Report of case series: Correlation between pathological and radiological evaluation and clinical course of three cases of metastatic renal cell carcinoma with cytoreductive nephrectomy after combined immuno-oncology therapy.

Introduction: The pathologic evaluation and clinical course of cytoreductive nephrectomy after combined immuno-oncology therapy were reviewed to understand the benefits of cytoreductive nephrectomy. Case presentation: Three patients with clear cell carcinoma underwent tumor biopsy before combined immuno-oncology therapy. Case 1 was found to have a sarcomatoid component upon nephrectomy and continued with combined immuno-oncology therapy. Case 2 discontinued combined immuno-oncology therapy due to adverse events but maintained tumor shrinkage. The patient was found to have viable cells in most nephrectomy specimens but has had no recurrence after combined immuno-oncology therapy was discontinued. In case 3, the residual tumor was deemed resectable with combined immuno-oncology therapy, and nephrectomy and metastasectomy were performed. No viable cells were observed in either specimen, and the patient has had no recurrence. Conclusion: Cytoreductive nephrectomy after combined immuno-oncology therapy may be useful to allow pathologic evaluation of treatment and provide an indicator for subsequent treatment.

Integrative genomic and transcriptomic profiling of pulmonary sarcomatoid carcinoma identifies molecular subtypes associated with distinct immune features and clinical outcomes.

Background: Pulmonary sarcomatoid carcinoma (PSC) is a rare and aggressive subtype of non-small cell lung cancer (NSCLC), characterized by the presence of epithelial and sarcoma-like components. The molecular and immune landscape of PSC has not been well defined. Methods: Multiomics profiling of 21 pairs of PSCs with matched normal lung tissues was performed through targeted high-depth DNA panel, whole-exome, and RNA sequencing. We describe molecular and immune features that define subgroups of PSC with disparate genomic and immunogenic features as well as distinct clinical outcomes. Results: In total, 27 canonical cancer gene mutations were identified, with TP53 the most frequently mutated gene, followed by KRAS. Interestingly, most TP53 and KRAS mutations were earlier genomic events mapped to the trunks of the tumors, suggesting branching evolution in most PSC tumors. We identified two distinct molecular subtypes of PSC, driven primarily by immune infiltration and signaling. The Immune High (IM-H) subtype was associated with superior survival, highlighting the impact of immune infiltration on the biological and clinical features of localized PSCs. Conclusions: We provided detailed insight into the mutational landscape of PSC and identified two molecular subtypes associated with prognosis. IM-H tumors were associated with favorable recurrence-free survival and overall survival, highlighting the importance of tumor immune infiltration in the biological and clinical features of PSCs.

USP9X inhibits metastasis in pulmonary sarcomatoid carcinoma by regulating epithelial-mesenchymal transition, angiogenesis and immune infiltration.

BACKGROUND: Pulmonary sarcomatoid carcinoma (PSC) is a highly invasive pulmonary malignancy with an extremely poor prognosis. The results of previous studies suggest that ubiquitin-specific peptidase 9X (USP9X) contributes to the progression of numerous types of cancer. Nevertheless, there is little knowledge about the molecular mechanisms and functions of USP9X in the metastasis of PSC. METHODS: Immunohistochemistry and western blotting were used to detect USP9X expression levels in PSC tissues and cells. Wound healing, transwell, enzyme-linked immunosorbent assay (ELISA), tube formation, and aortic ring assays were used to examine the function and mechanism of USP9X in the metastasis of PSC. RESULTS: Expression of USP9X was markedly decreased and significantly correlated with metastasis and prognosis of patients with PSC. Then we revealed that USP9X protein levels were negatively associated with the levels of epithelial-mesenchymal transition (EMT) markers and the migration of PSC cells. It was confirmed that USP9X in PSC cells reduced VEGF secretion and inhibited tubule formation of human umbilical vein endothelial cells (HUVEC) in vitro. USP9X was detected to downregulate MMP9. Meanwhile, MMP9 was positively related to EMT, angiogenesis and was negatively related to immune infiltration in the public databases. USP9X was significantly negatively associated with the expression of MMP9, EMT markers, CD31, and positively associated with CD4, and CD8 in PSC tissues. CONCLUSION: The present study reveals the vital role of USP9X in regulating EMT, angiogenesis and immune infiltration and inhibiting metastasis of PSC via downregulating MMP9, which provides a new effective therapeutic target for PSC.

Adjuvant Atezolizumab in Patients with Sarcomatoid Renal Cell Carcinoma: A Prespecified Subgroup Analysis of IMmotion010.

