Identification of TRA-1-60-positive cells as a potent refractory population in follicular lymphomas

Pathological and Biological Significance of the Specific Glycan, TRA-1-60, on Aggressive Gastric Adenocarcinoma

The glycans form a unique complex on the surface of cancer cells and play a pivotal role in tumor progression, impacting proliferation, invasion, and metastasis. TRA-1-60 is a glycan that was identified as a critical marker for the establishment of fully reprogrammed inducible pluripotent stem cells. Its expression has been detected in multiple cancer tissues, including embryonal carcinoma, prostate cancer, and pancreatic cancer, but the biological and pathological characterization of TRA-1-60-expressing tumor cells remains unclear within various types of malignancies. Here, we report the biological characteristics of TRA-1-60-expressing gastric cancer cells, especially those with its cell surface expression, and the therapeutic significance of targeting TRA-1-60. The cells with cell membrane expression of TRA-1-60 were mainly observed in the invasive area of patient gastric cancer tissues and correlated with advanced stages of the disease based on histopathological and clinicopathological analyses. In vitro analysis using a scirrhous gastric adenocarcinoma line, HSC-58, which highly expresses TRA-1-60 on its plasma membrane, revealed increased stress-resistant mechanisms, supported by the upregulation of glutathione synthetase and NCF-1 (p47phox) via lipid-ROS regulatory pathways, as detected by RNA-seq analysis followed by oxidative stress gene profiling. Our in vivo therapeutic study using the TRA-1-60-targeting antibody-drug conjugate, namely, Bstrongomab-conjugated monomethyl auristatin E, showed robust efficacy in a mouse model of peritoneal carcinomatosis induced by intraperitoneal xenograft of HSC-58, by markedly reducing massive tumor ascites. Thus, targeting the specific cell surface glycan, TRA-1-60, shows a significant therapeutic impact in advanced-stage gastric cancers.

T-cell receptor gamma gene rearrangement analysis of classic Hodgkin lymphoma using a BIOMED-2 assay: a paraffin-embedded tissue analysis of one hundred cases

In the new WHO classifications of haematolymphoid tumours (WHO-HAEM5), classic Hodgkin lymphoma (cHL) is categorized into B-cell lymphoid proliferations and lymphomas. Although the majority of Hodgkin Reed-Sternberg (HRS) cells are of germinal center B-cell origin with some defects of B-cell transcription factors, they rarely express T-cell antigens or cytotoxic molecules. Clonality analyses on cHL samples using BIOMED-2 have been reported by several groups; however, those studies were only focused on Ig regions, including IgH, Ig-kappa, and Ig-lambda, and TCR-γ clonality analysis of cHL has not yet been explored. Here, we investigated TCR-γ gene rearrangement for one hundred cases using a PCR-based method. Four of one hundred (4%) cases showed TCR-γ clonal peaks. Of these, three were at an advanced stage and one patient died of the disease. To clarify whether HRS cells showed T-cell clonality or not, we performed PCR analysis using DNAs of microdissected HRS cells. Three samples showed identical clonal peaks with bulk specimens. Our results indicate that cHL is a heterogeneous disease of mainly B-cell and rarely T-cell origin with a special phenotype. Further molecular studies are warranted.

Selective ablation of TRA-1-60+ pluripotent stem cells suppresses tumor growth of prostate cancer

Purpose: TRA-1-60 (TRA) is an established transcription factor of embryonic signaling and a well-known marker of pluripotency. It has been implicated in tumorigenesis and metastases, is not expressed in differentiated cells, which makes it an appealing biomarker for immunopositron emission tomography (immunoPET) imaging and radiopharmaceutical therapy (RPT). Herein, we explored the clinical implications of TRA in prostate cancer (PCa), examined the potential of TRA-targeted PET to specifically image TRA+ cancer stem cells (CSCs) and assessed response to the selective ablation of PCa CSCs using TRA-targeted RPT. Experimental Design: First, we assessed the relationship between TRA (PODXL) copy number alterations (CNA) and survival using publicly available patient databases. The anti-TRA antibody, Bstrongomab, was radiolabeled with Zr-89 or Lu-177 for immunoPET imaging and RPT in PCa xenografts. Radiosensitive tissues were collected to assess radiotoxicity while excised tumors were examined for pathologic treatment response. Results: Patients with tumors having high PODXL CNA exhibited poorer progression-free survival than those with low PODXL, suggesting that it plays an important role in tumor aggressiveness. TRA-targeted immunoPET imaging specifically imaged CSCs in DU-145 xenografts. Tumors treated with TRA RPT exhibited delayed growth and decreased proliferative activity, marked by Ki-67 immunohistochemistry. Aside from minor weight loss in select animals, no significant signs of radiotoxicity were observed in the kidneys or livers. Conclusions: We successfully demonstrated the clinical significance of TRA expression in human PCa, engineered and tested radiotheranostic agents to image and treat TRA+ prostate CSCs. Ablation of TRA+ CSCs blunted PCa growth. Future studies combining CSC ablation with standard treatment will be explored to achieve durable responses.

