its flanking region have not been characterized. To facilitate the analysis of this unexplored region and to identify potential novel control elements, we physically mapped the most D-distal VH segments and scanned 46 kb of the immediate 5' flanking region for DNase I hypersensitive sites. Our studies revealed a cluster of hypersensitive sites 30 kb upstream of the most 5' VH gene. Detection of one site, HS1, is restricted to pro-B cell lines and HS1 is accessible to restriction enzyme digestion exclusively in normal pro-B cells, the stage defined by actively rearranging Igh-V loci. Sequence motifs within HS1 for PU.1, Pax5, and E2A bind these proteins in vitro and these factors are recruited to HS1 sequence only in pro-B cells. Transient transfection assays indicate that the Pax5 binding site is required for the repression of transcriptional activity of HS1-containing constructs. Thus, our characterization of the region 5' of the VH gene cluster demonstrated the presence of a single cluster of DNase I hypersensitive sites within the 5' flanking region, and identified a candidate Igh regulatory region defined by pro-B cell-specific hypersensitivity and interaction with factors implicated in regulating VDJ recombination.

Germline diversity of the expressed BALB/c VhJ558 gene family

Although the mouse immunoglobulin heavy chain (Igh) locus contains 15 heavy chain V (Vh) gene families, at least half of the Vh gene segments are members of the VhJ558 family. This large Vh gene family represents the least characterized germline coding regions of any of the mouse antigen receptor loci and the contribution of individual VhJ558 genes to the preimmune repertoire is poorly understood. In fact, relatively few germline VhJ558 sequences have been reported for BALB/c, the foundation strain for mouse immunoglobulin genetics and the prototypic strain of the Igh(a) haplotype. Here we present a database consisting of 66 sequences estimated to represent one-half of the total number of functional BALB/c VhJ558 genes. Our results indicate that a subset of the VhJ558 genes is highly expressed in the preimmune repertoire, with just nine Vh sequences accounting for nearly 50% of the VhJ558 heavy chains expressed by splenic B cells. We show that this disparity in the expressed Vh gene repertoire is not due to the position of the Vh genes relative to the Dh cluster or to multiple germline copies of the highly expressed VhJ558 genes. Together, these data constitute the first detailed analysis of functional BALB/c VhJ558 genes, demonstrate a striking bias in the use of particular VhJ558 genes in the preimmune repertoire, and provide sufficient information to study the regulation of the Dh-distal region of the Igh-V locus at the level of individual genes.