Protocol for Studying Embryonic Mammary Gland Branching Morphogenesis Ex Vivo

Mammary gland development starts during embryogenesis, and the process continues after birth. During development, the mammary gland undergoes massive morphological and physiological alterations including growth, invasion, and branching morphogenesis providing an ideal model for stem cell and cancer biology studies. Great efforts have been made in understanding mammary gland development during puberty and adulthood; however, the process during embryogenesis is still elusive. One reason is that the tools to study tissue dynamics during development are limited, which is partially due to the lack of an ex vivo culture method. Here we describe an updated organ culture protocol of the murine embryonic mammary gland. This powerful tool allows monitoring of growth and branching morphogenesis of mammary gland ex vivo by live imaging. In addition, we introduce a novel method for culturing intact, stroma-free mammary rudiments from late gestation mouse embryos in 3D in Matrigel. This approach can be used to identify the direct stromal cues for branching morphogenesis.

Hepsin regulates TGFβ signaling via fibronectin proteolysis

Transforming growth factor‐beta (TGFβ) is a multifunctional cytokine with a well‐established role in mammary gland development and both oncogenic and tumor‐suppressive functions. The extracellular matrix (ECM) indirectly regulates TGFβ activity by acting as a storage compartment of latent‐TGFβ, but how TGFβ is released from the ECM via proteolytic mechanisms remains largely unknown. In this study, we demonstrate that hepsin, a type II transmembrane protease overexpressed in 70% of breast tumors, promotes canonical TGFβ signaling through the release of latent‐TGFβ from the ECM storage compartment. Mammary glands in hepsin CRISPR knockout mice showed reduced TGFβ signaling and increased epithelial branching, accompanied by increased levels of fibronectin and latent‐TGFβ1, while overexpression of hepsin in mammary tumors increased TGFβ signaling. Cell‐free and cell‐based experiments showed that hepsin is capable of direct proteolytic cleavage of fibronectin but not latent‐TGFβ and, importantly, that the ability of hepsin to activate TGFβ signaling is dependent on fibronectin. Altogether, this study demonstrates a role for hepsin as a regulator of the TGFβ pathway in the mammary gland via a novel mechanism involving proteolytic downmodulation of fibronectin.

Abstract LB-204: Oncogenic Ras signaling requires serine protease hepsin to induce invasive breast cancer phenotype

Invasive cancer growth occurs when epithelial tumor cells individually or collectively detach from the primary tumor and migrate into the adjacent healthy tissue. This process starts a gradual tumor progression that may lead to life-threatening metastatic disease. Hepsin is a type II transmembrane serine protease that is frequently overexpressed in breast, prostate, and other epithelial cancers. It promotes tumor progression through activating growth factors and disrupting cell-cell and cell-basement membrane (BM) junctions. Although hepsin participates in pericellular cancer degradome, the oncogenic upstream mechanisms that activate hepsin in cancer are not well known. We found that oncogenic Ras proteins by activating MAPK pathway signaling alter the ratio of hepsin and HAI-1 to increase the proteolytic activity of hepsin. In 3D epithelial culture models of Ras-driven cancer, depletion of hepsin by shRNA restored desmosomes, BM defects, and glandular morphology but not the apical polarity. Mechanistically, Ras-MAPK pathway affected hepsin/HAI-1 via two distinct downstream pathways: Hepsin protein was stabilized via Ras-induced and heat shock transcription factor-1-mediated stress pathway, whereas HAI-1 was down-regulated by Ras via tumor suppressor LKB1 and PI3K-dependent pathways. Altogether, the results suggest that abnormal activation of Ras-MAPK pathway elevates hepsin activity to execute early steps of breast cancer invasion.

Citation Format: Shishir Mani Pant, Topi Tervonen, Denis Belitskin, Johanna Englund, Emmy Verschuren, Panu Kovanen, Juha Klefstrom. Oncogenic Ras signaling requires serine protease hepsin to induce invasive breast cancer phenotype [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-204.

Abstract 3484: Ras recruits oncogenic serine protease hepsin to disrupt mammary epithelial integrity