Detecting TRA-1-60 in Cancer via a Novel Zr-89 Labeled ImmunoPET Imaging Agent

TRA-1-60 (TRA) is a cell-surface antigen implicated in drug resistance, relapse, and recurrence. Its expression has been reported in breast, prostate, pancreatic, ovarian tumors, and follicular lymphoma, which paved the development of the therapeutic antibody, Bstrongomab (Bsg), and its drug conjugates. Because patient selection is critical to achieve clinical benefit, a noninvasive imaging agent to select TRA+ lesions in patients is needed. Herein, we report the development of the immunopositron emission tomography (immunoPET) radiotracer ⁸⁹Zr-radiolabeled Bsg and its potential to delineate TRA+ tumors. Bsg was conjugated to the bifunctional chelator desferrioxamine (DFO) and radiolabeled with [⁸⁹Zr]Zr-oxalate. [⁸⁹Zr]Zr-DFO-Bsg was characterized in vitro and evaluated in vivo for uptake and specificity in high and low TRA-expressing BxPC-3 pancreatic and PC-3 prostate cancer models, respectively. Uptake was compared against [⁸⁹Zr]Zr-DFO-IgG, a nonspecific control radiotracer. Immunohistochemical (IHC) staining of patient cancer tissues using Bsg was performed to explore its clinical significance. A specific activity of 0.18 ± 0.01 GBq/mg (4.8 ± 0.3 mCi/mg) was obtained for [⁸⁹Zr]Zr-DFO-Bsg. BxPC-3 xenografts exhibited three-fold higher radiotracer uptake compared to [⁸⁹Zr]Zr-DFO-IgG. Competitive saturation studies using BxPC-3 xenografts further confirmed tracer specificity. The TRA-specific probe had lower accumulation in PC-3 xenografts. Ex vivo autoradiographs correlated with TRA expression from the histopathology of the resected tumor xenografts. Additionally, patient cancer tissues demonstrated positive staining with Bsg with metastatic lesions exhibiting the highest staining. This study demonstrates the potential of [⁸⁹Zr]Zr-DFO-Bsg as an imaging agent for noninvasive detection of TRA+ tumors.

PODXL1 promotes metastasis of the pancreatic ductal adenocarcinoma by activating the C5aR/C5a axis from the tumor microenvironment

Pancreatic invasive ductal adenocarcinoma (PDAC) is a representative intractable malignancy under the current cancer therapies, and is considered a scirrhous carcinoma because it develops dense stroma. Both PODXL1, a member of CD34 family molecules, and C5aR, a critical cell motility inducer, have gained recent attention, as their expression was reported to correlate with poor prognosis for patients with diverse origins including PDAC; however, previous studies reported independently on their respective biological significance. Here we demonstrate that PODXL1 is essential for metastasis of PDAC cells through its specific interaction with C5aR. In vitro assay demonstrated that PODXL1 bound to C5aR, which stabilized C5aR protein and recruited it to cancer cell plasma membranes to receive C5a, an inflammatory chemoattractant factor. PODXL1 knockout in PDAC cells abrogated their metastatic property in vivo, emulating the liver metastatic mouse model treated with anti-C5a neutralizing antibody. In molecular studies, PODXL1 triggered EMT on PDAC cells in response to stimulation by C5a, corroborating PODXL1 involvement in PDAC cellular invasive properties via specific interaction with the C5aR/C5a axis. Confirming the molecular assays, histological examination showed coexpression of PODXL1 and C5aR at the invasive front of primary cancer nests as well as in liver metastatic foci of PDAC both in the mouse metastasis model and patient tissues. Hence, the novel direct interaction between PODXL1 and the C5aR/C5a axis may provide a better integrated understanding of PDAC biological characteristics including its tumor microenvironment factors.

Identification of TRA-1-60-positive cells as a potent refractory population in follicular lymphomas

Despite receiving rituximab‐combined chemotherapy, follicular lymphoma (FL) patients often suffer tumor recurrence and understand that the cause of relapse in FL would thus significantly ameliorate the tumor therapeutics. In the present study, we show that TRA‐1‐60‐expressing cells are a unique population in FL, converge to the conventional stem cell marker Oct3/4 and ALDH1‐positive population, and resist current B‐lymphoma agents. TRA‐1‐60 expression was observed in scattered lymphoma cells in FL tissues only as well as in resting B‐lymphocytes inside germinal centers. Retrospective comparison between recurrent and cognate primary tissues showed that the number of TRA‐1‐60‐positive cells from rituximab, cyclophosphamide, hydroxydaunorubicin, vincristine, and prednisone (R‐CHOP)‐treated FL had increased relative to primary tissue, a finding corroborated by assays on different rituximab‐treated FL cell lines, FL‐18 and DOHH2, wherein TRA‐positive cell numbers increased over 10‐fold compared to the untreated sample. Concordantly, scanty TRA‐1‐60‐positive FL‐18 cells implanted s.c. into mice evinced potent tumor‐initiating capacity in vivo, where tumors were 12‐fold larger in volume (P = 0.0021 < 0.005) and 13‐fold heavier in weight (P = 0.0015 < 0.005) compared to those xenografted from TRA‐negative cells. To explain these results, gene expression profiling and qPCR analysis indicated that TRA‐1‐60‐positive cells defined a distinct population from that of TRA‐negative cells, with upregulation of multiple drug transporters and therapeutic resistance genes. Hence, TRA‐1‐60‐expressing cells in FL are considered to be vigorously intractable against conventional therapeutic agents, which may explain its refractory recurrence.