  We introduce a multi-species diffuse interface model for tumor growth,
characterized by its incorporation of essential features related to chemotaxis,
angiogenesis and proliferation mechanisms. We establish the weak well-posedness
of the system within an appropriate variational framework, accommodating
various choices for the nonlinear potentials. One of the primary novelties of
the work lies in the rigorous establishment of the existence of a weak solution
through the introduction of delicate approximation schemes. To our knowledge,
this represents a novel advancement for both the intricate
Cahn-Hilliard-Keller-Segel system and the Keller-Segel subsystem with source
terms. Moreover, when specific conditions are met, such as having more regular
initial data, a smallness condition on the chemotactic constant with respect to
the magnitude of initial conditions and potentially focusing solely on the
two-dimensional case, we provide regularity results for the weak solutions.
Finally, we derive a continuous dependence estimate, which, in turn, leads to
the uniqueness of the smoothed solution as a natural consequence.