Type II transmembrane serine protease hepsin is overexpressed and redistributed in clinical breast cancer samples, although the HPN gene is not a frequent target of cancer-specific genetic alterations. Here, we sought to identify cancer relevant upstream factors responsible for oncogenic deregulation of hepsin. We explored the effects of ectopic expression of major oncogenes and tumor suppressors on hepsin protein expression levels in non-malignant mammary epithelial cells, finding that HrasV12, KrasV12, ectopic wild-type Kras, endogenous mutant KrasD12 and E2F-1 induce the expression of active form of hepsin. Oncogenic Ras proteins also reduced expression levels of cognate hepsin inhibitor, HAI-1. Concomitantly, oncogenic Ras expression led to disappearance of desmoplakin and desmoglein 2 from desmosomal junctions, which correlated with mislocalization of hepsin from its predominant localization in desmosomes to cytosol. To explore the effects of mutated Ras expressed at endogenous levels we used lung tumors derived from lox-stop-lox (LSL)-KrasD12; p53-/- and LSL-KrasV12 mammary epithelial structures in ex vivo 3D cultures. In both cases, hepsin was highly expressed and predominantly localized to cytosol. Knockdown of hepsin by shRNA rescued HrasV12-induced epithelial integrity defects in mammary epithelial 3D culture and furthermore, MEK and ERK inhibitors prevented HrasV12-induced hepsin deregulation as well as desmosomal and basement membrane defects. Critical pathways downstream of MAPK pathway are being studied and will be discussed. These findings suggest a critical role for hepsin in mediating Ras-MAPK-mediated disruption of epithelial integrity during tumorigenesis.

Citation Format: Topi A. Tervonen, Shishir M. Pant, Denis Belitskin, Johanna Englund, Katja Närhi, Emmy Verschuren, Panu Kovanen, Juha Klefström. Ras recruits oncogenic serine protease hepsin to disrupt mammary epithelial integrity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3484.

European Network of Breast Development and Cancer turned 10 years: a growing family of mammary gland researchers

The European Network for Breast Development and Cancer (ENBDC), a worldwide network (http://www.enbdc.org/), celebrated its tenth anniversary with a fantastic meeting last March 15–17, 2018 in Weggis with 76 attendees.

Effect of highly active antiretroviral therapy on the serological response to additional measles vaccinations in human immunodeficiency virus-infected children

Children infected with human immunodeficiency virus (HIV) often lose their vaccine-induced antibody to measles virus. Before highly active antiretroviral therapy (HAART), an additional immunization against measles infrequently resulted in protective antibodies. The antibody response to an additional measles-mumps-rubella (MMR) vaccination was compared in 28 HIV-infected children who lacked protective antibody to measles virus and were undergoing HAART or non-HAART regimens. Serostatus was measured by automated enzyme-linked immunoassay. Nine (64.3%) of 14 children undergoing HAART, compared with 3 (21.4%) of 14 in the non-HAART group, had antibody to measles virus after the additional vaccination with MMR (P=.027). The groups showed no significant difference in CD4 cell values. Ten of 14 HAART patients had undetectable levels of HIV. The mean HIV load for the HAART group was 27,700 copies/mL (median, <400 copies/mL); for the non-HAART group, it was 86,000 copies/mL (median, 9000 copies/mL). Thus, HAART improves the response to an additional MMR vaccination, which is consistent with immune system reconstitution.

Respiratory syncytial virus upper respiratory tract illnesses in adult blood and marrow transplant recipients: combination therapy with aerosolized ribavirin and intravenous immunoglobulin

Respiratory syncytial virus (RSV) is an important cause of serious respiratory illness in blood and marrow transplant (BMT) recipients. In some subsets of these immunocompromised patients, RSV upper respiratory illnesses frequently progress to fatal viral pneumonia. The frequency of progression to pneumonia is higher during the pre-engraftment than during the post-engraftment period. Once pneumonia develops, the overall mortality is 60-80%, regardless of the treatment strategy. We performed a pilot trial of therapy of RSV upper respiratory illnesses using aerosolized ribavirin and IVIG (500 mg/kg every other day), with the goal of preventing progression to pneumonia and death. Two dosages of ribavirin were used: a conventional regimen (6 g/day at 20 mg/ml for 18 h/day) and a high-dose short-duration regimen (6 g/day at 60 mg/ml for 2 h every 8 h). Fourteen patients were treated for a mean of 13 days (range: 7-23 days). In 10 (71%) patients, the upper respiratory illness resolved. The other four (29%) patients, three of whom were in the pre-engraftment period, developed pneumonia, which was fatal in two. The most common adverse effect was psychological distress at being isolated within a scavenging tent. In conclusion, prompt therapy of RSV upper respiratory illnesses in BMT recipients with a combination of aerosolized ribavirin and IVIG was a safe and promising approach to prevent progression to pneumonia and death.

