Myelodysplastic Neoplasms (MDS): The Current and Future Treatment Landscape

Myelodysplastic neoplasms (MDS) are a heterogenous clonal disorder of hemopoietic stem cells characterized by cytomorphologic dysplasia, ineffective hematopoiesis, peripheral cytopenias and risk of progression to acute myeloid leukemia (AML). Our understanding of this disease has continued to evolve over the last century. More recently, prognostication and treatment have been determined by cytogenetic and molecular data. Specific genetic abnormalities, such as deletion of the long arm of chromosome 5 (del(5q)), TP53 inactivation and SF3B1 mutation, are increasingly associated with disease phenotype and outcome, as reflected in the recently updated fifth edition of the World Health Organization Classification of Hematolymphoid Tumors (WHO5) and the International Consensus Classification 2022 (ICC 2022) classification systems. Treatment of lower-risk MDS is primarily symptom directed to ameliorate cytopenias. Higher-risk disease warrants disease-directed therapy at diagnosis; however, the only possible cure is an allogenic bone marrow transplant. Novel treatments aimed at rational molecular and cellular pathway targets have yielded a number of candidate drugs over recent years; however few new approvals have been granted. With ongoing research, we hope to increasingly offer our MDS patients tailored therapeutic approaches, ultimately decreasing morbidity and mortality.

Comorbid Ankylosing Spondylitis and Systemic Lupus Erythematosus: A Therapeutic Challenge

Ankylosing spondylitis (AS) and systemic lupus erythematosus (SLE) are common rheumatologic ailments that cause multiorgan system disease. The incidence of lupus and AS in the same patient is rare and has seldom been described in the literature. Comorbid lupus and AS provide interesting diagnostic and therapeutic challenges. Here, we present a case of comorbid lupus and AS, discuss the diagnostic challenges in diagnosing these conditions, and put forth possible therapeutic interventions that may benefit similar patients.

The prevalence and clinical significance of HER2 expression in prostate adenocarcinoma

AIMS

Abnormalities in HER2 are well-established oncogenic drivers and are approved therapeutic targets in various malignancies. Prior studies evaluating HER2 expression in prostate cancer (PCa) have yielded variable results. Most of these studies used immunohistochemistry scoring systems based on breast cancer data. The goal of this study was to determine the prevalence and clinical significance of HER2 expression using a scoring system that better reflects the HER2 staining pattern observed in PCa.

METHODS

We randomly selected similar numbers of localized low risk (AJCC stage I), locally advanced (AJCC stages II & III), and metastatic (AJCC stage IV) PCa patients treated at the DC VA Medical Center between 2000 and 2022. Among them, we included patients who had sufficient PCa tissue samples and clinical information required for this analysis. Two experienced pathologists independently scored HER2 expression (Ventana Pathway anti-HER2) according to a modified gastric cancer HER2 scoring system.

RESULTS

Out of the 231 patients included, 85 % self-identified as Black. 58.9 % of patients expressed HER2 (1+: 35.5 %; 2+: 18.2 %; 3+: 5.2 %). Validity of the results was confirmed using the HercepTest antibody. Higher HER2 expression was associated with a higher Gleason Score/Grade Group and advanced disease.

CONCLUSIONS

Our findings support the adverse prognostic impact on HER2 in PCa. We propose the use of a modified scoring system to evaluate HER2 expression in PCa. The observed high prevalence of HER2 expression supports the consideration of novel HER2-targeted therapies addressing even low levels of HER2 expression in future PCa trials.

Novel Therapeutics for Malaria

Malaria is a potentially fatal disease caused by protozoan parasites of the genus Plasmodium. It is responsible for significant morbidity and mortality in endemic countries of the tropical and subtropical world, particularly in Africa, Southeast Asia, and South America. It is estimated that 247 million malaria cases and 619,000 deaths occurred in 2021 alone. The World Health Organization's (WHO) global initiative aims to reduce the burden of disease but has been massively challenged by the emergence of parasitic strains resistant to traditional and emerging antimalarial therapy. Therefore, development of new antimalarial drugs with novel mechanisms of action that overcome resistance in a safe and efficacious manner is urgently needed. Based on the evolving understanding of the physiology of Plasmodium, identification of potential targets for drug intervention has been made in recent years, resulting in more than 10 unique potential anti-malaria drugs added to the pipeline for clinical development. This review article will focus on current therapies as well as novel targets and therapeutics against malaria.