Patients with sarcomatoid renal cell carcinoma (sRCC) have a poor prognosis. In the randomised, double-blind phase 3 IMmotion010 trial (NCT03024996), adjuvant atezolizumab did not demonstrate a disease-free survival (DFS) benefit versus placebo in the overall population of patients with locoregional renal cell carcinoma with an increased risk of recurrence following surgery. This prespecified subgroup analysis of efficacy and safety was completed in 104 patients with sRCC. Baseline characteristics were similar between treatment arms. At a median follow-up of 45 mo, the median DFS was not evaluable (NE; 95% confidence interval [CI], 12 mo-NE) in the atezolizumab arm (n = 37) and 23 mo (95% CI, 11-NE) in the placebo arm (n = 66; hazard ratio 0.77 [95% CI, 0.44-1.4]). In the sRCC subgroup, grade 3/4 treatment-related adverse events (TRAEs) occurred in one patient (2.7%) in the atezolizumab arm and two patients (3.0%) in the placebo arm. By comparison, 54 of 353 patients (15%) and 16 of 317 patients (5.0%) with non-sarcomatoid histology reported grade 3/4 TRAEs in the respective arms. In conclusion, the difference in DFS was not statistically significant between adjuvant atezolizumab and placebo in patients with sRCC. The safety profile was similar between patients with sRCC and non-sRCC. PATIENT SUMMARY: Patients with a specific type of locoregional kidney cancer (tumours with sarcomatoid features) were treated with atezolizumab or placebo after surgery. Slightly more patients treated with atezolizumab lived longer without the disease getting worse than those treated with placebo, although this finding was not statistically significant. The side effects were similar to those seen in patients with other types of kidney cancer treated with atezolizumab in the same study (IMmotion010). In patients with sarcomatoid kidney cancer, atezolizumab was tolerable and may be more effective than placebo, but this requires further study.

Metastatic Urothelial Carcinoma With Sarcomatoid Subtype After Robot-Assisted Radical Cystectomy Successfully Treated With Pembrolizumab.

A 76-year-old man who was diagnosed with urothelial carcinoma (UC) in the bladder diverticulum was referred to our institution. The patient was diagnosed with muscle-invasive bladder cancer, which was confirmed by magnetic resonance imaging that showed tumor invasion into the fatty tissue surrounding the diverticulum. After two cycles of neoadjuvant gemcitabine and cisplatin, he underwent robot-assisted radical cystectomy (RARC) with pelvic lymph node dissection followed by intracorporeal ileal conduit. The histopathologic diagnosis of the bladder tumor was UC with squamous differentiation and sarcomatoid subtype and ypT3bN0M0 without positive surgical margins. The patient refused any adjuvant therapy. Six months after RARC, the patient visited our institution with a complaint of suddenly occurring generalized pain. Because 18F-fluorodeoxyglucose positron emission tomography-CT showed multiple metastases, including bone, para-aortic lymph nodes, and pleura, pembrolizumab was initiated as a second-line treatment. After two courses of pembrolizumab, the patient's symptoms remarkably improved, and the abnormal systemic accumulation on PET-CT almost disappeared. After 26 months of continuous treatment with pembrolizumab, the patient remains disease-free. Several studies have been reported that focused on tumor subtypes and programmed cell death ligand 1 (PD-L1)-positive tumor cells as candidate biomarkers in relation to the efficacy of pembrolizumab. The higher proportion of PD-L1-positive cells in the sarcomatoid subtype may have resulted in favorable oncological outcomes compared with pure UC.

Predicting MET exon 14 skipping mutation in pulmonary sarcomatoid carcinoma by whole-tumour texture analysis combined with clinical and conventional contrast-enhanced computed tomography features.