Rhinovirus infections in myelosuppressed adult blood and marrow transplant recipients

Scant data are available on the clinical significance of rhinovirus infections in immunocompromised patients. We reviewed the clinical courses of and outcomes for 22 myelosuppressed adult blood and marrow transplant recipients with rhinovirus infections who were hospitalized at the M.D. Anderson Cancer Center (Houston) from January 1992 to January 1997. In 15 patients (68%), illnesses remained confined to the upper respiratory tract. Seven patients (32%) developed fatal pneumonia. These patients had profound respiratory failure a mean of 12 days (range, 3-21 days) after the onset of symptoms. In six of these seven cases, rhinovirus was isolated before death from a bronchoalveolar lavage fluid specimen and/or an endotracheal aspirate. Five patients underwent autopsies, one of which revealed disseminated aspergillosis and four of which revealed interstitial pneumonitis and/or acute respiratory distress syndrome and no other organisms. In conclusion, rhinovirus infections may be associated with considerable pulmonary-related morbidity and mortality in severely myelosuppressed immunocompromised patients.

Maternal immunization against viral disease

The protective effect of maternal antibody against many viral diseases has been recognized. The use of maternal immunization has been considered as a means to augment this protection in the young infant against disease. Advantages of maternal immunization include the fact that young infants are most susceptible to infections but least responsive to vaccines, that pregnant women are accessible to medical care and respond well to vaccines, that IgG antibodies cross the placenta well during the third trimester, and that immunization of the pregnant woman has the potential to benefit both the mother and the infant. Disadvantages include the potential inhibition of an infant's response to active immunization or natural infection and liability issues with pharmaceutical companies and physicians. Immunization of pregnant women with viral vaccines for poliovirus, influenza viruses, and rubella has been described and maternal vaccination with these vaccines has been found to be safe for both the mother and the fetus. An open-label study of post-partum women immunized with the purified fusion protein of RSV (PFP-2, Wyeth-Lederle Pediatrics and Vaccines, Inc., Pearl River, NY) demonstrated that the vaccine was non-reactogenic and immunogenic; RSV-specific antibody was detected in breast milk. Immunization of pregnant women with purified protein or subunit vaccines could be considered against neonatal viral pathogens, such as respiratory syncytial virus, parainfluenza viruses, herpes group viruses, and human immunodeficiency virus. Further studies are needed to define the safety and efficacy of maternal immunization.

Influenza among hospitalized adults with leukemia

Influenza is one of the most important respiratory diseases of mankind, yet scant data exist concerning the frequency and clinical course of influenza in severely immunocompromised adults. From October 1993 to September 1994, we cultured the respiratory secretions of all adults with leukemia who were hospitalized with an acute respiratory illness at The University of Texas M.D. Anderson Cancer Center in Houston. During a 9-week period from 29 November 1993 to 29 January 1994, influenza virus type A (H3N2) was isolated from 15 (33%) of these 45 hospitalized adults. Twelve (80%) of the cases of influenza were associated with pneumonia, and four patients (33%) with pneumonia died. Patients who died tended to have received chemotherapy more recently and to be more myelosuppressed. Autopsy examination in two cases revealed histopathologic changes consistent with viral pneumonia. During community outbreaks, influenza is a frequent cause of serious respiratory disease in hospitalized adults with leukemia. Effective prophylactic and therapeutic regimens need to be defined for immunocompromised patients.

Nosocomial respiratory syncytial virus infections: prevention and control in bone marrow transplant patients

OBJECTIVE

To assess the effectiveness of a multifaceted infection control strategy in limiting the nosocomial transmission of respiratory syncytial virus (RSV) infection to patients in a bone marrow transplant (BMT) unit.

DESIGN

Before/after trial.

SETTING

University-affiliated tertiary cancer center.

PATIENTS

Adult BMT recipients hospitalized during two consecutive wintertime community outbreaks of RSV infection.

INTERVENTIONS

An infection control strategy against nosocomial RSV infection was implemented in the BMT unit in February 1993. The strategy involved prompt identification, isolation, and cohorting of RSV-infected patients; prompt therapy with aerosolized ribavirin; use of masks and gloves by anyone entering an infected BMT patient's room; screening visitors for respiratory symptoms; restricting visitation by all children under 12 years of age and all family members and other visitors with RSV symptoms; and restricting symptomatic hospital staff from working in the BMT unit.

RESULTS

After implementation of the multifaceted infection-control strategy, there were four cases of nosocomial RSV infection in 3,870 patient days (incidence density, 1.0 case/1,000 patient days) compared with 14 cases of nosocomial RSV infection in 3,152 patient days (incidence density, 4.4 cases/1,000 patient days) during the 1992-1993 RSV season (rate ratio, 4.4; 95% confidence interval [CI95]. 1.4-17.9: P < .01). This decrease in incidence occurred despite a comparable prevalence of community-acquired RSV cases between the two seasons (2.2% vs 3.2% in 1992-1993 and 1993-1994, respectively; prevalence ratio, 0.7; CI95, 0.2-2.1; P = 0.5).

