Abstract 3974: Investigating doxorubicin resistance in fibrosarcoma

Cytotoxic chemotherapy has been the backbone of medical oncology for nearly a century for multiple cancer types. However, when treating advanced or metastatic disease toxicity, side effects, and acquired resistance often limit the duration of therapy. While randomized control trials have traditionally served as the proving ground for first and subsequent line therapies, rare tumor subtypes including soft tumor sarcoma (STS) provide unique challenges for developing robust treatment data. By developing human based in vitro models, we can investigate potential therapeutic mechanisms for STS. Fibrosarcoma is one distinct histologic STS subtype that relies heavily on anthracycline treatment in the first line setting, however, there are limited options once resistance develops. Anthracyclines, including doxorubicin, exert their effect through a variety of mechanisms including reactive oxygen species, DNA-adduct formation, and inhibiting topoisomerase II, histone eviction, calcium and iron homeostasis, and ceramide overproduction. However, there have also been multiple mechanisms of doxorubicin resistance including disruption of cell membrane, alteration of cell surface molecules, inactivation of drugs, gene amplification, activating alternative signaling pathways, and affecting cellular repair mechanisms. In order to investigate the role of anthracycline resistance in fibrosarcoma lines we acquired two human derived fibrosarcoma lines SW684 and HT-1080 from American Type Culture Collection (ATCC). Characterization of HT-1080 using publicly available datasets demonstrated that TP53, CDK2NA and NF1 serve as major driver mutations while SW684 relies on NRAS and IDH1 mutations. We further characterized these cell lines in vitro and noted that HT-1080 has a quick doubling time of 16 hours while SW684 has a doubling time of 91 hours. Additionally, after doxorubicin treatment, we found that HT-1080 is sensitive with an IC50 of 5.594 nanomolar while SW684 is relatively doxorubicin resistant with an IC50 of 28.915 micromolar. While proliferative rate may play a role in the sensitivities of these cell lines further characterization of the mechanism leading to doxorubicin resistance is needed. To that end, we are using a CRISPR-Cas9 approach for further genome wide screening of these fibrosarcoma lines in the presence of doxorubicin. Exploring the genetic mechanisms that result in development of doxorubicin resistance may reveal novel, targetable mechanisms expanding treatment durability in this rare STS.

Citation Format: Rodney Dixon Dorand, Donna Dang, Elizabeth J. Davis, Ben Ho Park. Investigating doxorubicin resistance in fibrosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3974.

A multicenter evaluation of treatment patterns and outcomes for Adamantinoma-like Ewing sarcoma

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Background: Sarcomas are a rare and heterogenous group of malignancies comprised of > 150 histologic subtypes. Adamantinoma-like Ewing sarcoma (ALES) is a rare, small round blue cell tumor that represents a variant of Ewing sarcoma (EWS). First described 20 years ago, ALES harbors a EWS subset defining EWS-related translocation; however, ALES has a complex epithelial differentiation component defining it as a distinct clinical entity. Most ALES cases arise in the head and neck, but it has also been reported in the extremities and thorax. Given the rarity of ALES, there is a paucity of literature to guide treatment and describe outcomes. Methods: We performed a retrospective review (January 1, 2010-January 1, 2022) at two sarcoma centers in the United States and identified 4 cases of ALES. Tumor and patient characteristics were described, and patient outcomes were assessed. Results: Four patients were identified. 3 (75%) were male. Median age at diagnosis was 37 years (range 23-57). Primary site of ALES was head and neck (50%) and thorax (50%). Median tumor size was 4 cm (2.7-5.5 cm). All patients underwent resection of their primary tumor, and two (50%)received adjuvant radiation therapy. All pts received/are receiving adjuvant chemotherapy. 75% of patients were treated with Vincristine, Doxorubicin, and Cyclophosphane (VDC) alternating with Ifosfamide & Etoposide (IE) for 12-14 cycles. One patient received 4 cycles of adjuvant carboplatin and etoposide and radiation after an initial diagnosis of basaloid carcinoma but recurred 47 months later and diagnosed at ALES at that time. That patient underwent re-resection followed by adjuvant chemotherapy with Vincristine, Doxorubicin, and Ifosfamide (VAI). Median follow-up from initial diagnosis was 25 months (3-39 months). All patients are alive with no evidence of disease. Conclusions: Similar to treatment of EWS, a multidisciplinary strategy is paramount. VDC/IE is a reasonable treatment strategy. Further multicenter collaboration is essential to define clinical characterization of this rare sarcoma subtype and to guide treatment particularly in the relapsed or refractory setting.[Table: see text]