Background: Pulmonary sarcomatoid carcinoma (PSC) is a rare, highly malignant type of non-small cell lung cancer (NSCLC) with a poor prognosis. Targeted drugs for MET exon 14 (METex14) skipping mutation can have considerable clinical benefits. This study aimed to predict METex14 skipping mutation in PSC patients by whole-tumour texture analysis combined with clinical and conventional contrast-enhanced computed tomography (CECT) features. Methods: This retrospective study included 56 patients with PSC diagnosed by pathology. All patients underwent CECT before surgery or other treatment, and both targeted DNA- and RNA-based next-generation sequencing (NGS) were used to detect METex14 skipping mutation status. The patients were divided into two groups: METex14 skipping mutation and nonmutation groups. Overall, 1,316 texture features of the whole tumour were extracted. We also collected 12 clinical and 20 conventional CECT features. After dimensionality reduction and selection, predictive models were established by multivariate logistic regression analysis. Models were evaluated using the area under the curve (AUC), and the clinical utility of the model was assessed by decision curve analysis. Results: METex14 skipping mutation was detected in 17.9% of PSCs. Mutations were found more frequently in those (I) who had smaller long- or short-axis diameters (P=0.02, P=0.01); (II) who had lower T stages (I, II) (P=0.02); and (III) with pseudocapsular or annular enhancement (P=0.03). The combined model based on the conventional and texture models yielded the best performance in predicting METex14 skipping mutation with the highest AUC (0.89). The conventional and texture models also had good performance (AUC =0.83 conventional; =0.88 texture). Conclusions: Whole-tumour texture analysis combined with clinical and conventional CECT features may serve as a noninvasive tool to predict the METex14 skipping mutation status in PSC.

Investigating esophageal sarcomatoid carcinoma and its comparison with esophageal squamous cell carcinoma on clinicopathological characteristics, prognosis, and radiomics features: a retrospective study.

Introduction: Esophageal sarcomatoid carcinoma (ESC) is a rare pathological subtype of esophageal carcinomas, wherein its epithelial component typically demonstrates squamous cell carcinoma (SCC). However, the clinicopathological features and prognosis of ESC remain unclear, alongside its unique aspects compared to esophageal SCC (ESCC). Methods: Between January 2008 and December 2018, we retrospectively reviewed 67 ESC patients treated at West China Hospital. Among them, 51 patients with resected ESC were matched with 98 resected ESCC patients over the same period using propensity score matching at 1:2. The survival time and radiomics features of the two groups were compared. Results: A total of 59 patients with resected ESC and eight patients with non-resected ESC were enrolled. Progression-free survival (PFS) and overall survival (OS) were significantly different in patients with different TNM stages (p < 0.001). A multivariate analysis showed that length of tumor was an independent factor for OS in resetable ESC (p = 0.041). Among matched ESC and ESCC patients, OS was significantly longer for patients with ESC than those with ESCC (5-year OS, 61.1% vs. 43.6%; HR 0.59, 95% CI 0.35-0.96; p = 0.032). A Rad-score for discriminating ESC from ESCC containing two CT-derived radiomics features was developed [area under the curve: 0.823 (95% CI 0.732-0.913) in the training cohort and 0.828 (95% CI 0.636-1.000) in the validation cohort, respectively]. Conclusions: ESC has a better prognosis when compared with ESCC. By developing a radiomics prediction model, we provide reliability and convenience for the differential diagnosis of ESC from ESCC.

Epithelial-mesenchymal transition associated markers in sarcomatoid transformation of clear cell renal cell carcinoma.

Epithelial-mesenchymal transition (EMT) plays a pivotal role in the development and progression of many cancers. Partial EMT (pEMT) could represent a critical step in tumor migration and dissemination. Sarcomatoid renal cell carcinoma (sRCC) is an aggressive form of renal cell carcinoma (RCC) composed of a carcinomatous (sRCC-Ca) and sarcomatous (sRCC-Sa) component. The role of (p)EMT in the progression of RCC to sRCC remains unclear. The aim of this study was to investigate the involvement of (p)EMT in RCC and sRCC. Tissue samples from 10 patients with clear cell RCC (ccRCC) and 10 patients with sRCC were selected. The expression of main EMT markers (miR-200 family, miR-205, SNAI1/2, TWIST1/2, ZEB1/2, CDH1/2, VIM) was analyzed by qPCR in ccRCC, sRCC-Ca, and sRCC-Sa and compared to non-neoplastic tissue and between both groups. Expression of E-cadherin, N-cadherin, vimentin and ZEB2 was analyzed using immunohistochemistry. miR-200c was downregulated in sRCC-Ca compared to ccRCC, while miR-200a was downregulated in sRCC-Sa compared to ccRCC. CDH1 was downregulated in sRCC-Sa when compared to any other group. ZEB2 was downregulated in ccRCC and sRCC compared to corresponding non-neoplastic kidney. A positive correlation was observed between CDH1 expression and miR-200a/b/c. Our results suggest that full EMT is not present in sRCC. Instead, discreet molecular differences exist between ccRCC, sRCC-Ca, and sRCC-Sa, possibly representing distinct intermediary states undergoing pEMT.

Germ Cell Tumor of the Testis: Lethal Subtypes of a Curable Cancer.