Androgen receptor amplification in mesonephric remnants

Mesonephric remnants (MRs) are embryonic vestiges most commonly found in female pathology specimens from the lateral wall of the cervix. The highly regulated genetic programme of mesonephric duct development has been well characterised in animals based on traditional surgical castration and knockout mouse experiments. However, the process is incompletely understood in humans. MRs are believed to give rise to mesonephric neoplasms, which are rare tumours with uncertain pathophysiology. There is a dearth of molecular studies on mesonephric neoplasms in part due to their rarity. Here, we report the results of next-generation sequencing of MR, which identified amplification of the androgen receptor gene for the first time to the best of our knowledge and discuss the potential implications in the context of the literature.

Rosai-Dorfman Disease of the Rectum: Newly Identified Genetic Point Mutations and Robotic Resection

Rosai-Dorfman disease (RDD) is a rare disease characterized by histiocytic proliferation which typically presents as massive, painless, cervical lymphadenopathy in children or young adults. GI involvement is exceedingly rare with only 20 documented cases to date. Of those 20 cases, only 3 cases have involved the rectum. Here, we present 2 cases of rectal RDD with attention paid to the diagnostic and technical challenges presented by this disease. When presenting as a perirectal mass, RDD can be mistaken for other lesions to include malignancy, leading to surgical removal. We present a video of a robotic low-anterior resection with intracorporeal anastomosis in order to remove a pelvic mass involving the rectum, initially considered to be a stromal tumor. In addition, we describe a copy number variation in AKT and 3 point mutations detected by next generation sequencing, which had not been previously reported in association with this disease.

Central Centrifugal Cicatricial Alopecia Associated With PDL1 Loss and Increased Expression of Caspase 3: A Case Series

ABSTRACT

Central centrifugal cicatricial alopecia (CCCA) is a scarring alopecia that disproportionately affects patients with skin of color. Genetic studies have revealed that approximately 30% of CCCAs are associated with peptidyl arginine deiminase 3 misfolding mutations. Patients with CCCA usually have a poor prognosis with progressive and permanent hair loss. To further characterize CCCA, we evaluated the inflammatory milieu, PDL1, and caspase 3 expression. The data support the idea of CCCA being a CD4-predominant T-cell process. The loss of PDL1 and increase in caspase 3 expression raises the possibility of involvement of the PD1/PDL1 pathway in CCCA.

KRAS G12D mutation in Brunner gland adenoma

Brunner gland lesions (BGLs) encompass benign proliferations of the homonymous glands and have been designated as hyperplasia, adenoma (BGA), hamartoma or nodule. In general terms, lesions larger than 0.5 cm are considered true neoplasia with unknown malignant potential and unclear pathogenesis. Genetic alterations have seldom been reported in BGL, and include SMAD4/DPC4 and LRIG1, but not KRAS (Kirsten rat sarcoma viral oncogene homologue) to the best of our knowledge.We present the case of a man in his 60s, evaluated for iron deficiency anaemia harbouring a 1.5 cm BGA found by duodenoscopy. Immunohistochemistry failed to reveal microsatellite instability, and next-generation sequencing revealed a KRAS G12D point mutation.

Secondary Stabbing Headache Associated with COVID-19: a Case Report

Although COVID-19 is mainly an acute viral illness, persistent symptoms are common. However, headache is not a frequent sequela of this disease. Furthermore, stabbing/ice-pick cephalalgia has been reported in < 10% of cases of COVID-19, and recurrent forms occurring after vaccination against the disease have not been published yet. We present here an unusual short-lasting unilateral stabbing/ice-pick headache with recurrent periodicity over 10 months, which may represent a sequela of COVID-19. The cephalalgia presented in a 55-year-old male with no significant medical problems approximately 4 months after the acute onset of COVID-19, and recurred twice 12 days after the second dose of COVID-19 vaccination with BNT162b2 (Pfizer). This report represents a contribution to the semiological pattern of COVID-19-related cephalea.