Efficacy of liposomal doxorubicin in patients with intra- and extra-abdominal desmoid fibromatosis

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Background: Desmoid tumors (DT) or aggressive fibromatosis are rare growths of fibroblastic connective tissue that can be locally aggressive but without metastatic potential. Most cases are sporadic, but 5-20% of cases are associated with Familial adenomatous polyposis (FAP). Despite numerous systemic options, optimal choice is unclear, and there is a paucity of studies comparing efficacy based on tumor site. Liposomal doxorubicin (LD) can be an appealing option for DT patients (pts) given its favorable schedule and toxicity profile. In this study, we compared outcomes in pts with intra-abdominal (IA) and extra-abdominal (EA) DT who received LD. Methods: We identified pts with DT who were treated with LD between 1/2010 - and 2/2022 at two sarcoma centers. Tumor and pt characteristics and outcomes were clinically (symptom improvement) and radiologically (RECIST 1.1) assessed. Results: 40 pts with DT treated with LD were identified; 58% female and 42% male. Pt characteristics and outcomes are summarized in Table 1. Primary tumor site was IA in 21 (53%) pts. FAP was present more commonly in pts with IA vs EA DT, 8/21 (43%) and 4/19 (21%), respectively. In the IA cohort, LD was given as first (15/21, 71%), second (10%) or third (19%) line therapy. LD was used more commonly as a later line in the EA cohort with 16%, 52%, 16%, and 16% receiving it in first, second, third, and fourth lines, respectively. 37 pts were evaluable for response. Response rate in the IA cohort treated in first-line was 50% (8 of 16) and 10 of 12 evaluable pts had symptomatic improvement. No first-line responses were seen in the EA cohort. As later lines of therapy, 7/12 pts had disease control in the second line, 6/8 pts in the third line, and 1/2 pts in the fourth line with LD in the IA cohort. 1 patient had fourth line response to LD in the EA cohort. Disease control rate with LD was 72.5% across all pts. Reasons for early discontinuation of LD included progression or lack of symptom improvement (20%), allergic reaction (12.5%), adverse effects (7.5%), or infection (2.5%). No acute or long-term cardiotoxicity was reported. 2 pts had no signs of recurrence or symptoms at follow-up, 33 pts were alive with symptomatic DT, 1 patient died from disease, and 3 were lost to follow-up. Conclusions: In our study, LD provided tumor response, disease control, and symptomatic improvement regardless of location or prior therapy, with responses most frequently seen in IA DT in first line setting. Further studies should include comparison of efficacy, adverse effects, and patient-reported outcomes while accounting for tumor location and line of therapy. [Table: see text]

The efficacy of PD-L1 blockade on PD-L1 negative medulloblastoma is dependent on timing and the tumor microenvironment

PD-L1 blockade has shown great success in the rejection of specific PD-L1+ tumor-types within various tissues. Blocking PD-L1 interactions with PD-1 molecules expressed on effector T cells allow them to engage their targets unimpeded and enhances tumor rejections. However, most pediatric tumors and some adult tumors express low to no surface PD-L1. Interestingly, some reports have demonstrated the rejection of PD-L1 negative tumors after treatment with anti-PD-L1 antibodies (Abs). When we administered anti-PD-L1 Abs 7 days after injection of CRISPR-negative PD-L1 (crPD-L1neg) medulloblastoma (MM1) tumors, all tumors were rejected. However, treating with anti-PD-L1 Abs at the time of tumor inoculation (day 0), resulted in a greatly diminished response to further treatment and a loss of protection. In addition, analysis of day 7 treated tumors in comparison to isotype and day 0 treated tumors, revealed an ~4- and ~2-fold increase in PD-1+ CD8+ T cells by day 21, respectively. These data suggest that the efficacy of anti-PD-L1 Abs on PD-L1 negative tumors is dependent on the timing and the microenvironment in which the T cell priming occurs. Our lab is investigating this phenomenon by interrogating the interaction of DC-T cell priming in the tumor draining lymph nodes (TDLNs) during the early stages of tumor growth. These studies may lead to improved efficacy of immune checkpoint blockade in PD-L1 negative tumors.