Germ cell tumor of the testis (GCT) is a curable cancer even when it is widely metastatic; however, outcomes can differ based on tumor histology. Chemo-resistance in certain phenotypes, such as teratoma and yolk sac tumor, contributes to poor clinical outcomes in some patients with GCT. Despite this resistance to S-YSTemic therapy, many of these tumor subtypes remain amenable to surgical resection and possible cure. In this study, we report on a series of seven patients highlighting two chemo-resistant subtypes of nonseminomatous germ cell tumor (NSGCT), sarcomatoid yolk sac tumor (S-YST), and epithelioid trophoblastic tumor (ETT) for which early resection rather than additional salvage chemotherapy or high-dose intense chemotherapy might provide a superior clinical outcome and enhance cure rate.

Epigenomic signatures of sarcomatoid differentiation to guide the treatment of renal cell carcinoma.

Renal cell carcinoma with sarcomatoid differentiation (sRCC) is associated with poor survival and a heightened response to immune checkpoint inhibitors (ICIs). Two major barriers to improving outcomes for sRCC are the limited understanding of its gene regulatory programs and the low diagnostic yield of tumor biopsies due to spatial heterogeneity. Herein, we characterized the epigenomic landscape of sRCC by profiling 107 epigenomic libraries from tissue and plasma samples from 50 patients with RCC and healthy volunteers. By profiling histone modifications and DNA methylation, we identified highly recurrent epigenomic reprogramming enriched in sRCC. Furthermore, CRISPRa experiments implicated the transcription factor FOSL1 in activating sRCC-associated gene regulatory programs, and FOSL1 expression was associated with the response to ICIs in RCC in two randomized clinical trials. Finally, we established a blood-based diagnostic approach using detectable sRCC epigenomic signatures in patient plasma, providing a framework for discovering epigenomic correlates of tumor histology via liquid biopsy.

Case report: Sarcomatoid renal cell carcinoma masquerading as hydronephrosis.

Sarcomatoid renal cell carcinoma (SRCC), a manifestation of sarcomatoid dedifferentiation in renal cell carcinoma, is characterized by elevated invasiveness and a grim prognosis. Typically, SRCC patients present with advanced or metastatic conditions and survival rates rarely extend beyond one year. In this study, we describe a case of SRCC characterized by the patient exhibiting right flank pain without hematuria. Initially, imaging interpretations led to a diagnosis of severe hydronephrosis. Subsequently, an open right nephrectomy post-surgery confirmed the pathology of sarcomatoid renal cell carcinoma.

Urinary Bladder Carcinosarcoma (Sarcomatoid Carcinoma) With Long Survival After Transurethral Resection: A Case Report.

Carcinosarcoma or sarcomatoid carcinoma of the urinary bladder is a rare but aggressive bladder cancer characterized by malignant epithelial and mesenchymal components, with only a few cases reported in the literature so far. In this report, we discuss a case of a 74-year-old female nonsmoker who presented with intermittent hematuria and passage of clots in the last four months. Radiographic images showed an irregular mass lesion (6.2 x 6 cm) in the left lateral wall of the urinary bladder near to left vesicoureteral junction. The mass was completely removed with transurethral resection of the bladder tumor (TUR-BT). Histopathological study revealed high-grade carcinosarcoma, and immunohistochemistry showed diffuse positivity for vimentin, pan-cytokeratin (CK) and CK7, epithelial membrane antigen (EMA), and CK5/6. The patient declined radical cystectomy and only agreed to receive intravesical chemotherapy (gemcitabine), and she remains alive after more than four years of follow-up. Carcinosarcoma of the urinary bladder is a rare tumor primarily affecting older people, and it is most commonly treated with radical cystectomy and different combination treatments such as chemotherapy and radiation. However, tumor resection followed by intravesical chemotherapy may be an alternative option in the early stages of bladder carcinosarcoma for some patients, thereby avoiding the need for aggressive treatments, especially for elderly patients who decline to undergo radical surgery.

Role of immunotherapy in pulmonary sarcomatoid carcinoma: review of current approaches and related biomarkers.

Pulmonary sarcomatoid carcinoma (PSC), a rare subtype of non-small cell lung cancer, is highly malignant and has a poor prognosis. Treatments for PSC are presently limited. Traditional treatments provide fewer benefits to PSC patients and are associated with early recurrence and metastasis. Surgical intervention is the preferred option for early-stage PSC patients, whereas chemotherapy, radiotherapy, immunotherapy, and other targeted therapies are recommended for advanced PSC patients. Targeted therapy is only effective in a small number of PSC patients. The initial efficacy of immune checkpoint inhibitors has been acceptable in patients with advanced PSC; therefore, much attention on related biomarkers has been sought. This article aimed to review the research progress of PSC immunotherapy and related diagnostic and prognostic biomarkers in recent years.