Neurothekeoma With PI3K w552*, ALK P1469S, SMO G461S, and ERBB3 L77M Genetic Alterations

ABSTRACT

Neurothekeoma, a lesion of possible fibrohistiocytic origin, is a rare, benign, superficial soft tissue tumor, histologically subclassified in 3 types: myxoid, cellular, or mixed. It clinically presents as a solitary, pink to brown nodule, ranging from 0.3 to 2.0 cm. Four point mutations (PI3K w552*, ALK P1469S, SMO G461S, and ERBB3 L77M) were identified by next-generation sequencing of a neurothekeoma presenting in the left inner thigh of a 53-year-old man. We highlight novel genetic alterations (SMO G461S and ERBB3 L77M) and previously known mutations (PI3KCA w552* and ALK P1469S) that play a role in other pathogenic pathways, but to the best of our knowledge, these have not yet been reported in neurothekeoma.

Concurrent Waldenstrom’s Macroglobulinemia and Myelodysplastic Syndrome with a Sequent t(10;13)(p13;q22) Translocation

Myelodysplastic syndromes (MDS) and Waldenstrom’s macroglobulinemia (WM) are rarely synchronous. Ineffective myelopoiesis/hematopoiesis with clonal unilineage or multilineage dysplasia and cytopenias characterize MDS. Despite a myeloid origin, MDS can sometimes lead to decreased production, abnormal apoptosis or dysmaturation of B cells, and the development of lymphoma. WM includes bone marrow involvement by lymphoplasmacytic lymphoma (LPL) secreting monoclonal immunoglobulin M (IgM) with somatic mutation (L265P) of myeloid differentiation primary response 88 gene (MYD88) in 80–90%, or various mutations of C-terminal domain of the C-X-C chemokine receptor type 4 (CXCR4) gene in 20–40% of cases. A unique, progressive case of concurrent MDS and WM with several somatic mutations (some unreported before) and a novel balanced reciprocal translocation between chromosomes 10 and 13 is presented below.

Hepatoid prostatic carcinoma with adrenal metastasis and novel genetic alterations

Hepatoid carcinoma (HC) encompasses epithelial extrahepatic tumors exhibiting features of hepatocellular carcinoma (HCC) both by morphology and immunohistochemistry. Distinguishing metastatic HCC from HC may be challenging, particularly when limited material, such as a cytologic specimen, is available. HC from prostatic origin is unusual and has only rarely been characterized by cytology. Herein we present an 86-year-old male with history of castration-resistant prostate cancer developing a left adrenal gland nodule. Fine needle aspiration revealed a poorly differentiated malignant neoplasm diagnosed as metastatic hepatoid prostatic adenocarcinoma based on immunohistochemistry (positive for HepPar1, AFP, NKX3.1, PSMA, and Racemase; and negative for CK7, CK20, cytokeratin 34betaE12, p63, and Arg-1). Because prostatic carcinoma with hepatoid features is rare, and the patient had failed standard therapy, next generation sequencing was performed in an attempt to identify druggable molecular targets. Well-known prostate carcinoma-related alterations were found in three genes (CDK12, AR, and SPOP). In addition, three variants of uncertain significance (DDR2 R128C, SRC P428L, and HNRNPU K574Sfs*32) were identified, which to the best of our knowledge have not been previously reported. Our results support the power of an immunohistochemistry panel including Arg-1 and HepPar1 when HC is suspected, and highlight the value of cytology for comprehensive diagnostic evaluation.

Refractory Splenic Marginal Zone Lymphoma Responsive to Combination Venetoclax and Bortezomib (Velcade) (V2) Therapy

Standard treatment regimens for the management of patients with refractory splenic marginal zone lymphoma (SMZL) are currently unavailable. Here, we report a case of SMZL, which, after failing multiple therapeutics, demonstrated an impressive clinical response to combined Venetoclax and Velcade (V²), a treatment combination currently being investigated in the setting of refractory multiple myeloma. We also report a unique histopathology and mutational profile that may have important implications for the characterization and prognosis of SMZL.

