Malignant T cells in cutaneous T-cell lymphoma lesions contain decreased levels of the antiapoptotic protein Ku70

The Tumor Microenvironment as a Therapeutic Target in Cutaneous T Cell Lymphoma

Cutaneous T cell lymphomas (CTCLs) are a heterogeneous group of non-Hodgkin lymphomas, with mycosis fungoides and Sézary syndrome being the two common subtypes. Despite the substantial improvement in early-stage diagnosis and treatments, some patients still progress to the advanced stage with an elusive underpinning mechanism. While this unsubstantiated disease mechanism coupled with diverse clinical outcomes poses challenges in disease management, emerging evidence has implicated the tumor microenvironment in the disease process, thus revealing a promising therapeutic potential of targeting the tumor microenvironment. Notably, malignant T cells can shape their microenvironment to dampen antitumor immunity, leading to Th2-dominated responses that promote tumor progression. This is largely orchestrated by alterations in cytokines expression patterns, genetic dysregulations, inhibitory effects of immune checkpoint molecules, and immunosuppressive cells. Herein, the recent insights into the determining factors in the CTCL tumor microenvironment that support their progression have been highlighted. Also, recent advances in strategies to target the CTCL tumor micromovement with the rationale of improving treatment efficacy have been discussed.

Endothelial VEGFR2-PLCγ signaling regulates vascular permeability and antitumor immunity through eNOS/Src

Endothelial phospholipase Cγ (PLCγ) is essential for vascular development; however, its role in healthy, mature, or pathological vessels is unexplored. Here, we show that PLCγ was prominently expressed in vessels of several human cancer forms, notably in renal cell carcinoma (RCC). High PLCγ expression in clear cell RCC correlated with angiogenic activity and poor prognosis, while low expression correlated with immune cell activation. PLCγ was induced downstream of vascular endothelial growth factor receptor 2 (VEGFR2) phosphosite Y1173 (pY1173). Heterozygous Vegfr2Y1173F/+ mice or mice lacking endothelial PLCγ (Plcg1iECKO) exhibited a stabilized endothelial barrier and diminished vascular leakage. Barrier stabilization was accompanied by decreased expression of immunosuppressive cytokines, reduced infiltration of B cells, helper T cells and regulatory T cells, and improved response to chemo- and immunotherapy. Mechanistically, pY1173/PLCγ signaling induced Ca2+/protein kinase C-dependent activation of endothelial nitric oxide synthase (eNOS), required for tyrosine nitration and activation of Src. Src-induced phosphorylation of VE-cadherin at Y685 was accompanied by disintegration of endothelial junctions. This pY1173/PLCγ/eNOS/Src pathway was detected in both healthy and tumor vessels in Vegfr2Y1173F/+ mice, which displayed decreased activation of PLCγ and eNOS and suppressed vascular leakage. Thus, we believe that we have identified a clinically relevant endothelial PLCγ pathway downstream of VEGFR2 pY1173, which destabilizes the endothelial barrier and results in loss of antitumor immunity.

Increased Chlormethine-Induced DNA Double-Stranded Breaks in Malignant T Cells from Mycosis Fungoides Skin Lesions

Mycosis fungoides (MF) is a type of cutaneous T-cell lymphoma. Chlormethine (CL) is recommended as first-line therapy for MF, with a major purpose to kill tumor cells through DNA alkylation. To study the extent of treatment susceptibility and tumor specificity, we investigated the gene expression of different DNA repair pathways, DNA double-stranded breaks, and tumor cell proliferation of clonal TCR Vβ+ tumor cell populations in cutaneous T-cell lymphoma skin cells on direct exposure to CL. Healthy human T cells were less susceptible to CL exposure than two T-lymphoma cell lines, resulting in higher proportions of viable cells. Interestingly, in T cells from MF lesions, we observed a downregulation of several important DNA repair pathways, even complete silencing of RAD51AP1, FANC1, and BRCA2 involved in homologous recombination repair. In the presence of CL, the double-stranded DNA breaks in malignant MF skin T cells increased significantly as well as the expression of the apoptotic gene CASP3. These data point toward an important effect of targeting CL on MF skin tumor T cells, which support CL use as an early cutaneous lymphoma treatment and can be of synergistic use, especially beneficial in the setting of combination skin-directed therapies for cutaneous T-cell lymphoma.

Subcutaneous B Cell Lymphoma in a Dog from the West Indies

A 9-year-old male castrated mixed-breed dog from the West Indies was presented for multiple, nonpainful, nodular, circumscribed, subcutaneous masses located on the dorsum, lateral thorax, head, forelimbs, and scrotum. En bloc surgical resection of a mass on the right paw, left forehead, and left medial forelimb with proportional margins was performed. Three punch biopsies were taken from the masses located along the right lateral flank. Histopathologic and immunohistochemistry (IHC) examination of the skin lesions revealed a diagnosis of subcutaneous B cell lymphoma. Thoracic radiographs and abdominal ultrasound were negative for signs of gross metastatic disease. Chemotherapeutic intervention included intravenous doxorubicin (30 mg/m²) administered at 3-week intervals for 3 treatments and oral prednisone (2 mg/kg/d) for 3 weeks. There were no complications following the chemotherapy protocol. As of 3 years, there has been no regrowth of the tumors and the patient continues to be cancer free. To date, this is the first reported case of subcutaneous B cell lymphoma diagnosed in a dog treated successfully with gross tumor resection and chemotherapy.

The Incidence of Other Primary Cancers in Patients with Cutaneous Lymphoma

Background

Skin cancer is the most common other primary cancer in patients with lymphoma. However, an intriguing association between cutaneous lymphoma and other primary cancers has been suggested in a few studies.

Objective

This study investigated other primary cancers in patients with cutaneous lymphoma to evaluate the risk for occurrence of each type of cancer.

Methods

We screened for other primary cancers in 428 patients with cutaneous lymphoma. Clinical features were analyzed according to the lineage and origin of the lymphomas. We calculated the standardized incidence ratio with statistical analysis for each group according to age.

Results

Among 330 patients with cutaneous T cell lymphoma and 98 with cutaneous B cell lymphoma, a total of 43 cancers in 38 patients were finally included. Other primary cancers were prevalent in patients with cutaneous B cell lymphoma and patients with secondary cutaneous lymphoma. However, those differences were not significant when the age was calibrated by multiple logistic regression. Metachronously higher standardized incidence ratios were observed for primary lung (standardized incidence ratio [SIR], 14.81; 95% confidence interval [CI], 3.05~39.54), skin (SIR, 68.05; 95% CI, 14.03~181.62), and breast (SIR, 12.91; 95% CI, 1.56~41.41) cancers with statistical significance.

Conclusion

Other primary cancers more preferentially occurred in patients with cutaneous lymphoma. Clinicians should carefully examine patients with cutaneous lymphoma for other cancers, especially lung, skin, and breast cancers.