Advances in immunotherapy for pulmonary sarcomatoid carcinoma Pulmonary sarcomatoid carcinoma (PSC), a rare subtype of non-small cell lung cancer (NSCLC), is highly malignant and has a poor prognosis. Traditional treatments provide fewer benefits to PSC patients and are associated with early recurrence and metastasis. Targeted therapy is only effective in a small number of PSC patients. The initial efficacy of immune checkpoint inhibitors (ICIs) has been acceptable in patients with advanced PSC, therefore, much attention on related biomarkers has been sought. This article aimed to review the research progress of PSC immunotherapy and related diagnostic and prognostic biomarkers in recent years.

Sarcomatoid Dedifferentiation as a Predictor of Cancer-Specific Mortality in Surgically Treated Localized Renal Cell Carcinoma.

BACKGROUND: In contemporary surgically treated patients with localized high-grade (G3 or G4) clear-cell renal cell carcinoma (ccRCC), it is not known whether presence of sarcomatoid dedifferentiation is an independent predictor and/or an effect modifier, when cancer-specific mortality (CSM) represents an endpoint. METHODS: Within the Surveillance, Epidemiology, and End Results database, all surgically treated localized high-grade ccRCC patients treated between 2010 and 2020 were identified. Univariable and multivariable Cox-regression models were used. RESULTS: In 18,853 surgically treated localized high-grade (G3 or G4) ccRCC patients, 5-year CSM-free survival was 87% (62% vs. 88% with vs. without sarcomatoid dedifferentiation, p < 0.001). Presence of sarcomatoid dedifferentiation was an independent predictor of higher CSM (hazard ratio [HR] 1.8, p < 0.001). In univariable survival analyses predicting CSM, presence versus absence of sarcomatoid dedifferentiation in G3 versus G4 yielded the following hazard ratios: HR 1.0 in absent sarcomatoid dedifferentiation in G3; HR 2.7 (p < 0.001) in absent sarcomatoid dedifferentiation in G4; HR 3.9 (p < 0.001) in present sarcomatoid dedifferentiation in G3; HR 5.1 (p < 0.001) in present sarcomatoid dedifferentiation in G4. Finally, in multivariable Cox-regression analyses, the interaction terms defining present versus absent sarcomatoid dedifferentiation in G3 versus G4 represented independent predictors of higher CSM. CONCLUSIONS: In contemporary surgically treated patients with localized high-grade ccRCC, sarcomatoid dedifferentiation is not only an independent multivariable predictor of higher CSM, but also interacts with tumor grade and results in even better ability to predict CSM.

Colorectal Sarcomatoid Carcinoma: 30-Year Experience.

Background: Primary colorectal sarcomatoid carcinoma is a rare and aggressive malignant neoplasm that displays mixed epithelial and mesenchymal differentiation, with uncertain histogenesis. First described in 1986, there is a paucity of literature related to this condition and there are no evidence-based treatment guidelines. The aim of our study is to present our 30-year experience with primary colorectal sarcomatoid carcinoma. Methods: Retrospective single-center analysis of all patients treated for primary colorectal sarcomatoid carcinoma from 1992 to 2022. The primary outcome was response to treatment strategy and overall survival. Results: A total of six cases met eligibility criteria. Three were male (50%) with a mean age at diagnosis of 59 years (range, 49-72). Four neoplasms were located in the rectum (66%) and two in the colon. Mean tumor size at diagnosis was 4.8 cm (range, 2.8-7.0). Three patients were treated endoscopically and three underwent oncologic surgical resection. Five experienced recurrence and one expired from other comorbidities. The mean survival among those with colonic and rectal sarcomatoid carcinoma was 7 months (range, 3-11) and 39 months (range, 9-60), respectively. Discussion: Primary colorectal sarcomatoid carcinoma is a rare malignant tumor with poor prognosis. Treatment modalities have not been standardized and despite multimodal therapy, disease recurrence and/or metastasis is likely to occur. Further studies are necessary to determine optimal treatment to improve outcomes.

Tracing Tumor Heterogeneity of Pleomorphic Carcinoma of the Lung.