Enhanced carbonic anhydrase expression with calcification and fibrosis in bronchial cartilage during COPD

Pulmonary cartilage plays a crucial structural role determining the physiologic airway compressibility and distensibility, necessary for proper mechanical function. This functionality deteriorates with aging due to increased stiffness of both airway muscle and cartilage, as well as, decreased renewal capacity. Altered airway remodeling has been suggested as a pathogenic driver of chronic obstructive pulmonary disease (COPD) through mechanisms still incompletely understood. Using paraffin-embedded lung tissue sections from archived autopsy material from COPD with non-COPD age matched controls a histopathologic analysis focused on inflammation, fibrosis and calcification was performed with special stains (Masson's trichrome and Von Kossa) and immunohistochemistry for carbonic anhydrase IV (CA IV) and Ki-67. COPD lung tissues showed increased peribronchial inflammation compared to the non-COPD. Coarse amphophilic crystalline deposits in bronchial cartilage were more frequently observed in COPD sections, which were compatible with early dystrophic calcification of the extracellular matrix and chondrocytes. Moreover, Von Kossa staining revealed a significant calcium deposition in the cartilages from COPD in comparison to the controls. Interestingly, Ki-67 immunostains demonstrated a higher overall proliferative rate, including epithelial cells, in COPD. Furthermore, Masson's trichrome staining revealed relatively increased peribronchial collagen deposition associated with a fibrotic stromal response, which may be secondary to the inflammatory milieu in COPD. To further characterize the tissue microenvironment associated with dystrophic calcification, immunohistochemistry for CA IV was used, revealing significantly increased expression in chondrocytes and peribronchial tissue in COPD. Our findings demonstrate that dystrophic calcification of the extracellular matrix and chondrocytes can be linked to CA IV expression in COPD and suggest that pH changes in pulmonary tissue associated with inflammation and calcification may play an active role in COPD.

Introduction to a Special Issue on Low-Grade B Cell Lymphoma in the Spleen

Malignant lymphoproliferative disorders in the spleen may be primary (usually designated as splenic lymphoma) or secondary (due to progression of nodal or extra nodal lymphoid neoplasms) and represent an underestimated cause of splenomegaly, partially due to the decreasing frequency of splenectomy in our era of personalized molecular medicine [...]

A Review on Splenic Diffuse Red Pulp Small B-Cell Lymphoma

Splenic diffuse red pulp small B-cell lymphoma (SDRPL) is a rare disease, representing <1% of all non-Hodgkin lymphomas (NHL). The most common clinical manifestations include splenomegaly, lymphocytosis, and hemocytopenia. A diagnosis of SDRPL can be challenging, as it shares multiple clinical and laboratory features with splenic marginal zone lymphoma (SMZL), hairy cell leukemia (HCL), and HCL variant (HCL-v). Obtaining splenic tissue remains the gold standard for diagnosis. In the cases where splenic tissue is not available, diagnosis can be established by a review of peripheral blood and bone marrow studies. SDRPL is characterized by a diffuse involvement of the splenic red pulp by monomorphous small-to-medium sized mature B lymphocytes effacing the white pulp. The characteristic immunophenotype is positive for CD20, DBA.44 (20 to 90%), and IgG, and typically negative for CD5, CD10, CD23, cyclin D1, CD43, annexin A1, CD11c, CD25, CD123, and CD138. The Ki-67 proliferative index is characteristically low. Cyclin D3 is expressed in the majority of SDRPL in contrast with other types of small B-cell lymphomas, thus facilitating the recognition of this disease. There is no standard treatment regimen for SDRPL. Initial treatment options include splenectomy, rituximab monotherapy, or a combination of both. Chemoimmunotherapy should be considered in patients with advanced disease at baseline or progression.

Low-Grade Primary Splenic CD10-Positive Small B-Cell Lymphoma/Follicular Lymphoma

Primary splenic lymphoma (PSL) is a rare malignancy representing about 1% of all lymphoproliferative disorders, when using a strict definition that allows only involvement of spleen and hilar lymph nodes. In contrast, secondary low-grade B-cell lymphomas in the spleen, such as follicular lymphomas (FL), lymphoplasmacytic lymphoma and chronic lymphocytic leukemia/ small lymphocytic lymphoma, particularly as part of advanced stage disease, are more common. Indolent B cell lymphomas expressing CD10 almost always represent FL, which in its primary splenic form is the focus of this review. Primary splenic follicular lymphoma (PSFL) is exceedingly infrequent. This type of lymphoproliferative disorder is understudied and, in most cases, clinically characterized by splenomegaly or cytopenias related to hypersplenism. The diagnosis requires correlation of histopathology of spleen, blood and/or bone marrow with the correct immunophenotype (determined by flow cytometry and/or immunohistochemistry) and if necessary, additional molecular profiling. Management of this incurable disease is evolving, and splenectomy remains the mainstream treatment for stage I PSFL.