Brain Slice Culture Demonstrates Expedited Cell Traficking in the Presence of Fractalkine in a Medulloblastoma Tumor Microenvironment Model

20% of childhood brain tumors are medulloblastomas (MB), and the five-year survival rate can be as low as 60%. The interaction between MB and native immune cells are not well understood, and identifying methods of crosstalk could produce better outcomes for patients. Fractalkine (FKN) is a ligand for the receptor CX3CR1 that plays an inhibitory role in the brain’s immune system by keeping microglia quiescent. Normally, FKN is surface bound and expressed by neurons and astrocytes, but under inflammatory conditions FKN is secreted to serve as a chemoattractant. Preliminary work in our lab shows that FKN is produced by MB and may act as a decoy to maintain microglial quiescence leading to immune escape. Therefore we investigated FKN signaling and microglial kinetics ex vivo utilizing organotypic brain slice culture coupled with real time 2-photon laser scanning microscopy. To differentiate microglia from MB, CX3CR1+/GFP or CX3CR1GFP/GFP knock-in mice were sacrificed, and the brain was removed and sectioned. Slices were collected and cultured on inserts in an incubation chamber during imaging. To determine baseline activity, CX3CR1+/GFP and CX3CR1GFP/GFP brain slices were imaged over 48 hours. MB tumor cells, labelled with SNARF-1, were added to the cultures and imaged over the same time course. Images were processed to differentiate the motility of microglia and tumors. We found that microglia from CX3CR1+/GFP moved slower than microglia from CX3CR1GFP/GFP at baseline and in the presence of tumor. Furthermore, we found that MB moved faster in CX3CR1GFP/GFP slices, suggesting that fractalkine plays a role in the migration of MB.

Abstract B158: Cyclin dependent kinase-5 regulates IFNγ induced PD-L1 expression via IRF-1 in medulloblastoma

Immune checkpoint blockade offers an exciting, new adjuvant therapy to both solid and liquid tumors. However, the underlying mechanisms by which tumors alter their expression of immune checkpoint blockade ligands, such as programmed death ligand 1 (PD-L1), to achieve adaptive immune resistance needs to be further studied. We sought to investigate the mechanisms by which PD-L1 expression is regulated in response to IFNγ stimulation in medulloblastoma, a primary CNS neoplasm. MB is the most common pediatric CNS malignancy that is capable of metastasis to distant sites. MB is classified into four different molecular subgroups. Patched (PTCH), a signaling molecule of the Sonic Hedgehog (SHH) pathway, represents one subgroup and accounts for 25% of all sporadic human MB. Because MB develops from primitive cerebellar granule neuron precursor cells, it is thought that errors in development or migration of these neurons contribute to tumorigenesis. Cyclin Dependent Kinase 5 (CDK5) is a non-canonical member of the CDK family that does not require cyclin for activity but relies on binding to its obligate activators, p35 and p39 which are mostly expressed in post mitotic neurons. CDK5 is required for normal Central Nervous System (CNS) development.

Utilizing both short hairpin RNA (shRNA) approach and the bacterial CRISPR-Cas9 (Cr) system we silenced Cdk5 expression in a C57BL/6 (B6) syngeneic MB line derived from p53-/- PTCH+/- (MM1). In vitro proliferation experiments revealed that MM1-WT, MM1 cells transduced with shRNA targeting CDK5 (MM1-shCDK5), and MM1 cells transduced with non-silencing, scrambled RNA sequences (MM1-shNS) had similar growth kinetics. Since there were no intrinsic differences in in vitro growth kinetics, we subcutaneously injected immunocompetent C57BL/B6 mice with 5x104 tumor cells and measured tumor growth every three days. In our first experiment, 19 days after injection 7.7% (N=13) of mice injected with MM1-WT and 0% (N=7) injected with MM1-shNS were tumor free compared with 76.5% (N=13) of animals injected with MM1-shCDK5 Comparison of tumor free survival revealed statistically significant differences between the MM1-WT with MM1-shCDK5 groups (p <0.001) and MM1-shNS with MM1-shCDK5 (p <0.001). There was no significant difference between MM1-WT and MM1-shNS (p= 0.206). Furthermore, when injected into athymic Nu/Nu mice, MM1-WT and MM1-shCDK5 had similar subcutaneous growth kinetics. Therefore, we sought to interrogate the role of the immune system in enhanced killing of MM1-shCDK5 tumors. When exposed to IFNγ stimulation in vitro, genetic profiling of MM1-shCDK5 revealed a decrease in PD-L1 expression, a known immune checkpoint surface molecule, compared to MM1-WT. Assessing the downstream molecules that could account for differential IFNγ signaling, we found that upon stimulation of MM1-WT cells in vitro with 100ng/mL of recombinant murine IFNγ, interferon regulatory factor-1 (IRF-1) had a time dependent upregulation that corresponded with augmented cell surface expression of PD-L1. In IFNγ stimulated MM1-shCDK5 cells and MM1 transduced with Cr constructs targeting CDK5 (MM1-crCDK5), IRF-1 protein did not increase and corresponded with an absence of PD-L1 cell surface expression.

