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Study Demonstrates Paclitaxel Treatment Promotes Breast Cancer Dissemination and Metastasis in a Mena-dependent Manner

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MetaStat, Inc. (OTCQB:MTST), a personalized medicine company
developing therapeutic and diagnostic treatment solutions for cancer
patients, announced today results from a study published online on July
5, 2017 in Science Translational Medicine authored by MetaStat
collaborators from the Albert Einstein College of Medicine and
Montefiore Medical Center. This study demonstrated certain types of
chemotherapy promote breast cancer tumor cell dissemination and
metastasis, including increased circulating tumor cells (CTCs) and TMEM
or MetaSite™ scores (MS), in addition to enhanced expression of
pro-metastatic Mena protein isoforms. Consistent with the known
requirements for Mena in breast cancer metastasis, paclitaxel-induced
dissemination was found to be dependent on Mena protein expression.
Previous studies had demonstrated that animals grafted with MMTV-PyMT
Mena-null breast cancer tumors fail to develop CTCs or lung metastasis,
and paclitaxel-treatment did not promote metastasis of Mena-deficient
tumors in the current study.

"These data provide insight into why some patients with pathologic
complete responses (pCR) following chemotherapy do not derive long-term
benefit," stated Douglas A. Hamilton, MetaStat President and CEO. "As we
accelerate our therapeutic program aimed at preventing aggressive cancer
from spreading, we are further encouraged by the potential added benefit
to patients of combination therapy with taxanes and Mena-targeted drugs
to block chemotherapy-induced cancer cell dissemination and metastasis,"
said Mr. Hamilton.

"The ability to accurately define a pro-metastatic phenotype has the
potential to provide important and useful information towards the
effective management of patients newly diagnosed with breast cancer,"
stated Michael J. Donovan, MD, PhD, MetaStat acting Chief Medical
Officer.

The investigators used the research version of MetaStat's clinically
validated and CLIA-approved MetaSite Breast™ test to quantify
changes in the number of MetaSites before and after
chemotherapy treatment. In tumor samples from breast cancer patients,
neoadjuvant chemotherapy (NEC) consisting of paclitaxel after
doxorubicin plus cyclophosphamide increased MetaSite scores
(MS) and expression of the pro-metastatic MenaINV isoform.
Preclinical studies of patient-derived xenograft and PyMT murine models
also demonstrated that chemotherapy increased the density of MetaSites
and levels of the MenaINV isoform. The publication can be
found at http://stm.sciencemag.org/content/9/397/eaan0026.
A previous study, also by MetaStat collaborators, reported that Mena
expression confers resistance to paclitaxel in vitro and in
xenograft tumors and taxane therapy increased expression of
pro-metastatic Mena isoforms (i.e. MenaINV). The publication
can be found at http://mct.aacrjournals.org/content/16/1/143.long.

About the MetaSite Breast™ Test

The MetaSite Breast™ test is intended for use in patients with
early stage (stage 1-3), invasive breast cancer who have node-negative
or node positive, Hormone Receptor (HR)-positive, HER2-negative disease.
Clinical studies have demonstrated the MetaSite score (MS) is
significantly associated with increased risk of cancer metastasis.
MetaSite Breast™ is an analytically validated, fully automated
digital pathology assay that identifies Mena expressing tumor cells in
direct contact with CD68+ perivascular macrophages and CD31+ endothelial
cells ("MetaSites"). MetaSites have been shown to be the portal of entry
for cancer cells into the blood stream contributing to the development
of cancer metastasis. The MetaSite Breast™ assay is
performed on standard formalin-fixed paraffin-embedded (FFPE) tissue,
analytically validated under CLIA and clinically available through
MetaStat's CLIA-certified commercial laboratory.

About MetaStat, Inc.

MetaStat is a biotechnology company focused on discovering and
developing personalized therapeutic and diagnostic treatment solutions
for cancer patients. Our Mena isoform "driver-based" diagnostic
biomarkers also serve as novel therapeutic targets for anti-metastatic
drugs. MetaStat is developing therapeutic product candidates and paired
companion diagnostics based on a novel approach that makes the Mena
isoform protein a drugable target. Our core expertise includes an
understanding of the mechanisms and pathways that drive tumor cell
invasion and metastasis, as well as drug resistance to certain targeted
therapies and cytotoxic chemotherapies. MetaStat is based in Boston, MA.

Forward-Looking Statements

This press release contains "forward-looking statements" within the
meaning of Section 27A of the Securities Act of 1933, as amended, and
Section 21E of the Securities Exchange Act of 1934, as amended, and such
forward-looking statements are made pursuant to the safe harbor
provisions of the Private Securities Litigation Reform Act of 1995. You
are cautioned that such statements are subject to a multitude of risks
and uncertainties that could cause future circumstances, events or
results to differ materially from those projected in the forward-looking
statements as a result of various factors and other risks, including
those set forth in the company's Form 10-K and its other filings filed
with the Securities and Exchange Commission. You should consider these
factors in evaluating the forward-looking statements included herein,
and not place undue reliance on such statements. The forward-looking
statements in this release are made as of the date hereof and the
company undertakes no obligation to update such statements.

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