How to Diagnose and Treat CD5-Positive Lymphomas Involving the Spleen

Patients with CD5-expressing lymphomas presenting with splenomegaly are frequently diagnosed with chronic lymphocytic leukemia. The most important differential diagnosis is mantle cell lymphoma, both in its classical and leukemic, non-nodal forms, given its prognostic and therapeutic implications. Other small B-cell neoplasms that frequently involve the spleen and occasionally express CD5 include the splenic marginal zone lymphoma, hairy cell leukemia and, rarely, lymphoplasmacytic lymphoma. The frequency of CD5 positivity depends in part on the sensitivity of the detection methods employed. Usually, a combination of morphological, immunophenotypic and molecular findings allows for a precise sub-classification of CD5-positive, low-grade B-cell lymphomas of the spleen. Some of these tumors may display a mixture of small and larger B cells, raising the possibility of more aggressive lymphomas, such as diffuse large B-cell lymphomas (DLBCL). Approximately 5-10% of DLBCL are CD5-positive and some may manifest as primary splenic lesions. When available, the morphology of DLBCL in the splenic tissue is distinctive and a leukemic picture is very rare. In conclusion, the appropriate morphological and clinical context assisted by flow cytometry panels and/or immunohistochemistry allows the differential diagnosis of CD5-positive, non-Hodgkin, B-cell lymphomas involving the spleen.

Indolent CD8-positive T-cell lymphoid proliferation of the ear: a report of two cases

The current classification of primary cutaneous T-cell lymphoma (CTCL) of the World Health Organization (WHO) includes primary cutaneous CD8-positive aggressive epidermotropic cytotoxic T-cell lymphoma as a provisional entity awaiting cumulative data. Recent reports identify CD3/CD8-positive clonal T-cell lymphoid proliferations arising in the ear and nose that behave indolently and therefore defy currently established subclassification. Here, we report two cases of clonal CD8-positive/granzyme-B-negative T-cell lymphoid proliferations that arose in the ear and behaved indolently. Collectively, these cases suggest that an additional category of cutaneous indolent CD8-positive T-cell lymphoma may be necessary among the existing classification schemes.

Squamous cell carcinomatous meningitis

A case of leptomeningeal carcinomatosis due to a poorly differentiated malignancy is presented. Immunohistochemistry was used to characterize it as a squamous cell carcinoma. Squamous cell carcinomas rarely invade the meninges. There are few well-founded guidelines for managing patients with this condition. Prognosis is generally poor. A literature review of this entity is provided.

Auer rod-like inclusions in a low-grade B-cell leukemia

Auer rods define neoplastic blasts of myeloid origin. However, azurophilic, needle-shaped, Auer rod-like inclusions have rarely been reported in the neoplastic cells of patients with B-cell malignancies, including chronic lymphocytic leukemia/small lymphocytic lymphoma. Here, we report a case of low-grade B-cell leukemia most consistent with chronic lymphocytic leukemia/small lymphocytic lymphoma that displayed numerous intracytoplasmic, needle-shaped, azurophilic rods resembling Auer rods. Furthermore, we review the literature on Auer rod-like structures in B-cell neoplasms.

Concurrent diagnoses of Hodgkin lymphoma and biclonal myeloma in the bone marrow

The diagnoses of Hodgkin lymphoma and multiple myeloma have rarely been made simultaneously in the same patient. We present a case of an 82-year-old man who rapidly developed pancytopenia and liver failure with coagulopathy. Serum protein electrophoresis and immunofixation revealed an unequivocal immunoglobulin Gkappa and immunoglobulin Glambda biclonal gammopathy. Bone marrow biopsy showed involvement by classic Hodgkin lymphoma with an inflammatory background including 49% mature plasma cells. Unfortunately, the patient died 14 days after admission. To our knowledge, a case of concurrent Hodgkin lymphoma and biclonal multiple myeloma has not previously been reported. Detection of severe bone marrow plasmacytosis in the background of Hodgkin lymphoma should alert the pathologist to the possibility of collision with a plasma cell neoplasm, warranting a complete diagnostic workup.