INTRODUCTION: Pulmonary pleomorphic carcinoma (PPC) is an aggressive and highly heterogeneous NSCLC whose underlying biology is still poorly understood. METHODS: A total of 42 tumor areas from 20 patients with PPC were microdissected, including 39 primary tumors and three metastases, and the histologically distinct components were subjected to whole exome sequencing separately. We further performed in silico analysis of microdissected bulk RNA sequencing and methylation data of 28 samples from 14 patients with PPC. We validated our findings using immunohistochemistry. RESULTS: The epithelial and the sarcomatoid components of PPCs shared a large number of genomic alterations. Most mutations in cancer driver genes were clonal and truncal between the two components of PPCs suggesting a common ancestor. The high number of alterations in the RTK-RAS pathway suggests that it plays an important role in the evolution of PPC. The metastases morphologically and genetically resembled the epithelial or the sarcomatoid components of the tumor. The transcriptomic and epigenetic profiles of the sarcomatoid components of PPCs with matched squamous-like or adenocarcinoma-like components differed from each other, and they shared more similarities to their matched epithelial components. NCAM1/CD56 was preferentially expressed in the sarcomatoid component of squamous-like PPCs, whereas CDH1/E-Cadherin expression was down-regulated in the sarcomatoid component of most PPCs. CONCLUSION: Lung adenocarcinoma-like PPCs are mainly driven by RTK-RAS signaling, whereas epithelial-mesenchymal transition programs as highlighted by increased NCAM1 and decreased CDH1 expression govern the epithelial-sarcomatoid transition between the clonally related tumor components. Several alterations in PPCs pinpoint therapeutic opportunities.

Sarcomatoid malignant pleural mesothelioma: a case of long-term recurrence-free survival following curative intent surgery alone.

BACKGROUND: Curative intent surgery may be indicated for some patients with resectable early stage malignant pleural mesothelioma (MPM). However, sarcomatoid MPM is a highly aggressive subtype for which curative intent surgery is generally not recommended. CASE PRESENTATION: We present the case of a 63-year-old man who presented with dyspnea and chest tightness. Computed tomography revealed pleural thickening and nodular lesions. A pleural biopsy confirmed lymphohistiocytoid MPM (cT1N0M0, stage IA), prompting surgical intervention. The patient underwent left extrapleural pneumonectomy (EPP), and the final diagnosis was sarcomatoid MPM (pT2N0M0, stage IB). Although post-operative chemotherapy was planned, the patient refused additional treatment, because of the introduction of home oxygen therapy, and has remained recurrence-free for 10 years after the surgery. CONCLUSIONS: This case presents a noteworthy instance of achieving long-term recurrence-free survival solely through curative intent surgery for sarcomatoid MPM. It highlights the potential efficacy of surgical intervention in managing this aggressive subtype, offering a glimmer of hope for improved outcomes. Further research is warranted to better define the role of surgery in the treatment of sarcomatoid MPM.

FK228 suppress the growth of human malignant pleural mesothelioma tumor independent to epithelioid or non-epithelioid histology.

Human malignant pleural mesothelioma (hMPM) is an aggressive, rare disease with a poor prognosis. Histologically, MPM is categorized into epithelioid, biphasic, and sarcomatoid subtypes, with the epithelioid subtype generally displaying a better response to treatment. Conversely, effective therapies for the non-epithelioid subtypes are limited. This study aimed to investigate the potential role of FK228, a histone deacetylase inhibitor, in the suppression of hMPM tumor growth. We conducted a comprehensive analysis of the histological and molecular characteristics of two MPM cell lines, CRL-5820 (epithelioid) and CRL-5946 (non-epithelioid). CRL-5946 cells and non-epithelioid patient-derived xenografted mice exhibited heightened growth rates compared to those with epithelioid MPM. Both CRL-5946 cells and non-epithelioid mice displayed a poor response to cisplatin. However, FK228 markedly inhibited the growth of both epithelioid and non-epithelioid tumor cells in vitro and in vivo. Cell cycle analysis revealed FK228-induced G1/S and mitotic arrest in MPM cells. Caspase inhibitor experiments demonstrated that FK228-triggered apoptosis occurred via a caspase-dependent pathway in CRL-5946 but not in CRL-5820 cells. Additionally, a cytokine array analysis showed that FK228 reduced the release of growth factors, including platelet-derived and vascular endothelial growth factors, specifically in CRL-5946 cells. These results indicate that FK228 exhibits therapeutic potential in MPM by inducing cytotoxicity and modulating the tumor microenvironment, potentially benefiting both epithelioid and non-epithelioid subtypes.