In summary, we have shown that Cdk5 is expressed in Type 2 MB and that silencing of its expression with shRNA results in an altered growth phenotype in vivo but not in vitro. Furthermore, eliminating the ability of MM1 tumors to express PD-L1 might lead to effective immune rejection of MM1-shCDK5. Mechanistically, we showed that this enhanced tumor rejection may be due in part to the failure of Cdk5 deficient MB cells to alter IRF-1 expression which serves as a transcription factor for PD-L1. These novel findings point to CDK5 as a potential immunotherapeutic target in MB.

Citation Format: Rodney Dixon Dorand, Jr., Agne Petrosiute, Joseph Nthale, Tej Pareek, Francesca Scrimieri, Jay Myers, Deborah Barkauskas, John J. Letterio, Duncan S. Stearns, Alex Y. Huang. Cyclin dependent kinase-5 regulates IFNγ induced PD-L1 expression via IRF-1 in medulloblastoma. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B158.

Confirmation of proximal 1q duplication using fluorescence in situ hybridization

We report on a boy with excessively wrinkled skin, mild micro/brachycephaly with mild hydrocephalus and slightly small temporal lobes, apparently low-set ears, retro/micrognathia and cleft soft palate (Pierre-Robin anomaly), patent ductus arteriosus and foramen ovale, pulmonary hypoplasia, eventration of the left hemidiaphragm, right cryptorchidism, a sacral dimple, flexion contractures of fingers and knees, and equinovarus deformities of both feet. The infant had a de novo dir dup(1)(pter-->q25::q12-->qter). Partial duplications involving proximal 1q have rarely been reported. Furthermore, this is the first case of proximal duplication of chromosome 1q with unequivocal identification using fluorescence in situ hybridization (FISH) with a chromosome 1 painting probe.

Rickets in premature infants fed different formulas

To study the role of formula as a cause of rickets, we randomly assigned 46 very-low-birth-weight (VLBW) infants (less than or equal to 1,500 gm) to one of three groups receiving either Isomil, a soy isolate formula, Similac with Iron, a common milk-based formula, or Similac 24 LBW, a hypercaloric milk-based formula designed for low-birth-weight infants during the first three to four months of life. Postnatal changes in serum calcium, phosphorus, alkaline phosphatase, and albumin were monitored during this study. Radiologic diagnosis of rickets was made in 60% of infants fed Isomil and 5% fed Similac with Iron. Significantly low levels of serum phosphorus and high levels of serum alkaline phosphatase were also seen in infants fed Isomil. The exact cause of the biochemical changes and the high incidence of rickets among infants fed Isomil is not clear. Poor solubility and possibly the decreased bioavailability of minerals in soy isolate formula may be important. We conclude that rickets occurs with high frequency among VLBW infants fed soy isolate, but not milk-based formulas. We suggest that prolonged feeding of soy isolate formulas should be avoided in VLBW infants.

Incidence of sepsis in neonates with clinical respiratory distress

Respiratory distress is the most frequent symptom initiating referral to neonatal intensive care centers. Previous reports have indicated that 40% of infants with sepsis proved by blood culture had respiratory symptoms as their clinical presentation. In this prospective study there were 145 consecutive infants referred because of respiratory distress. Two-site blood cultures were collated with all other clinical and laboratory data to confirm a diagnosis of septicemia. There was a 4.8% incidence of bacteremia, and clinical and laboratory parameters confirmed septicemia in 3.5% of infants studied. Sixty percent of these infants had group B streptococcal sepsis, and 80% had leukopenia. The low incidence of confirmed septicemia in infants referred because of respiratory distress suggests that antibiotic therapy should not be routine.

Phencyclidine ingestion: therapy review

The case of a 2 1/2-year-old comatose white boy successfully treated for acute phencyclidine poisoning has been reported with a brief review of symptoms and therapy. Supportive treatment consisted of maintaining intravascular volume; giving diuretics as needed to insure an adequate urinary output; controlling excessive secretions and seizure activity; and providing respiratory support. The patient recovered over a ten-day period of treatment without neurologic or psychologic sequelae.