Enteropathy-type T-cell Lymphoma After Intestinal Diffuse Large B-cell Lymphoma

A rare case of enteropathy-type T-cell lymphoma (ETL) developed in a 47-year-old Chinese male 6 years after the diagnosis of diffuse large B-cell lymphoma (DLBCL) in the small intestine. The patient initially presented with vague gastrointestinal complaints. Work-up demonstrated an ulcerated mass in the small intestine. Partial resection and histologic examination of the intestine showed a DLBCL, positive for CD20 and Bcl-2, involving the jejunum transmurally. Further staging work-up demonstrated mesenteric and retroperitoneal lymphadenopathy, splenomegaly, and ascites. The patient was treated aggressively with radiotherapy, chemotherapy, and autologous bone marrow transplant, and complete remission was obtained. Six years later, the patient presented with diarrhea and dehydration. Clinical work-up revealed thickening of the small intestinal wall, and biopsies demonstrated ETL based on morphology, immunohistochemistry, and polymerase chain reaction analysis. Celiac disease was diagnosed concurrently. The patient responded to chemotherapy, received allogeneic peripheral blood stem cell transplantation from an HLA-matched sibling donor, and remains in remission. To our best knowledge, this is the first reported case of metachronous ETL and DLBCL. Possible associations between the 2 types of lymphoma are discussed.

Ewing sarcoma family of tumors in unusual sites: confirmation by rt-PCR

Ewing sarcoma family tumors originating in the palate or adrenal gland are extremely rare and may cause difficulty in diagnosis. More common tumors primary to these sites need to be excluded before one arrives at the correct diagnosis. We have recently diagnosed 2 such cases. The 1st case was that of a 24-year-old woman who presented with a swelling in the right side of the hard palate. The 2nd case was diagnosed in a 28-year-old woman who presented with a mass in the right adrenal gland. In both cases, the diagnosis of Ewing sarcoma family of tumors was confirmed by immunohistochemical studies and reverse transcriptase-polymerase chain reaction (RT-PCR). The hard palate case is the 1st and the adrenal gland the 3rd case of Ewing sarcoma family of tumors arising in these sites, in which the diagnosis was confirmed by RT-PCR and/or cytogenetics. Accurate diagnosis of Ewing sarcoma family of tumors is crucial for the management of patients, and when found in such rare locations, diagnosis should be supported by immunohistochemical and/or molecular genetic studies.

The pathology of NK-cell lymphomas and leukemias

Natural killer (NK) cell lymphomas and leukemias are a rare but clinically important group of neoplasms. Most of these tumors are aggressive, with a high rate of mortality. They include extranodal NK/T-cell lymphomas of nasal type and aggressive NK-cell leukemias. Both are Epstein-Barr virus (EBV) associated and show similar epidemiologic features. A closely related entity seen mainly in children is hydroa vacciniforme-like lymphoma, which also is EBV positive. EBV influences the pathophysiology of these tumors, through the induction of cytokines and chemokines. The differential diagnosis of NK-cell malignancies includes fulminant EBV-associated T-cell lymphoproliferative disorder, a condition referred to in the past as fatal infectious mononucleosis. Benign proliferations of NK cells can be seen in association with viral infection. The disease formerly referred to as blastic NK-cell lymphoma is now considered to be a malignancy derived from a dendritic cell precursor.