CONCLUSION

Institution of a multifaceted infection control strategy significantly reduced the frequency of nosocomial RSV infection in a high-risk group of adult BMT recipients.

Respiratory disease due to parainfluenza virus in adult bone marrow transplant recipients

We reviewed the frequency and clinical course of parainfluenza virus (PIV) infections in 1,173 adult bone marrow transplant (BMT) recipients cared for at The University of Texas M.D. Anderson Cancer Center (Houston). Between January 1991 and September 1994, PIV was isolated from the respiratory secretions of 61 (5.2%) of these patients. Thirty-four (56%) of the 61 patients had uncomplicated upper respiratory tract illnesses and survived. The remaining 27 patients (44%) developed pneumonia, and the associated mortality was 37% (10 of 27 patients). Twenty-three (85%) of the patients with pneumonia had had preceding upper respiratory illnesses. Of the 10 patients who died, nine died within 100 days after transplantation. Histopathologic examination of lung tissue from seven patients revealed intracytoplasmic viral inclusions in six, a finding consistent with invasive PIV pneumonia, and viral changes in the seventh patient. Seven of the 10 patients who died had other serious concurrent infections. Of 42 patients who developed PIV infection early after transplantation (i.e., < 100 days), the frequency of pneumonia was higher among the 18 allogeneic BMT recipients (61%) than among the 24 autologous BMT recipients (42%), and the associated mortality was also higher (55% vs. 30%, respectively). PIVs are an important cause of life-threatening pneumonia in adult BMT recipients, particularly patients who have recently undergone allogeneic bone marrow transplantation.

Evaluation of centrifugation cultures of bronchoalveolar lavage fluid for the diagnosis of cytomegalovirus pneumonitis

Cytomegalovirus (CMV) pneumonitis is one of the most severe manifestations of CMV disease among immunocompromised patients. The diagnosis of CMV pneumonitis traditionally has required the use of invasive procedures such as lung biopsy. In this retrospective study, we evaluated a centrifugation culture method in samples of bronchoalveolar fluid for the noninvasive diagnosis of CMV pneumonitis. During a 9-mo period, 75 bronchoalveolar lavage samples were collected from 58 patients with pneumonitis. We analyzed the data from 21 patients in whom lung tissue samples were obtained within 14 days of the bronchoalveolar lavage. Centrifugation cultures of bronchoalveolar fluid were positive for CMV in 12 cases. CMV pneumonitis was confirmed in samples of lung tissue from five (42%) of the 12 patients, whereas no evidence of CMV pneumonitis was found in the remaining seven (58%) cases. Of nine patients with negative centrifugation cultures, CMV pneumonitis was confirmed in two (22%). When compared with conventional cultures, we found bronchoalveolar lavage fluid centrifugation cultures to be highly sensitive (100%) and specific (92%) for the detection of CMV infection. However, detection of CMV by centrifugation culture proved to be only moderately sensitive (71%) and nonspecific (50%) for the diagnosis of CMV pneumonitis.

A new hepato-pancreato-renal disorder resembling tyrosinemia involving neuropathy and abnormal metabolism of polyunsaturated acids

This report describes a new disorder resembling hereditary tyrosinemia (HT) but differing from it in several respects. Similarities include failure to thrive with hypoproteinemia, micronodular cirrhosis, alpha-fetoprotein positive hepatocellular carcinoma, renal Fanconi syndrome with renal tubular ectasia, hypermethioninemia, and hypoglycemia associated with islet cell hyperplasia. However, the tyrosine metabolic pathway was intact. Unique findings include optic atrophy, cerebellar degeneration, and exocrine pancreatic hypoplasia. Polyunsaturated fatty acid (PUFA) status was evaluated in the serum and liver. Initial PUFA profile to serum phospholipids revealed grossly elevated linoleic acid and subnormal linolenic acid. All PUFAs derived from these precursors were absent suggesting gross abnormalities in the utilization of these two essential fatty acids for synthesis of longer chain highly unsaturated structural PUFA. Analysis of liver phospholipids indicated that linoleic acid was lower and w3 and monenoic acids were higher than in the liver specimens from two cases of HT. The gross abnormalities in PUFA pattern, although perhaps secondary to another cause, represent serious structural and functional abnormalities of essential membrane lipids and potentially of eicosanoids derived from them.

Progressive mucocutaneous herpes simplex infection due to acyclovir-resistant virus in an immunocompromised patient: correlation of viral susceptibilities and plasma levels with response to therapy

Rapidly progressive disease due to acyclovir-resistant herpes simplex has not been described. We report such a case and detail successful patient management using viral sensitivities and plasma acyclovir levels to guide therapy. Response was correlated with plasma levels above those inhibiting viral growth by 50% (ID50) in vitro.