Aminoacylase 1 is a sphingosine kinase 1-interacting protein

Sphingosine kinase type 1 (SphK1) and its product sphingosine-1-phosphate have been shown to promote cell growth and inhibit apoptosis of tumor cells. In an effort to further understand the regulation of SphK1, we used a yeast two-hybrid screen to find SphK1-interacting proteins. One of these was identified as aminoacylase 1 (Acy1), a metalloenzyme that removes amide-linked acyl groups from amino acids and may play a role in regulating responses to oxidative stress. Both the C-terminal fragment found in the two-hybrid screen and full-length Acy1 co-immunoprecipitate with SphK1. Though both C-terminal and full-length proteins slightly reduce SphK1 activity measured in vitro, the C-terminal fragment inhibits while full-length Acy1 potentiates the effects of SphK1 on proliferation and apoptosis. Interestingly, Acy1 induces redistribution of SphK1 as observed by immunocytochemistry and subcellular fractionation. Collectively, our data suggest that Acy1 physically interacts with SphK1 and may influence its physiological functions.

Sphingosine kinase type 2 is a putative BH3-only protein that induces apoptosis

There are two isoforms of sphingosine kinase (SphK) that catalyze the formation of sphingosine 1-phosphate, a potent sphingolipid mediator. Whereas SphK1 stimulates growth and survival, here we show that SphK2 enhanced apoptosis in diverse cell types and also suppressed cellular proliferation. Apoptosis was preceded by cytochrome c release and activation of caspase-3. SphK2-induced apoptosis was independent of activation of sphingosine 1-phosphate receptors. Sequence analysis revealed that SphK2 contains a 9-amino acid motif similar to that present in BH3-only proteins, a pro-apoptotic subgroup of the Bcl-2 family. As with other BH3-only proteins, co-immunoprecipitation demonstrated that SphK2 interacted with Bcl-xL. Moreover, site-directed mutation of Leu-219, the conserved leucine residue present in all BH3 domains, markedly suppressed SphK2-induced apoptosis. Hence, the apoptotic effect of SphK2 might be because of its putative BH3 domain.

Sphingosine kinase type 1 promotes estrogen-dependent tumorigenesis of breast cancer MCF-7 cells

The sphingolipid metabolite, sphingosine-1-phosphate (S1P), formed by phosphorylation of sphingosine, has been implicated in cell growth, suppression of apoptosis, and angiogenesis. In this study, we have examined the contribution of intracellular S1P to tumorigenesis of breast adenocarcinoma MCF-7 cells. Enforced expression of sphingosine kinase type 1 (SPHK1) increased S1P levels and blocked MCF-7 cell death induced by anti-cancer drugs, sphingosine, and TNF-alpha. SPHK1 also conferred a growth advantage, as determined by proliferation and growth in soft agar, which was estrogen dependent. While both ERK and Akt have been implicated in MCF-7 cell growth, SPHK1 stimulated ERK1/2 but had no effect on Akt. Surprisingly, parental growth of MCF-7 cells was only weakly stimulated by S1P or dihydro-S1P, ligands for the S1P receptors which usually mediate growth effects. When injected into mammary fat pads of ovariectomized nude mice implanted with estrogen pellets, MCF-7/SPHK1 cells formed more and larger tumors than vector transfectants with higher microvessel density in their periphery. Collectively, our results suggest that SPHK1 may play an important role in breast cancer progression by regulating tumor cell growth and survival.

Inhibitor specificity of recombinant and endogenous caspase-9

Apoptosis triggered through the intrinsic pathway by radiation and anti-neoplastic drugs is initiated by the activation of caspase-9. To elucidate control mechanisms in this pathway we used a range of synthetic and natural reagents. The inhibitory potency of acetyl-Asp-Glu-Val-Asp-aldehyde ('Ac-DEVD-CHO'), benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone ('Z-VAD-FMK') and the endogenous caspase inhibitor X-chromosome-linked inhibitor of apoptosis protein ('XIAP') against recombinant caspase-9 were predictive of the efficacy of these compounds in a cell-free system. However, the viral proteins CrmA and p35, although potent inhibitors of recombinant caspase-9, had almost no ability to block caspase-9 in this system. These findings were also mirrored in cell expression studies. We hypothesize that the viral inhibitors CrmA and p35 are excluded from reacting productively with the natural form of active caspase-9 in vivo, making the potency of inhibitors highly context-dependent. This is supported by survival data from a mouse model of apoptosis driven by Sindbis virus expressing either p35 or a catalytic mutant of caspase-9. These results consolidate previous findings that CrmA is a potent inhibitor of caspase-9 in vitro, yet fails to block caspase-9-mediated cell death.